Progress report

Progress report

2002-2003

Edited by

Pedro W. Crous,

Robert A. Samson

and

Richard C. Summerbell

Centraalbureau voor Schimmelcultures

Fungal Biodiversity Centre

Centraalbureau voor Schimmelcultures - Fungal Biodiversity Centre.

Visiting and courier address: Uppsalalaan 8, 3584 CT Utrecht, The Netherlands.

Postal address: P.O. Box 85167, 3508 AD Utrecht, The Netherlands

Telephone +31(0)30 2122600. Telefax +31(0)30 2512097. Email: [email protected]

Homepage: http://www.cbs.knaw.nl

Contents

Preface ...4

Structure and Research Programmes ...6

The Collection...8

Research Programmes

Biodiversity & Ecology ...13

Indoor Air, Food and Applied Mycology ..16

Evolutionary Phytopathology ...19

Origins of Pathogenicity in Clinical Fungi 22

Comparative Genomics and

Bioinformatics ...25

Programmes, Themes and Projects

...28

Scientific Output (2002–2003) ...33

Contract Research and Services ...44

Finance and Staff ...47

Preface

It is with great pleasure that the Centraalbureau voor Schimmelcultures (CBS) presents its first biennial

progress report. It is also a great honour for us to present this report to the President of the Academy, Prof.

dr W.J.M. Levelt on the 13

th

of May 2004, on the very day that the CBS is celebrating its 100

th

centenary.

CBS, also known as the Fungal Biodiversity Centre, is a unique institute and international resource.

Although situated in the Netherlands and forming one of the institutes of the Royal Netherlands Academy of

Arts and Sciences (RNAAS), it is international in its scope and significance. It curates a major component of

the world’s fungal biodiversity, and is seen as a global research resource, an essential tool enabling

researchers to address specific questions and to prove or disprove hypotheses. In other words, we make

the fungal tree of life accessible to science.

There are no costs involved in depositing strains at the CBS,

and once these strains are deposited, they can be requested by the depositors for the purposes of their own

research, but at the same time, by agreement, they also become available to the rest of the scientific

community. CBS sees itself as an important resource for the international mycological community, a

resource that is owned in spirit by all mycologists who have ever deposited any material for preservation in

the collection. In essence, we are your living fungal DNA bank. CBS is no mere repository but is instead

an internationally active investment bank, participating, for example, in international ventures like the US

National Science Foundation (NSF)-funded Assembling the Fungal Tree of Life (AFToL) project.

The main focus of the institute is to collect, study and preserve living fungal biodiversity. To discover,

describe and then preserve for later generations is a major challenge, one that CBS has proudly taken up for

the past 100 years. Taxonomic research provides scientific knowledge about species, populations and

clones, and links these genotypes to correct names, which is the sine qua non of meaningful scientific

communication about organisms. In view of the current urgency to preserve valuable biodiversity in nature

and, in many cases, in cultivation, CBS is under extreme pressure to document and preserve as much of the

Fungal Kingdom as possible, to do this with cultures held in a biologically pristine, metabolically stable state.

To maximize the value of these cultures, we endeavour to produce and collect valuable new data sets for

these strains, and to make this information freely available in state-of-the-art online databases. In a nutshell,

CBS sees its collection as being a major component of the virtual laboratory of the future. The

information management involved in today’s big science poses even steadily greater challenges for the

future. At the base of all the information handling lies a highly vulnerable element, the investigated strain

itself, representing a small part of a population, i.e., of the species we are trying to preserve. Without

maintenance of this basis in living reality, all biological information handling loses value.

The CBS is also home of an important journal of systematics, the Studies in Mycology (SIM; current impact

factor 1.6), which publishes monographs on various groups, as well as issues dedicated to specific topics.

Because the RNAAS is supportive of the “Open Access” policy for scientific journals, CBS plans to launch

the SIM online during 2004, which will further boost readership, profile, and impact.

Although the CBS is currently one of the oldest and most valuable living biological resources of fungi in the

world, it must also embrace change and embrace new challenges, both scientific and technical, in regard to

finding ways to automate preservation methods within an ever-increasing collection. The investment that the

RNAAS has made in the CBS since we became an affiliated institute in 1968 is now paying off in a big

way, as the CBS currently represents a powerful research platform that interlinks scientists, teachers,

quarantine officers, physicians, corporations and biologically interested members of the public by placing

correct scientific information at their disposal. In the past, we used to wonder which fungal taxa occurred

where. In the future, we will ask which genotype or clone occurs at what longitude and latitude, and what

substrate it utilizes, what else utilizes that substrate, what the organism breaks down or produces, how its

occurrence influences the whole ecology of its environment, and what would happen if it were to become

extinct. To collect and preserve an optimal representation of these strains, and to create the databases

that will accurately reflect and manage all these data, is the exciting challenge we currently face.

A topic that remains a focus of major debate is the estimated number of fungal species making up our

world biodiversity. Whether there are 1.5 million fungi, as one estimate states, or whether even higher

numbers exist, one thing we do agree on is that of the 80 000-plus organisms that have been named to

date, only a small percentage has been successfully cultured and preserved in collections. CBS

encompasses more than 25% of the known culturable species. This is less than a drop in the ocean of the

diversity out there, especially if one takes into account that one strain does not represent the genetic

diversity occurring within a species. To answer the scientific questions of the future we need not only

quality, but also quantity of strains, namely populations that have been collected in a specific manner.

Such populations are essential, as real ecological, evolutionary and comparative genomics questions

cannot be addressed without them. Where do we find the scientists to collect the remaining, larger portion

of the fungal biodiversity still ‘out there;’ where will we find the funds to enable us to preserve all these

strains, and what is the envisaged time frame?

The world is ever changing, and so is the climate, which again influences the earth’s microbial biodiversity.

Fantastic challenges lie in wait, but we have to embrace them as a unified international scientific

community. One can argue that not to culture and preserve voucher material representing the fungi you

are working with is to leave the job half done; your work threatens to become an irreproducible result as

conceptual improvements reveal inadequacies in the names and other identifiers (e.g, specific DNA

sequences) you used. In this light, CBS represents a wonderful scientific opportunity, your own living

fungal bank, where the smallest investment will earn you scientific dividends for at least the next 100 years

of studies on fungal biodiversity and ecology.

