Viruses & Bacteria
Lesson 1 Part 1
What is microbiology?
•The study of organisms that are too small to see without a microscope
•The single-celled and other very small organisms studied are called
microorganisms
•You need a microscope to see these organisms
•We classify all organisms into six different kingdoms. We will look at three kingdoms in this lesson: archaea, bacteria, and
Remember?
•Cells are the basic unit of all living things (and the smallest unit of all living things). •There are two types of cells:
▫prokaryotic cells: most are unicellular
(single-celled) and have no nucleus; contain all they need to survive within a single cell ▫eukaryotic cells: have a nucleus that
Virus
•A virus is a particle that cannot independently reproduce, but contains genetic information and can evolve.
•Viruses may cause diseases in host cells/organisms but are not
considered alive by many scientists because they do not have all the characteristics essential for life.
•A host cell is a cell of a living organism that is harmed in a parasitic relationship.
•Viruses do not reproduce, are not cells, do not use their own energy to grow or respond, do not make their own food, take in food or produce wastes.
Structure of Viruses
•Viruses have two basic parts:
▫A protein coat that protects the virus
▫An inner core made of genetic material (DNA or RNA)
•Viruses can only attach to certain cells in the host cell according to the surface
How do viruses multiply?
•Since viruses are not cells, they do not multiply using mitosis.
•The genetic material found inside the virus contains the information on how it will multiply.
•Once in a host cell, the genetic material takes over control and instructs the virus to produce the virus’ proteins and genetic materials.
•These new proteins and genetic material then assemble into new viruses.
•This process can occur very quickly or over a long period of time, depending on what host cell the virus is attached to because the virus uses the host cell’s functions to
Examples of Common Viruses
• Orthomyxoviridae – Influenza virus • Causes the flu, which is a respiratory
infection that often causes the infected person to have a fever, headache, and body aches
• Retroviridae - HIV (Human
Immunodeficiency Virus)
• Causes Acquired Immunodeficiency
Syndrome (AIDS), which is a deadly
Viral Diseases
•Viral diseases (viruses) are some of the most
widespread illnesses in humans.
•They may cause simple symptoms like a mild fever to more severe symptoms like cancers or even be fatal diseases.
•Transmission (how a person gets the virus) varies but many are transmitted by human
contact as well as tainted water or insect bites.
•Some viruses have vaccines, like influenza, or anti-viral drugs to control and prevent the
Bacteria
•Bacteria are EVERYWHERE: in your skin, inside your nose and mouth, in yogurt,
under rocks, in the ocean, …
•Some bacteria are bad, but not all!
•They were first discovered by Anton van Leeuwenhoek, the father of the
Structure of Bacteria cells
•Bacteria are prokaryotic cells, which means they are single-celled organisms that have all they need to
function and survive inside their one cell.
•They do not have a nucleus or other organelles found in typical eukaryotic cells. The genetic material is
within the cell, but not a defined area.
•Most still have a cell wall and a cell membrane, though.
•They also have a flagellum, a long whip-like structure that helps the cell move. It acts much like a
Three shapes of bacteria
Counter clockwise from
left: rod-like, spherical,
and spiral shaped
Function of bacteria
•Some bacteria are autotrophs and make their own food. Others are heterotrophs and consume other organisms or food like milk and meat and decaying organisms.
•Bacteria make energy using respiration, however most do not use oxygen!
•Bacteria cells can reproduce two ways:
Binary fission
•Binary fission is a form of asexual reproduction.
•Asexual reproduction is a process that involves one parent that can produce offspring identical to the parent.
•First the cell duplicates the genetic material.
•Then it divides into two separate cells.
•Reproduction, regardless of type, can only occur when the bacteria has plenty of food, right temperature, and other perfect conditions.
Examples of bad bacteria
• Streptococcus Bacterium
• Causes strep throat, a painful sore throat and fever.
• Mycobacterium tuberculosis • Causes tuberculosis, a highly
Prevention of bacterial growth
•Antibiotics can be used to stop or prevent bacterial growth (reproduction).
•Unfortunately, because they have been
overused over the recent years many diseases once easy to treat are becoming more difficult to treat.
•Antibiotic resistance in bacteria occurs when mutant bacteria survive an antibiotic
Resources:
• AIDS Pathology
http://medstat.med.utah.edu/WebPath/TUTORIAL/AIDS/AIDS001.html
• The Big Picture Book of Viruses
http://www.virology.net/Big_Virology/BVHomePage.html
• Flu – NIAID Fact Sheet
http://www.niaid.nih.gov/factsheets/flu.htm
• Malaria Brochure
http://www.niaid.nih.gov/publications/malaria/
• Epidemic – The World of Infectious Diseases
http://www.amnh.org/exhibitions/epidemic/index.html
• Welcome Trust Sanger Institute – Press Release on DNA of the tissue destroyer -Genome clues to Amoebic Dysentery
http://www.sanger.ac.uk/Info/Press/2005/050223.shtml
• Bacteria
