Microbiology Bacteria and Viruses

Germ Theory Proposed by Scientist: Luis Pasteur. Disease is caused by microscopic organisms that invade the body called pathogens (germs). Bacterial Pathogens (strep throat) Viral Pathogens (flu) Eukaryotic Pathogens (malaria) Fungal Pathogens (athletes foot)

Viruses Classification: None

Viruses Viruses are not alive. No cells They do not use energy like living things Cannot reproduce without a host cell Consist of a protein coat and a piece of either DNA or RNA They exist only to infect and kill cells

Virus Types All viruses function by injecting their nucleic acid into a host cell and taking over to create new viruses.

Lytic Viruses (Ex: Ebola) Immediate takeover of the cell Present in virulent (fast) viruses 1. Attach to cell 2. Insert viral DNA into host cell 3. Replicate viral DNA using host cell 4. Assemble new viruses 5. Destroy host cell to release new viruses End product is more viruses and a dead cell

Lysogenic Cycle (Ex: HIV) Delayed virus cycle; enter the host nucleus and lie dormant for a while First two steps are the same as lytic 3. Insert viral DNA into host DNA 4. Viral DNA is replicated when host cell divides 5. Virus enters the lytic cycle at any time to kill the cell *Can be manipulated for gene therapy by replacing viral DNA with a desired gene

Virus Cycles

DNA or RNA? Viruses based on DNA have no problem invading cells Polio Viruses based on RNA (called Retroviruses) have to use a protein called reverse transcriptase to turn their RNA into DNA before they can take over the cell. Mutate A LOT. Evolve/Change rapidly Flu

Fighting Viruses Because viruses actually hide inside the cells, it is very hard to treat them with medication Most viruses are killed by the immune system without meds The best fight against viruses is prevention. Vaccines can be given BEFORE a person is sick to train them immune system to fight the virus Since viruses can only survive inside a host, it is important that EVERYONE get vaccinated. If no one can catch the disease, then the disease will be gone forever. Antibiotics do NOT work against viruses because they cannot penetrate the human cell to reach the virus. Antibiotics only kill bacteria.

Bacteria Classification Domain: Archae or Eubacteria Kingdom: Monera Cell type: single-celled prokaryotes Feeding: some autotrophic, some heterotrophic Reproduction: mostly asexual by binary fission; occasional sexual reproduction for genetic variability

Domain: Archaebacteria Primitive bacteria that live in harsh environments. 3 types Methanogens Live without oxygen Extreme halophiles Live in extreme salt conditions Thermoacidophiles Love high temperatures and/or extremely acidic pH

Eubacteria Modern Bacteria classified by shape and reaction to Gram stain Bacilli: rod Spirilla: spiral Cocci: round Diplo: paired Strepto: chains Staphylo: clusters Gram Stain Positive: purple Negative: red

BACTERIA

Good Bacteria help you! Non-pathogenic bacteria are helpful Nitrogen fixing bacteria put fertilizer (nitrogen) into the soil for plants Gut bacteria help humans digest food Bacteria in the soil helps to decompose and break down waste in the environment

Pathogenic Bacteria make you sick! Antibiotics- medicine for treating diseases caused by bacteria Interfere with bacterial cell walls Must be taken as directed Not effective against viruses

Antibiotic Resistance Caused by using antibiotics too much or incorrectly Bacteria evolve (by natural selection) to resist the meds New methods or different antibiotics must be used.