chapter6 part 1.ppt

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Chapter 6

Chapter 6

Marine Microbes

Key Concepts

• Microbial life in the sea is extremely

diverse, including members of all three

domains of life as well as viruses.

• Marine virology is an emerging field of

Three domains of living organisms

AKA Eubacteria AKA Extremophiles _{“Have nuts”}

Key Concepts

• Photosynthetic and chemosynthetic

bacteria and archaeons are important

primary producers in marine ecosystems.

• Heterotrophic bacteria, archaeons, and

Key Concepts

• Marine eukaryotic microbes are primary

producers, decomposers, and consumers,

and some contribute significantly to the

accumulation of deep-sea sediments.

• Populations of several kinds of

photosynthetic marine microbes may form

harmful blooms that affect other marine

Marine Viruses p. 96nbcn

• Virology—the study of viruses

• Viruses are diverse and are more abundant

than any other organism in the sea

• Have significance for marine food webs,

population biology and diseases of marine

organisms

• Viruses of marine eukaryotic hosts first

reported in the 1970s

I. Viral Characteristics

• NOT ALIVE

• Consist of bits of DNA or RNA surrounded by protein

• no metabolism

– rely on host organism for energy

I. Viral Characteristics

• must reproduce in a host cell

• Origin of viruses: two hypotheses

1. highly reduced prokaryotic parasites 2. renegade genes • Infect all living

Viral Characteristics

• Viral structure

– virus particle is called a virion when outside the host cell

– virion composed of a nucleic acid core surrounded by a coat of protein called a capsid (together called a nucleocapsid)

– may have a protective envelope, a membrane derived from the host’s nuclear or cell

Viral Characteristics

• Viral structure (con’t)

– viral shapes:

• icosahedral viruses—capsid with 20 triangular faces composed of protein subunits

• helical viruses—protein subunits of the capsid spiral around the central core of nucleic acid

• binal viruses—those with icosahedral heads and helical tails

Viral Characteristics

• Viral life cycles

– lytic cycle—a rapid cycle of infection,

replication of viral nucleic acids and proteins, assembly of virions, and release of virions by lysis (rupture) of the cell

– lysogenic cycle—nucleic acid (DNA or RNA) is inserted into the host genome and may

reside there through multiple cell divisions

Viral Life Cycle p.95nb Virus reproduces in 2 ways: 1.lytic cycle

2.lysogenic cycle

1

Biodiversity and Distribution

of Marine Viruses

• 10 times more abundant than marine

prokaryotes

, may reach 10

virons per liter

of seawater, 10

per kilogram of sediment

• Estimated 100 to 10,000 genotypes

• Most planktonic viruses are icosahdral or

binal bacteriophages (“bacteria eaters”) with

lytic life cycles

II. Ecology of Marine Viruses

• Kill host cells, and thus control populations of bacteria and other microbes in plankton

communities

• Responsible for chronic infection and mass mortality of marine animals

• Bacterial lysis can alter biogeochemical cycles and planktonic food webs

• Viral populations are probably controlled by several biotic and abiotic factors

Marine Bacteria

I. General characteristics

– simple, prokaryotic organization: no nuclei or membrane-bound organelles

– reproduce asexually by binary fission – many shapes and sizes

• bacillus – rod shape

• coccus – spherical shape

– Diplo – two of them

– Strepto – a chain of them

– Spaphlo – a bunch (glob) of them

Marine Bacteria

I. General

characteristics – simple,

prokaryotic – no nuclei or

membrane-bound

organelles – Circular DNA

Cell division in prokaryotes

egg ASEXUAL REPRODUCTION

SEXUAL REPRODUCTION Sperm

Fertilized egg

Stepped Art

Carbon dioxide Oxygen Aerobic respiration Aerobic respiration PRIMARY PRODUCERS Photo-synthesizers Cyanobacteria Phytoplankton Multicellular algae Plants Chemo-synthetic bacteria Consumed by Consumed by CONSUMERS Zooplankton Animals Consumed by Nutrients released Nitrogen Sulfur Phosphorus Aerobic metabolism Fermentation Wastes Die Die Anaerobic bacteria DECOMPOSERS Aerobic bacteria and fungi Stepped Art