Pedro W. Crous

Director,

Centraalbureau voor Schimmelcultures,

Structure and Research Programmes

22

The Fungal Biodiversity Centre is an institute of

biosystematics, with all research focused on its unique

living collection of fungi. Research projects strive to

add novel strains or species to the collection, or to

add valuable information, including genetic and other

datasets, to the records of strains already in the

collection. Although most projects are ecological in

nature, focusing on biodiversity issues, others strive to

unravel metabolomic, proteomic or genomic aspects

of specific fungal groups or species. Additional

information relating to these projects can be found

under the descriptions of specific research

programmes contained in this report.

CBS is an active partner in numerous national and

international collaborative projects, and aims to use

these projects to broaden its scope to include

functional fungal biodiversity. Related projects are on

a wide range of topics: evolutionary and

developmental biology of fungi; the elucidation of

structure, function and morphogenesis in

phylogenetically relevant cellular components; and the

exploration of developments in the “-omics” sciences.

As a partner of the Consortium for European

Taxonomic Facilities (CETAF), CBS is one of the

member institutes that were successful in obtaining

funding from an EU project aimed at facilitating

scientific exchange; this SYNTHESYS funding allows

systematic researchers from the EU and

EU-accession countries access to the collection and its

facilities over the next 5 years. Details pertaining to

SYNTHESYS can be found on our web page. CBS’s

success in obtaining other competitive EU funding is

shown not just by our currently active projects of the

European Biological Resource Centres Network

(EBRCN), but also by our success in obtaining two

new EU-funded projects. CBS also represents the

Netherlands in the Organisation for Economic

Co-operation and Development (OECD) ‘Biological

Resource Centres’ task force of the Working Party on

Biotechnology, and is on the council of the

Netherlands Biodiversity Information Network

(NL-BIF), which is the Dutch component of the Global

Biodiversity Information Network (GBIF).

Research activities can be divided into three areas,

each being served by different research programmes,

with their own themes and projects. The collection

and databases serve all research programmes, and

are central to all activities.

The

Collection

Green Biodiversity

Biodiversity & Ecology (R.C. Summerbell)

Evolutionary Phytopathology (P.W. Crous)

Clinical Biodiversity

Origins of pathogenicity in clinical fungi (G.S. de Hoog)

Comparative Genomics and Bioinformatics (T. Boekhout)

Industrial Biodiversity

Research collaboration

•

The CBS Collection of Fungi and Yeasts covers virtually all fungal groups that can be cultured, conserving the

world’s mycological biodiversity and documenting the wealth of our microbial natural resources. The number of

fun-gal strains at CBS is well over 48 000, giving this institute an unchallenged position as the major reference centre for

mycological research. The CBS Bacterial Collections harbour another 10 000 strains; one part of this bacterial

col-lection, the Plasmid and Phage Colcol-lection, is unique. The high quality of strains included in CBS is ensured by the

practise of having identities and typical features authenticated by CBS specialists. A wealth of morphological,

physio-logical, chemical and molecular data is connected with the strains. Use of these data allows researchers to make

predictions about the characters of newly identified isolates, and it also allows the general properties of particular

genetic lineages of fungi to be elucidated. In its most recent peer review, the CBS Collection received the rating:

‘ex-cellent’.

Two years ago, CBS moved from two locations in Baarn and Delft, the

Netherlands, to new quarters in Utrecht, and fused with the Netherlands

Culture Collection of Bacteria (NCCB) bacterial collections. The

amalga-mated CBS is now the largest culture collection worldwide dealing

primar-ily with fungal cultures. Including all filamentous fungi, yeasts, Oomycetes

and bacteria, there are more than 58 000 cultures in the collections. A

survey made at the ASM meeting in Washington last year showed that

scientists considered the CBS the best culture collection in Europe. This

reputation of quality leads to an increased demand to take over increasing

numbers of poorly supported, specialized collections as well as “orphaned

collections”. To cite just a few, we have taken responsibility for

substan-tial parts of the human fungal pathogen collection of the U.S. Centers for

Disease Control and Prevention (CDC), the predominantly Antarctic yeast

collection of Dr H. Vishniac, the specialized hyphomycete collections of

the University of Uppsala (Dr O. Constantinescu), and the Alejandro de

Humboldt Institute of the Cuban Academy of Sciences (Dr R.F.

Castañeda Ruíz), together with the plant-pathogenic fungal collection of

the University of Stellenbosch (Dr P. Crous). Newly acquired collections

led to the incorporation of 3500 new strains to CBS in 2003; this is over

three times the normal annual growth rate. This trend started in 2001 and

will continue in 2004 with the collections of Dr K. Hyde and Dr M.

Black-well.

The efficiency and quality of the CBS Collection is based on four major

factors, outlined below.

Modern laboratory facilities

. CBS possesses modern laboratory facilities

outfitted with cutting-edge equipment. Our institute was completely

reno-vated in 2000 and 2001 and now offers the best possible environment to

host a large culture collection and its associated research institute.

Preservation and quality control

. CBS has the ability to store the strains it

acquires in several of the most advanced available preservation methods.

Cryopreservation and freeze-drying are especially important. These

methods allow us to keep microorganisms in a condition that is as close

as possible to the original state in which they were received or collected.

Our preservation research programme has done outstanding work in the

development of lyoprotectants. One lyoprotectant developed by this

pro-gramme increased survival rates of fungi by up to 80% and increased

bacterial survival by a factor 15 000. Recently, the properties of this

pro-tectant in its dried state were studied by Differential Scanning Calorimetry

and Nuclear Magnetic Resonance

(in collaboration with the National

Institute for Public Health and

Envi-ronmental Protection [RIVM] and

Wageningen Agricultural University

[LUW], The Netherlands) and it

was found that its structure was

changed in such a way that

dam-age to the lipid structures making

up cell membranes and the

pro-teins was minimized. The

im-provements obtained from our

preservation research programme

are directly implemented in the

day-to-day procedures of the

cul-ture collection. Thanks to the

opti-mization of the cryopreservation

and lyophilization protocols we

were able to reduce the collection

of strains needing to be maintained

in active growth on agar media to

5% of the total size, with most of

the remaining active cultures

be-longing to a single difficult group,

the Oomycetes. Our recent

re-search has shown that even

Oo-mycetes can be cryopreserved

successfully. Stability of the

pre-served materials is monitored by

periodic moisture content and Tg

(glass-transition temperature)

measurements. A new freeze-dryer

(Christ Epsilon 2-80) was recently

acquired that is fully specified to

satisfy requirements for ISO 9001

certification and to conform to

Good Manufacturing Practice

(GMP) standards. Most

mechani-cal freezers in CBS have been

replaced by gas-phase liquid

ni-trogen containers. This new

technique, in which material is

preserved in a dynamic gas

phase maintained by a constant

flow of cold gas from above,

re-sults in temperatures that are

constantly below –180° C,

some-thing that is impossible to achieve

with a static gas phase.

