Chapter 19: Bacteria and Viruses Notes

19-1 Prokaryotes

Classifying Prokaryotes

Domains are a classification above kingdom

• Eubacteria: most of the bacteria are in this category and have peptidoglycan (short chains of amino acid, peptides and carbs) in the cell walls.
• Archaebacteria: ancient bacteria that usually live in unusually harsh environments such as hot springs, stomach acid and salty water. Archaebacteria have different Cell Walls, cell membranes and ribosomal RNA than Eubacteria. They also do not have peptidoglycan in the cell walls.

Identifying Prokaryotes

• Shapes

• Cell Walls: Gram staining separates Eubacteria into Purple which are gram positive and have a thicker layer of peptidoglycan in the cell wall than Gram negative which are Pink. Gram negative bacteria have an extra layer of lipid on the cell wall that stops the purple stain from entering.

• Movement: Flagella (tails), Spiral shaped bacteria move by corkscrew motion, myxobacteria produce a layer or slime to glide in

Obtaining Energy

• Autotrophs: either use the sun to photosynthesis (photoautotroph) or they can oxidize inorganic compounds as food (chemoautotroph)
• Heterotrophs: ferment sugars or feed on dead stuff (saprophytes

Growth and Reproduction

· Binary fission is asexual reproduction where the bacteria just divide into identical cells.

· Conjugation: Bacteria make a gridge and exchange genetic material

· Transformation: Bacteria incorporate DNA from dead bacteria

· Transduction: use viruses to transfer DNA from bacteria to other bacteria.

19-2 Bacteria in Nature

Decomposers

• Bacteria help the ecosystem recycle nutrients
• Breaks down complex molecules (dead trees, corpses…) into simple molecules such as water, nitrogen compounds and CO₂

Nitrogen fixers:

• N₂ Can’t be used directly because of the triple bond
• Must be “fixed” to ammonia
• Rhizobium grows in nodules of in the roots of soybeans and other legumes. It is a Mutual relationship where the plant provides nutrients for bacteria and the bacteria converts nitrogen for the plant.

Bacteria and disease:

Pathogens (disease causing agent)

• Damage tissue or the infected area (ex. Tuberculosis bacteria break down lung tissue)
• Release toxins that harm (Streptococcus: strept throat cause a rash or e-coli food poisoning is caused by toxins released)
• Antibiotics stimulate the immune system to fight bacterial infection.
• Penicillin and tetracycline block the growth and reproduction of bacteria.

Human Uses of Bacteria

• Make cheese, yogurt, buttermilk, sourcream, pickles, sauerkraut and vinegar.
• Digest petroleum in spills
• Synthesize drugs (insulin, hemoglobin)
• Heat stable enzymes in bacteria from Yellowstone hot springs

Controlling Bacteria

• sterilization

• disinfectants
• refrigeration
• boiling, frying, steaming, microwave
• salt

19-3 Viruses

• Latin word for poison
• Viruses are not living things because they are not able to reproduce independently
• Structure: Protein coat (capsid, that surrounds a core of DNA or RNA)

Lytic cycle- virus enters the cell, make copies of itself and causes the cell to burst.

Lysogenic cycle- a virus imbeds its DNA into the DNA or the host cell and is replicated along with the host cell’s DNA. Bacterial DNA called prophage.

Virus and Disease

• Adenoviruses: Polio, AIDS, measles, mumps, yellow fever, colds flu
• Vaccine stimulates the immune system providing immunity to killed viruses or viral proteins injected. The body makes antibodies.
• Oncogenic viruses; disrupt normal controls on cell growth causing cancer
• Retroviruses- Usually RNA is copied from DNA but in retroviruses DNA is copied from the viral RNA. AIDs is a retrovirus

Prions:

• Mad Cow and Scrapies are prion diseases. There are no DNA or RNA, just proteins.
• TSE Transgenic Spongiform encephalitis is the human form of Mad Cow. Proteins that come in contact with the prion unwind. This makes holes in the brain so the brain looks like a sponge.