Most important marine bacteria

• Cyanobacteria (blue-green bacteria)

– photosynthetic bacteria which are found in environments high in dissolved oxygen, and produce free oxygen

– store excess photosynthetic products as starch and oils (become fossil fuel)

– primary photosynthetic pigments are chlorophyll

a and chlorophyll b

Most important marine bacteria

• Photosynthetic

• found in

environments high

in dissolved

oxygen (O

)

– They produce it!

Light energy

Sulfate (SO₄2–₎

Carbohydrates (CH₂O)_x (a) Cyanobacteria – Free oxygen produced

Carbon dioxide (CO₂)

Water (H₂O)

Hydrogen sulfide (H₂S)

Carbon dioxide (CO₂)

Light energy

(b) Purple and green bacteria – No free oxygen produced

Oxygen (O₂) Carbohydrates

(CH₂O)_x

Stepped Art

Cyanobacteria

• Cyanobacteria (continued) – chromatic adaptation—

response of pigment

composition to the quality of light in the sea

– may exist as single cells or

form dense mats held together by mucilage

• form associates called stromatolites—a coral-like mound of microbes that trap sediment and precipitate

Other Nutritional Types

• Other photosynthetic bacteria

– anaerobic green and purple sulfur and non-sulfur bacteria do not produce oxygen

– the primary photosynthetic pigments are bacteriochlorophylls

– sulfur bacteria are obligate anaerobes (they cannot tolerate oxygen)

– non-sulfur bacteria are facultative anaerobes

(respiring when in low oxygen or in the dark and photosynthesizing anaerobically when in the

Nutritional Types

• Chemosynthetic bacteria

– use energy derived from chemical reactions

that involve substances such as ammonium ion, sulfides and elemental sulfur, nitrites, hydrogen, and ferrous ion

– chemosynthesis is less efficient than

photosynthesis, so rates of cell growth and division are slower

– found around hydrothermal vents and some

shallower habitats where needed materials are

Nutritional Types

• Chemosynthetic bacteria

– use energy derived from chemical

reactions

Carbon dioxide (CO₂)

Hydrogen sulfide (H₂S)

Magma (molten rock)

Water (H₂O)

Carbohydrates

Produce

Elemental sulfur (S)

Carbon dioxide (CO₂) Animal

community

Carbon dioxide (CO₂)

Hydrogen sulfide (H₂S)

Chemosynthetic bacteria (in animal tissues, in water, and on rocks)

Stepped Art

Nutritional Types

• Heterotrophic bacteria

– decomposers that obtain energy and materials from organic matter in their surroundings

– return many chemicals to the marine environment through respiration and fermentation

– populate the surface of organic particles

Nutritional Types

• Heterotrophic

bacteria

– decomposers that obtain

energy and

materials from organic

Nitrogen Fixation and Nitrification

• Nitrogen fixation: process that converts

molecular nitrogen dissolved in seawater

to ammonium ion

– major process that adds new usable nitrogen to the sea

– only some cyanobacteria and a few

Nitrogen Fixation and Nitrification

• Nitrification: process of bacterial

conversion of ammonium (NH

) to nitrite

(NO

) and nitrate (NO

3-

) ions

– bacterial nitrification converts ammonium into a form of nitrogen usable by other primary

Nitrogen-fixing bacteria,

cyanobacteria

2 N +Hydrogen (H₂)

Ammonia (NH₃)

Dissolved nitrogen (N₂)

NITROGEN FIXATION Marine plants Microorganisms Phytoplankton Algae NITRIFICATION Animal wastes recycled by microorganisms