Data management

. CBS has met

the need to partner the

acquisi-tion of large numbers of strains

with the development of accurate

strain management and

informa-tion systems. We have developed

Type of deposit

Proportion of orders of strains

The total amount of strains in the last three years

increased by 30%, the active agar collection

decreased by 65%.

Developments in the collection of Fungi and Yeast

stock management software

in-house allowing us to manage

all aspects of strain acquisition,

storage, and distribution, as

well as order-handling and

in-voicing. This software greatly

improves efficiency, and at the

same time also adds value to

the collection. Results of all

checks made on the strains are

recorded in the database,

al-lowing us to see whether or not

the quality of a strain remains

constant over the years.

Scien-tific information on the strains is

also recorded, as is elaborated

below in the section on

bioin-formatics and databasing.

Expertise.

A functional culture

collection is made up not just of

strains, hardware, and software

but also of people. This

essen-tial component is one of the

major strengths of the CBS. At

the technical level, highly

skilled and experienced

techni-cal staff employ both

conven-tional methods (morphological,

physiological) and new

molecu-lar technologies

(electrophore-sis methods, DNA sequencing

and, coming soon, DNA

microarrays) in their work with

fungi and bacteria. Our staff is

actively working on

prepara-tions for ISO 9001 certification.

This process is in its final stage

and it will be ready by June

2004. It will enable us to assure

our clients and end-users the

highest possible standards of

quality. At the scientific level,

our research staff also greatly

contributes to the wealth of the

collection by bringing new

methodologies, data and

exper-tise, not to mention isolates. An

incredible diversity of strains

has been acquired thanks to

the broad-ranging scientific

in-terests of our researchers.

These interests have also

sparked the development of

research programme s

essen-tial to leading collections,

in-cluding investigations into

phy-logeny, taxonomy and

nomen-clature, strain preservation

techniques, functional

genom-ics and bioinformatgenom-ics.

Research projects and

col-laborations

From a list of many projects,

let’s cite three major research

endeavours that were initiated

or co-initiated by the CBS

col-lection during the last 2 years.

•

Nomenclatural, taxonomic

and phylogenetic studies were

undertaken for the following

groups:

Aspergillus,

Debaryo-myces

,

Ganoderma,

Metschnikowia

(in collaboration

with Dr M. Herzberg from the

University of Marburg),

Pleo-sporales, Ptycho-gaster,

Yar-rowia

and

Zygoascus.

•

All type strains including

the type strains of species now

considered to be redundantly

described (synonymous

spe-cies names) have been or will

be sequenced and integrated

into a web-based system for

comparison and identification

based on BioloMICS software.

In 3 years of work (2001-2003),

we have already generated

more than 15 000 sequences of

selected ribosomal DNA

re-gions (the ITS1, 5.8S, ITS2 and

26S rDNA [D1,D2] regions).

• In the interlinked fields of

functional genomics and

bioin-formatics, a project is in

pro-gress in which complete fungal

genomes are compared to

elu-cidate phylogenetic and

func-tional trends. The intention is

to link evolution with the

devel-opment and change of

particu-lar metabolic and ontogenetic

functions. For this project, novel

software modules were

devel-oped that allow us to obtain a

better understanding of gene

expression in the organisms we

are working on.

The Netherlands government

(VROM) has made CBS

re-sponsible for control testing

aimed at detecting any

acciden-tal release of microbial

con-tamination in laboratories working

with Genetically Modified

Organ-isms.

International projects.

Our

re-searchers are also part of several

international projects including:

• the “Index Fungorum” project

(collaboration with CABI

Biosci-ence, UK) through which about

350 000 fungal names will be

post-ed on the Internet and will serve as

the fungal component in the

Cata-logue of Life (a component of of

the Species 2000 project and a

subproject of GBIF);

•

the “CBS-CABI CD-Rom”

pro-ject, meant to produce a catalog of

cultures and related data for the

two largest European fungal

cul-ture collections (released in

Janu-ary 2004);

•

the “CABRI” project (Common

Access to Biological Resources

and Information) establishes and

maintains standards and

guide-lines for culture collections for the

recognition of European Biological

Resource Centres. It is an initiative

of a consortium of European

cul-ture collections including CBS, the

Deutsche Sammlung von

Mikroor-ganismen und Zellkulturen, the

Belgian Co-ordinated Collections

of Microorganisms, Institut Pasteur

and Interlab Cell Line Collection.

•

three EU projects, including (a)

European Biological Resources

Centres Network (EBCRN), for the

establishment of a framework to

maximize complementarities and

minimize duplications among

European biological resource

cen-tres (BRCs), (b) EuroCat

(Euro-pean Catalogue of Life), a Species

2000 project, and (c) the

“Micro-Organisms Sustainable use and

Access regulation International

Code of Conduct” (MOSAICC), a

project aimed at implementation of

the international Convention on

Biological Diversity (CBD) that was

adopted by world leaders at the

1992 Earth Summit in Rio de

Ja-neiro.

CBS also cooperates in the

OECD working party on

biotech-nology’s task force on Biological

Resources Centres.

In addition to distributing

strains (more than 5000 strains in

2003), we also counsel industrial

and academic partners,

participat-ing in courses and developparticipat-ing joint

research programme s with the

industry. For example we

screened, in collaboration with a

drug discovery company (Kiadis,

The Netherlands) a large number

of strains for the production of

sec-ondary metabolites.

Bioinformatics and databasing

The first computerized CBS List of

Cultures appeared in 1978. From

1986 on CBS started recording

data directly in databases, and

now our on-line databases are

be-ing searched thousands of times

each week. CBS is developing

itself further as a ‘web based

ex-pertise centre’.

Developments are going on in

three fields, as outlined below.

On-line publications

. CBS is

pre-paring to bring the full text of its

scientific publications on-line. This

will start with the journal Studies in

Mycology, but other publications,

e.g. volumes in the CBS

Biodiver-sity Series, will follow.

Nomenclature and basic data

. CBS

researchers have published

mono-graphs on many groups of fungi.

Projects have been started to

con-vert the texts of these monographs

into a format that can be loaded

into the collection database and

integrated with the data that are

already available. In 2003, this

procedure was carried out for the

Aphyllophorales. About 30

000

names in this group are now part

of the CBS collection database,

which holds about 70 000 names.

On the web, the Aphyllophorales

database still appears as a

sepa-rate database, because in this

group the data are more complete

than in other groups. Other groups,

however are waiting in the wings,

e.g.

Cercospora

,

Mycosphaerella

,

Penicillium

,

Aspergillus

,

Phyllos-ticta

, and

Lactarius.

Lists of names

published before 1833, including

sanctioning by early mycologists

E.M. Fries and C. H. Persoon, will

also be posted.

In collaboration with CABI

Bio-science these names will be

merged with the 350 000 fungal

names currently available through

the “Index Fungorum”, and made

available on the Internet. The

number of names will be further

increased by scanning and

digitiz-ing lists of names that have never

been digitized so far.

In 2003, CBS also made an

Anamorph-Teleomorph database

available online; this database was

previously hosted by the University

of Alberta, Edmonton, Canada.

Users can search the database

and propose additions or

im-provements, which are only

ac-cepted when they have been

ap-proved by a CBS scientist.

My-cologists who want to contribute

can obtain a username and a

password to log in into the

data-base through the Internet; their

modifications are available to

eve-ryone immediately.

Also in 2003, information from

all type specimens in the CBS

her-barium was added to the

data-base. Plans to digitize the

herbar-ium depend on the availability of

funds for data entry.

Research data.

In order to make

our collections ever more useful

and to share the important

infor-mation that we gathered in our

research, we have co-developed

(in association with BioAware SA)

a new version of the Web

BioloM-ICS data handling software as well

as a new database dedicated to

yeasts. Detailed information about

more than 850 yeast species and

5500 yeast strains is now available

online. Hundreds of characters are

now annotated for each record; the

characters listed include

morpho-logical, and physiological

charac-ters as well as sequence and other

molecular characters. This

infor-mation is freely accessible for each

record, as is much additional textual,

biblio-graphic, geographic and taxonomic information.

The database includes thousands of macro- and

microscopic images and a bibliography of almost

10 000 references. The taxonomic database

fea-tures 23 500 scientific names (including

ana-morph and teleoana-morph names as well as

syno-nyms). It is also possible for users to align their

own sequences with a database containing up to

450 000 fungal sequences. New features in the

BioloMICS software now allow polyphasic

similar-ity-based identifications (meaning “identifications

at strain or species level”) that can be performed

using any combination of morphological,

physio-logical, sequences or molecular data. In 2004, the

fungal and bacterial databases will also be made

available on the Internet and will feature a

simi-larly rich array of morphological, physiological,

molecular, nomenclatural, bibliographic and

geo-graphic data.

The future

For the future, culture collections like the CBS will play

key roles in many research programme s involving a

wide range of topics such as phylogeny and evolution,

ecology and biodiversity, functional genomics,

bioin-formatics and metabolomics. Biotechnological

devel-opments related to the interests and needs of the

in-dustrial world will remain at the core of our research

programme s, and fruitful collaborations will be

pro-moted. Our aim is to constantly improve our processes,

as well as the quantity, quality and the diversity of our

strains. For these strains, an increasing amount of

scientifically and industrially relevant data will be

re-corded in multi-factorial databases managed by

ad-vanced polyphasic analysis software.

Ecology and biodiversity are tightly linked together, and both are among the most urgent matters of our modern age.

Climate change threatens to submerge some nations and extinguish species and habitats, but are these processes

truly taking place? Fungal indicator organisms such as climate-sensitive lichens, heat-loving human pathogens and

ecologically specialized symbionts can let us know – but first we have to be able to recognize them properly.

Wastes and pollutants are thrown, blown and poured onto the land: will they be broken down by microorganisms,

and if they are, will they be rendered harmless or toxic? Studies of decomposer fungi will tell us the answer – but we

need to know which decomposer is doing what. Obscure microorganisms growing on tropical leaves and in many

other habitats on our biodiverse planet may make undiscovered compounds that could cure diseases and begin new

industries – but someone must find them and characterize them before their potential can be unlocked. Just as no

books can be written before there is an alphabet, no ecology can be done without a biosystematics that can reliably

identify and genetically characterize organisms. Furthermore, just as keeping written information available requires

a library or database, keeping microbial ecological information alive requires well-curated culture collections and

herbaria.

Control of fungi in soils

Crop plants growing in the field and trees growing in forests and

planta-tions are susceptible to many pathogens. In agriculture, an

ozone-destroying chemical called methyl bromide has often been used to

elimi-nate soil-borne disease organisms. Concerns about global warming have

meant that it will soon no longer be possible to do this. Is a purely natural

control possible? We know that some natural soils have few pathogenic

fungi, whereas others contain large numbers of harmful organisms. One

factor that can eliminate harmful fungi from soils is fungus-killing bacteria.

CBS is involved in collaboration with the Netherlands Ecological Institute

(NIOO) to study the distribution of bacterially and fungally dominated soil

types in the Netherlands, and the characteristic fungal and bacterial

popu-lations they support. Fungus-destroying bacteria are being studied to

determine how they attack fungi, which fungi are attacked and not

at-tacked, and what happens in bacterial and fungal gene expression when

these confrontations are occurring. Members of a newly recognized, but

relatively common, bacterial group in Netherlands soils are able to pierce

fungal cell walls directly by producing enzymes degrading chitin, the

pre-eminent chemical component of these walls. Comparative genomics

techniques are being utilized to determine if fungi have any inducible

de-fenses – that is to say, the equivalent of an immune system – that

re-sponds to these bacterial attacks.

Bioindicators of global warming

Fungi growing out in the open on stones and twigs are especially likely to

experience effects due to climate changes and changes in air quality. It

has been known for many years that lichens are particularly sensitive, and

they are often used as indicator organisms of temperature trends and

pol-Dictyochaeta

species (strain CBS

111766), a spectacular mould from a

rotting leaf in Brazil.

lutant levels. This knowledge,

com-bined with the fascination these often

beautiful organisms inspire in many

professional and amateur lichen

en-thusiasts, has given rise to a

long-term project to monitor lichen

popula-tions in multiple locapopula-tions across the

Netherlands. From these data and

from voucher collections in herbaria,

it can be seen that certain lichens,

such as

Bacidia

species, that are

apparently associated with warmer

climate areas are in the increase in

the Netherlands, while others more

associated with cold climates are on

the decrease. These studies have

stimulated nation-wide radio and

television, and newspaper coverage.

The accuracy of the survey was

greatly enhanced by recent

system-atic work done on the lichens

them-selves. The study of lichens is

cou-pled with the study of so-called

lichenicolous fungi, culturable fungi

that grow in lichen thalli (vegetative

bodies) and sometimes parasitize

the lichens. These fungi may be rich

sources of unusual enzymes and

metabolites because of their growth

in the biochemically unusual

envi-ronment of the lichen thalli, which are

often densely loaded with

antimicro-bial and toxic compounds produced

by the lichens.