Ammonium (NH₄+₎

Bacteria +Oxygen (O₂) Nitrite (NO₂–₎

Nitrate (NO₃–₎

Ammonia (NH₃)

+Hydrogen (H₂)

Bacteria +Oxygen (O₂)

Stepped Art

III. Symbiotic Bacteria

• Many bacteria have evolved symbiotic relationships with marine organisms

• Endosymbiotic theory

– mitochondria, plastids & hydrogenosomes evolved as symbionts within other cells

• Chemosynthetic bacteria live within tube worms and clams

• Some deep-sea or nocturnal animals host helpful bioluminescent bacteria

– photophores

III. Symbiotic Bacteria

III. Symbiotic Bacteria

• Some deep-sea or nocturnal animals host helpful

bioluminescent bacteria

– photophores

Archaea p.

I. General characteristics

– small (0.1 to 15 micrometers) – prokaryotic

– adapted to extreme environmental conditions: high and low temperatures, high salinities, low pH, and high pressure

– formerly considered bacteria – differences from bacteria

• cell walls lack special glycoprotein (sugar-amino acid) compounds in bacterial cell walls

B. Nutritional Types

– archaea includes photosynthesizers, chemosynthesizers and heterotrophs

– most are methanogens: anaerobic organisms that metabolize organic matter for energy,

producing methane as a waste product

– halobacteria (photosynthetic), thrive at high salinities, trap light using bacteriorhodopsins, purple proteins

C. Hyperthermophiles

– organisms that can survive at temperatures

exceeding 100o C, such as near deep-sea vents

– Potential for biomedical and industrial application

Eukarya p.

. Eukarya includes all organisms with

eukaryotic cells

• Examples:

– plants – animals – fungi

– algae

Fungi

• History of marine mycology

– marine fungi first discovered in 1849

– marine fungi’s ecological role is difficult to evaluate; biomass needs to be quantified – important in marine ecosystems as

Fungi

• General features of fungi

– eukaryotes with cell walls of chitin – many are unicellular yeasts

– filamentous fungi grow into long, multi-cellular filaments called hyphae that can branch to

produce a tangled mass called a mycelium

– heterotrohic decomposers that recycle organic material

Fungi

• General features of fungi (con’t)

– store energy as glycogen

– kingdom Fungi is divided into 4 phyla:

• Chytridiomycota (motile cells)

• Zygomycota (e.g. black bread mold)

• Basidiomycota (club fungi, e.g. mushrooms) • Ascomycota (sac fungi)

Fungi

• Ecology and physiology of marine fungi

– can be either obligately marine, requiring ocean or brakish water or facultatively marine (primarily of terrestrial or fresh water origin)

– salinity is toxic to fungi, so they must devote energy to removing sodium

– most marine fungi live on wood from land – some live on grass in salt marshes

– others live on algae, mangroves or sand

Reproduction of Marine Fungi

• Marine yeasts reproduce asexually by

budding—mitosis that produces daughter

cells of unequal size

• Filamentous marine fungi reproduce

asexually by production of conidiospores on

the tips of hyphae

• Filamentous marine ascomycotes can

reproduce sexually by forming a fruiting

Maritime Lichens

• Lichens: mutualistic associations between

a fungus and an alga

– fungi are usually ascomycotes

– algae are usually green or blue-green bacteria

• The fungus provides attachment, general

structure, minerals, moisture

Stramenophiles

• A diverse group of eukaryotic organisms

unified by the nature of their cells’ 2

flagella

• The special flagella

– 1 flagellum is a simple form, usually with a light-sensing body at the base; senses light – 2nd bears many mastigonemes (hair-like

Stramenophiles

• Heterokont: refers to the different form of

the 2 flagella

• Ochrophytes: photosynthetic type that are

usually golden brown

Eukarya p.

. Eukarya includes all organisms with

eukaryotic cells

• Examples:

– plants – animals – fungi

– algae