Healthy plants are partly made of

fungus (endophyte studies)

The bodily tissues of humans and

animals are normally free of fungi,

but this is not true of plants.

Senescent oak leaves showing leaf spots

caused by a variety of fungi.

Even when perfectly healthy, plants

tend to have specialized fungi

grow-ing within them as so-called

endo-phytes (plant-interior dwellers).

Our research has shown that fungi

involved in the decay of fallen oak

leaves in the autumn often “get the

jump on the competition” by

colo-nizing those same leaves as

harm-less endophytes much earlier in

the year.

This early, quiet “real estate

speculation” on the part of

My-cosphaerella

species and other

oak leaf occupiers then leads to

rapid, fullscale colonization and

reproduction as soon as the leaf is

shed from the tree. Few

competi-tors are able to gain access to the

leaves until the former endophytes

have finished digesting and

repro-ducing. Most cases where

endo-phyte relations have been looked

at in detail have disclosed that the

plant gains some advantage from

the relationship. What this might

be with oak leaf endophytes is as

yet unknown, but many other

known fungal endophytes protect

plants against diseases by causing

them to arm their defense

(immu-nity) mechanisms, or protect them

against grazing insects or animals

by producing unpleasant flavour

compounds. Many of the

endo-phytic fungi are of strong

biosys-tematic interest, and in particular,

oak leaves typically support

My-cosphaerella punctiformis

, the

‘type species’ of the large and

economically important genus

My-cosphaerella

. The systematic

un-derstanding and correct naming of

many crop pathogens and

patho-gens of wild plants depends on

correct understanding of this ‘type’

or standard-bearing species that

defines how the name

Mycosphae-rella

can be logically and

scientifi-cally applied.

Collecting oak leaves in the Netherlands to study colonization of healthy leaf tissues

by endophytic fungi

Array of fungi growing out from where a

surface-disinfected oak leaf was impressed

on fungal growth medium.

Wine with a bouquet of fine research

(yeast systematics)

A successful wine brand that was

re-leased on the North American market

in the 1990’s was called

Rotting Grape

.

In away, that deliberately anti-classical

title describes all wine. If the beauty of

the fungal kingdom isn’t enough to

convince some people that rot can be

noble, then perhaps drinking a fine

wine will do the trick. But there is rot

and then there is rot. Recent CBS

studies have involved the

biosystemat--2.0

5.0

0.

0

3.

5

Humidity

pH

Organic

Matter

Salinity

Bacterial

biomass

Fungal

biomass

Si

lt

M

a

rra

m

m

a

rs

h

S

a

n

d

dune

s

R

e

e

d

m

a

rs

h

Sc

ru

b

Gr

a

s

s

la

n

d

Y

o

u

ng pi

ne

f

o

re

s

t

Y

oung oa

k

f

o

re

s

t

O

ld pi

n

e

f

o

re

s

t

O

ld oa

k

fo

re

s

t

(a)

(b)

(c)

Ma

tu

ri

ty

-2.0

5.0

0.

0

3.

5

Humidity

pH

Organic

Matter

Salinity

Bacterial

biomass

Fungal

biomass

-2.0

5.0

0.

0

3.

5

Humidity

pH

Organic

Matter

Salinity

Bacterial

biomass

Fungal

biomass

Si

lt

M

a

rra

m

m

a

rs

h

S

a

n

d

dune

s

R

e

e

d

m

a

rs

h

Sc

ru

b

Gr

a

s

s

la

n

d

Y

o

u

ng pi

ne

f

o

re

s

t

Y

oung oa

k

f

o

re

s

t

O

ld pi

n

e

f

o

re

s

t

O

ld oa

k

fo

re

s

t

(a)

(b)

(c)

Ma

tu

ri

ty

Molecular diversity of soil fungal populations in dune environments of different maturity in The Netherlands: (a) Detrended Canonical Correspon-dence Analysis (DCCA) diplot showing degrees of relatedness among fungal sampling sites (small circles, three replicate samples per sampling site) and the distribution of samples along environmental gradients (red arrows); (b) Example of a denaturing gradient gel electrophoresis (DGGE) pattern used in the DCCA. DNA bands in the pattern indicate individual species obtained from soil DNA extracts subjected to amplification with fungal-specific primers targeting the ribosomal small subunit DNA; (c) Schematic representation of the transect.

ics of yeasts that were once thought

to be spoilage organisms in the

wine-making process, but are now

under-stood to contribute subtle and

desir-able flavours when their growth is

properly handled. These yeasts, in

the genus

Hanseniaspora,

tend to

grow along with the main wine

fer-mentation yeast,

Saccharomyces

cerevisiae

. There are several

promi-nent

Hanseniaspora

species and

each may have its own effect on

fla-vours. Knowing the biosystematics

of these yeasts is the key to getting

the right strains involved in

wine-making. Thus, this research is an

excellent step in the direction of

producing the perfect wine.

Indoor fungi play an important role in our daily life, both as contaminants on food and feed (spoilage, fermentation)

and as agents of deterioration in building materials and in valuable stored materials such as artworks and other

mu-seum objects as well as archives. Worldwide, the quantity of food products that is lost due to fungal spoilage is

im-mense. This loss can be caused by post-harvest problems, where fungi attack still-living fruits, vegetables and

grains, but can also arise when processed foods are affected by spoilage fungi. The growth of fungi may result in

off-flavours, altered structure, and discolouration, which all contribute to the conspicuous phenomenon of rot. What is

not so readily visible but is much more alarming is the formation in some contaminated foods of fungal toxins or

pathogenic or allergenic fungal propagules. Over the past 40 years, fungi in foods have received special attention

because of their ability to produce toxic metabolites, the so-called mycotoxins. In addition to concerns about

my-cotoxins in foods, there is also currently increasing concern over the fungal growth within buildings. Although fungi

are always present around us and cannot be eradicated totally, some aspects of their excessive presence in

build-ings can be linked to serious adverse health problems.

Food mycology

Currently, there is a strong demand for fresh food products preferably

containing no added preservative substances. This quest for healthy

foods paradoxically tends to stimulate a novel upsurge in fungal spoilage

incidents. In general, several strategies for food preparation can make it

difficult for fungi to cause contamination. Long-standing techniques

in-clude controlling inin-clude water activity through drying or by adding salt or

sugar, using pasteurization, canning or other types of heat treatment, and

using storage conditions unfavourable to fungi, such as low temperatures

or acidic materials such as vinegar. Some fungi, however, are resistant to

these traditional preservation methods. To fight these specialized food

spoilage fungi, food preservatives are added, but even with these

materi-als, resistant fungi may occur. In connection with these problems,

re-search has been initiated at CBS to evaluate possible new food

preserva-tives and to determine their influence on fungal cells.

At CBS, the fungus

Talaromyces macrosporus

is used as a model

sys-tem to study the biology of heat resistant ascospores in detail. These

spores allow the fungus to survive heat treatment of foods; indeed, they

often remain dormant until they are stimulated to germinate by high

tem-peratures. Various molecular and microscopical tools are used to unravel

the mechanisms that cause the extraordinary stress resistance of the

as-cospores. An additional aim of the studies is to characterise the

phe-nomenon of activation of spores by heat or other stress factors. The

na-ture of dormancy, activation and germination of heat-resistant ascospores

has been an enigma for more than 30 years now and it is now being

ad-dressed in a multi-disciplinary way.

Mycotoxins

More than 400 mycotoxins are known today, of which the potently

car-cinogenic aflatoxins are the best known. The number of mycotoxins

known to science is increasing rapidly. Mycotoxins are so-called

secon-dary metabolites, produced mainly in mature rather than young fungal

colonies, which are toxic to vertebrate animals even when introduced via

a natural route. Different mycotoxins affect different cellular processes

and have distinct systemic or site-specific medical effects. These include

Heat activation 0.00 0.20 0.40 0.60 0.80 1.00 1.20 0 50 100 150 Time (sec) Viable Cou nt (of max im um)

Very short heat treatments of dormant as-cospores at 85 °C are able to activate the spores to germination within 1 min (Top Panel). One stage of germination is a very quick bursting of the thinly walled inner cell through the very thick, ornamented outer cell wall of the spore (Bottom panel).

suppression of the immune system

and the causation of DNA damage

leading to the development of

can-cer. Only a few mycotoxins have

been well described in terms of

their toxicological effects.

Thin Layer Chromatogram showing the secondary metabolites of Penicilliumstrains isolated from food.

The presence on food products

of fungi potentially producing

my-cotoxins does not always mean

that these products actually

con-tain mycotoxins. Various

environ-mental factors play a role in

whether or not the fungi will form

these secondary metabolites. The

toxic properties of many frequently

occurring moulds have not yet

been fully investigated and

chemi-cal tests for rapid identification or

detection of specific mycotoxins

are scarce. To assess the risk

posed by food contaminated by

fungi, it is important to correctly

identify the contaminating species,

since this will usually be the

quick-est way to determine which toxins

may have been formed.

The taxonomy of the

mycotoxin-producing genera

Penicillium

and

Aspergillus

has been investigated for

many decades and constitutes one

of the central themes of the CBS,

which has been doing taxonomic

research on these genera since the

1940’s. The taxonomic research of

today is based on a strong

interdisci-plinary and integrated approach

in-cluding study of morphology,

bio-chemistry, physiology and molecular

biology.

Fungi in indoor environments

Construction materials can be

de-graded, paper materials such as

wallpaper can be attacked and, when

present in high quantities, fungi can

pose a health risk through their

pro-duction of toxic or irritating volatiles

or due to the presence on their

propagules of chemicals stimulating

allergic sensitization in persons with

a predisposition towards allergies.

Persons with asthma and other

respiratory conditions are

espe-cially at risk. Fungal proliferation

indoors is often related to

leak-age, flooding, condensation and

excess humidity. Lack of

ventila-tion may exacerbate these

prob-lems. Occupants may also

con-tribute to mould growth by doing

things that generate high

humid-ity levels, or by obstructing

vent-ing of the buildvent-ing. Problems

oc-cur in both old and new

build-ings, and often arise after inferior

renovation work has been done,

or after tight insulation has been

installed. Nowadays, many

prob-lems occur worldwide with the

large scale air-handling systems

(called “heating, ventilation and

air conditioning” [HVAC]

sys-tems) used in large, modern

buildings. Appropriate

mainte-Peanuts contaminated with Eurotium herbariorum.

An Aspergillus niger isolate producing the mycotoxins ochratoxin A, B, α and β, detected by high pressure liquid chromatography with fluorescent detection, HPLC-FLD (lower trace, excitation [ex] 230 nm, emission [em] 450 nm).

nance of such systems is

impor-tant to prevent fungal growth.

The main objectives for the

in-vestigation of fungi in indoor

envi-ronments are to detect the source

of excess moisture causing fungal

growth, to measure the fungal load

present indoors, and to quantify

the exposure of building occupants

to fungi and their potentially toxic,

irritating, or allergenic metabolites

and cell wall components. Contrary

to what occurs with other research

topics in mycology, the

methodol-ogy and interpretation of the

re-sults used in different countries

and even different laboratories

may differ considerably. This often

makes direct comparison of results

impossible. There is an urgent

need to establish universal

guide-lines. From the medical as well as

from the building construction

standpoint, the need to establish

protocols for sampling and

inter-pretation of the results is strongly

felt. The ultimate goal is to achieve

full standardization. CBS

re-searchers are promoting this

proc-ess by collaborating in the setup of

Fungal contamination behind a sofa in a Dutch house.

Interlaboratory tests showing that the mycological knowledge of 58 laboratories supplying services for fungal indoor problems is unsatisfactorily.

Fungi detected in a sample of house dust.

interlaboratory studies in which a

standard set of common indoor

fungal cultures are dispatched to

various testing labs in order to

en-sure good quality identifications

are made at each one. In this

pro-ject, CBS is collaborating with

German research groups in

Stutt-gart and Lübeck. Guidelines for

detecting, identifying and handling

indoor fungi have been published

in cooperation with the

Landesge-sundheitsamt, Baden-Württemberg

in Germany.

With the increasing global human population, the importance of producing food sufficient in quality and quantity

re-mains imperative for sustaining quality of life. Each year millions are lost in revenue due to plant disease caused by

various phytopathogenic fungi. To combat these diseases on an international scale, it is important to clarify whether

it is the same species and genotypes that occur in various countries, since each different species and genotype can

be expected to have different patterns of attack, fungicide and climatological responses, and so on. With such

pathogens, it is also important to know what their host ranges and mating strategies are, and how this relates to

dif-ferent disease control mechanisms. For example, organisms that mate frequently can be predicted to be more

ge-netically variable and hence more adaptable than those that do not. Knowing which organisms occur where and on

what crops also facilitates free trade in agricultural produce while at the same time diminishing the risk of pathogen

introduction. In this programme, we address these economically vital matters by investigating the speciation and

host adaptation of various important phytopathogenic fungi.

Evolutionary Phytopathology

Evolutionary Phytopathology

5062 5072 5119 5123 EcoRV: GAT/ATC

50

62

50

72

51

19

51

23

5062 5072 5119 5123 From left to right : Cercospora leaf spot symptoms on a plant; a SEM photo of Cercospora conidia erupting from a stoma; Sequence align-ment showing a polymorphism that can be cut by the enzyme EcoRV in sample 5062; DNA fragments on a gel after cutting with the enzyme - sample 5062 has the polymorphism and is cut by the enzyme and the others are not; A tree showing the relationship between the samples as derived from the sequence data.

Host specificity and

speci-ation in

Mycosphaerella

The genus

Mycosphaerella

represents one of the largest

genera of ascomycetous fungi.

The thousands of species

in-cluded in this genus have been

linked to diseases on most

gen-era of flowering plants. In the

past it has always been

as-sumed that these fungi are

highly host-specific, and that

different plant hosts harbour

different fungal species. Since

the implementation of

molecu-lar phylogeny as the basis of

modern taxonomy this

‘mo-nogamous’ relation between

plant and fungal species has

become more and more

debat-able. As very few of these

or-ganisms have been cultured to

date, the issue of host

specific-ity remains largely unanswered.

A major aim of our research is

to determine how exclusive the

host-pathogen relationship of

Mycosphaerella

species is.

Investigations based on

ge-nomic analysis are in progress

on fungal species from a wide

range of plant hosts. Most

sexual fungal genera like

My-cosphaerella

have asexual

re-productive states that may

ap-pear separately and may even

branch off to give rise to

com-pletely asexual species. Such

asexual forms were often

diffi-cult to trace to a sexual

ances-tor and were thus hisances-torically

put into separate genera. The

genus

Cercospora

represents

one of the corresponding

asex-ual genera of

Mycosphaerella

.

Presently it has more than 659

recognized species, of which

281, when grown in culture, are

morphologically

indistinguish-able from a species that is

pro-totypically a celery pathogen,

Cercospora apii.

These

spe-cies have been collectively

re-ferred to as the

C. apii sensu

lato

(=

C. apii

“in the broad

sense”) species complex. To

address the issue of whether

M. colombiensis 10548 M. colombiensis 10547 M. colombiensis 10549 4303 Poa 0000 Ali 5441 Ama 1052 Sal 10079 Cam 113127 Pon 10124 Phy 1051 Sal 5055 Poa 4410 Rut 4411 Rut 10122 Ast 5128 Che 5113 Plu 5370 Che 5072 Che 5074 Che 5069 Che 5070 Che 5065 Mal 5369 Che 5062 Che 5071 Che 10171 Che 5064 Che 5123 Api 5125 Che 5260 Ast 5111 Lam 5087 Api 5073 Che 5057 Cis 5119 Che 5083 Plu 5086 Api 5063 Che 5112 Lam 5084 Pla 5110 Lam 3955 Fab 5261 Bra 10100 Bra 5088 Bra 10133 Bra 5359 Bra 5366 Ona 5060 Bra 5061 Bra 5082 Fab 5056 Bra 5090 Bra 5439 Pol 3958 Fab 3957 Fab 5078 Fab 5367 Fab 5079 Vio 5368 Vio 5473 Big 5089 Fab 5091 Fab 5114 Ast 5437 Fab 5118 Fab 5066 Mal 5117 Mal 10104 Eup 10455 Ast 10627 Ast 10628 Ast 10629 Ast 10082 Ast 10094 Con 5075 Sol 5076 Sol 10102 Pol 10109 Lil 10117 Pol 10128 Urt 10553 Fab 113131 Pon 113125 Pon 113123 Pon 113124 Pon 113126 Pon 113130 Pon 113128 Pon 113129 Pon 10552 Rut 10526 Fab 10527 Fab 5262 Mal 3947 Rut 3945 Rut 3946 Rut 3950 Rut 3948 Rut 3949 Rut 4001 Rut 5328 Fab 5326 Fab 5327 Fab 4002 Rut 10551 Fab 10550 Fab 5332 Fab 5329 Fab 5325 Fab 5333 Fab 5330 Fab 5331 Fab 5067 Fab 5068 Fab 5259 Ros 5126 Ona 5127 Ona 1137 Fab 1138 Fab 4408 Rut 4409 Rut 5059 Fab 5085 Ari 5360 Ast 5440 Sol 10138 Lam 5363 Hyd 10615 Ast 5365 Ona 10616 Ast 5364 Hyd 5362 Hyd 5116 Con 5438 Lam 10091 Ama 1134 Fab 10266 Api 10265 Api 10267 Api 5115 Mal 5361 Bra

Neighbor joining tree of a combined ITS, actin, calmodulin and elongation factor 1-alpha sequence alignment. The phyloge-netic relationship between different

My-cosphaerella isolates (four digit number identifies the isolate and the three letter name the host family) occurring on different host plants is shown.

these different taxa represent

clones from different populations

or true separate species, a major

international isolate collection

has been assembled and

ana-lysed with by sequencing

multi-ple DNA loci (i.e., gene regions).

Cercospora beticola

, an

impor-tant pathogen of sugar beet in

Europe and a recognized

mem-ber of the

C. apii s. lat

. complex,

has been used as a pilot project.

We are currently involved in

es-tablishing what degree of

varia-tion occurs in populavaria-tions of this

species, allowing us to refine our

methods so that we can

ulti-mately extend our analysis to the

whole phylogenetically related

group falling within

C. apii ss. lat

.

A DNA phylogeny approach

has also been used to gain an

understanding of the evolution

and inter-relationship of

My-cosphaerella

species causing

defoliation of

Eucalyptus

tree

species that are cultivated for the

paper and pulp industry.

Re-cently, a similar project has been

initiated to study

Mycosphaerella

species causing defoliation of

bananas. Although several

spe-cies of

Mycosphaerella

have

been reported from banana,

four are relatively common, and

are regarded as the most

dam-aging species, namely

M.

mu-sicola

, the causal agent of the

dreaded and rapidly spreading

Sigatoka disease,

M. fijiensis

,

the causal agent of the global

forerunner of Sigatoka, black

leaf streak disease,

M. musae

and

M. eumusae

. Multi-locus

DNA sequencing has revealed

several additional, as yet

unde-scribed species of

Mycosphae-rella

that occur on banana

plants. The possibility of

inter-action and hybridization among

these species is being

investi-gated.

Also, the mating type genes

of

M. fijiensis

,

M. musicola

and

M. eumusae

are being cloned,

and their distribution within

populations is being

deter-mined. This is being done to

assess the occurrence of

sex-ual reproduction, a factor

con-trolling genetic recombination

and genotypic diversity, and

thus the risk of new disease

epidemics.

Hybridisation in

Phyto-phthora

and

Pythium

Pythium

and

Phytophthora

are

two highly economically

signifi-cant genera of fungus-like

Oo-mycetes responsible for many

types of crop disease and tree

decline; the best known of the

crop diseases is potato blight

(

Phytophthora infestans

), the

cause of the Irish potato famine

and a major agent of crop

damage to this day. A

molecu-lar phylogeny study spanning

all available biodiversity within

Black leaf streak diseases of banana, caused by

Mycosphaerella fijiensis.

LEGEND Ali = Alismataceae Ama = Amaranthaceae Api = Apiaceae Ari = Aristolochiaceae Ast = Asteraceae Big = Bignoniaceae Bra = Brassicaceae Cam = Campanulaceae Che = Chenopodiaceae Cis = Cistaceae Con = Convolvulaceae Eup = Euphorbiaceae Fab = Fabaceae Hyd = Hydrangeaceae Lam = Lamiaceae Lil = Liliaceae Mal = Malvaceae Ona = Onagraceae Phy = Phytolaccaceae Pip = Piperaceae Pla = Plantaginaceae Plu = Plumbaginaceae Poa = Poaceae Pol = Polygonaceae Pon = Pontederiaceae Ros = Rosaceae Rut = Rutaceae Sal = Salicaceae Scr = Scrophulariaceae Sol = Solanaceae Urt = Urticaceae Vio = Violaceae

the genus

Pythium

has been

completed by CBS researchers

in collaboration with

interna-tional colleagues. In a more

specific study, a group of 28

isolates of the mammalian

pathogen

Pythium insidiosum

,

the only

Pythium

group known

to cause human disease, were

subjected to analysis of their

ribosomal internal transcribed

spacer (ITS) gene region,

re-vealing different, geographically

correlated clusters. Specific

DNA probes were developed

for the purposes of medical

di-agnosis.

Phytophthora

, a genus

comprising many highly

de-structive plant pathogens, is

being taxonomically revised

now that molecular techniques

have disclosed much new

in-formation about its constituent

species. The ribosomal ITS

region of more than 500 strains,

representing all currently

avail-able species of this genus, is

being analyzed. Isolates of the

recently described

Phy-tophthora ramorum

, the agent

of the newly recognized

dis-ease “sudden oak death,” were

obtained from different origins

in Europe and the USA. A

comparative study showed that

US isolates were more variable

than European isolates in

mor-phology and growth rate.

Real-time PCR, a DNA amplification

technique including the ability

to monitor levels of DNA

pre-sent at each cycle of the

ampli-fication chain reaction, was

used in the development of a

test designed to specifically

detect

P. ramorum

and to

dis-tinguish its European and

American genotypes.

Part of the

Phytophthora

project is a study of isolates

that could not be assigned to

any of the known species. The

morphology of these unusual

isolates either deviated from

that of known species, or it

suggested an intermediate,

hy-brid origin. Analysis of isozyme

proteins and ITS sequences

confirmed that some isolates

are indeed likely to be hybrids.

Other isolates proved to be

‘outliers’ genetically similar but

not identical to known species,

while in some cases, the

iso-lates studies appeared to

rep-resent entirely new species. In

two cases, both involving

sev-eral isolates, the hybrid nature

of the isolates could be

demon-strated by doing additional

mo-lecular studies typically done to

show hybridization. In one of

these cases, all the hybrid

strains were isolated from plant

hosts differing from those

sup-porting the parent species, both

highly specific to particular

plant hosts. This suggests that

the hybrids’ mixture of genetic

properties allows them to affect

plants other than the hosts

supporting their parents. This

finding may be of high

eco-nomic relevance since it may

reveal a major pathway by

which new diseases evolve to

attack valuable crops, a

phe-nomenon that occurs at an

un-predictable rate within a time

scale ranging from years to

decades.

Symptoms of

Phytophthora

root rot on grapevines.

The recent outbreaks caused by the SARS and bird influenza viruses have made the public well aware of the

exis-tence of environmental pathogens. The fact that a number of fungi are also important environmental pathogens is

less well known. These fungi are all able to cause severe infections in humans, even though their natural habitat lies

elsewhere. The virulence factors that give rise to the pathogenic potential of these organisms are derived from

adap-tation to the natural ecological niche. Understanding how these organisms developed virulence to humans, then,

requires overall knowledge of their ecology and evolution.

some way connected with

extre-motolerance, we conducted

in-depth studies into a number of

re-markably extremotolerant fungi

isolated from harsh environments.

These fungi, for the major part,

were unknown to science and still

have to be described as new

gen-era and species. As an example,

we obtained rock-colonizing fungi

in Antarctic ice-free deserts.

Such fungi grow at the outermost

edge of the conditions potentially

supporting life, surviving average

temperatures of -40°C, and

grow-ing almost without water and

nutri-ents while being subjected to high

levels of UV radiation. Their growth

rate is extremely slow, and they

grow only as very small

microcolo-nies. Such organisms could well be

studied as models for

extra-terrestrial life and are therefore

used in modelling the possible

forms of life on other planets, such

as Mars. Other microcolonial fungi

are known to degrade

sun-exposed marble in the

Mediterra-nean, growing under extreme

con-ditions of drought and at

tempera-tures up to +60°C. One common

factor that characterizes all these

microcolonial fungi, which are very

diverse in terms of phylogenetic or

evolutionary origin, is the

devel-opment of clump-like

“meris-tematic” growth.

Antarctic expedition of Imre Friedmann and coworkers analysing biological weathering on the rock formation "Battleship Promontory".

used to advocate this idea is

refer-ence to a severely

immunocom-promised patient, vulnerable to

being infected by a wide variety of

household fungi, as a 'living petri

dish', i.e., a supermarket for

mi-crobes. A term used to describe

fungi generally able to survive

ex-treme conditions is

“extremotoler-ant.” To test the hypothesis that

medically important fungi are in

Several hypotheses have been

put forward to explain how

cer-tain fungi became pathogenic to

humans. The most common idea

– and from our point of view the

least probable one – is that

these fungi simply have a broad

tolerance of adverse conditions,

and thus are able to survive

when accidentally inoculated into

humans. A popular catch-phrase