Bacteria and Viruses: Microbial World Unveiled

1. Bacteria and Viruses Chapter 19

2. 19-1 Bacteria • Common name for all prokaryotes • unicellular organisms without a nucleus • Were all in Monera • Eubacteria • live nearly everywhere • normally protected by cell wall containing peptidoglycan - cell membrane inside of cell wall • Archaebacteria • lack peptidoglycan • DNA similar to eukaryotic DNA • most are extremophiles – live in harsh environments • methanogens; halophiles; extreme thermophiles

3. Prokaryotic Body Plan DNA capsule plasma membrane ribosomes in cytoplasm bacterial flagellum pilus cell wall cytoplasm

4. Identifying Prokaryotes • Shape a. bacilli(us) – rod-shaped b. cocci(us) – spherical c. spirilla(us) – spiral and corkscrew shaped 2. Cell Walls a. Gram-positive – have thick peptidoglycan cell walls that take and hold stain b. Gram-negative – thinner cell walls with lipids on outside – does not hold stain 3. Movement

6. Metabolic Diversity • Chemoheterotrophs – must take in organic molecules for energy and a supply of carbon 2. Photoheterotrophs – use photosynthesis for energy, but take in organic compounds for carbon source 3. Photoautotrophs – use photosynthesis for both energy and carbon source 4. Chemoautotrophs – use chemosynthesis – get energy from chemical reactions and use carbon dioxide as carbon source

7. Releasing Energy • bacteria release energy by cellular respiration and fermentation • Obligate Aerobes - require a constant supply of oxygen B. Obligate Anaerobes - must live in the absence of oxygen C. Facultative Anaerobes - can survive with or without oxygen

8. Growth and Reproduction • under good conditions bacteria can reproduce every 20 minutes Binary Fission • normal asexual reproduction of bacteria • replicate DNA and then divide Conjugation • exchange of genetic material between bacterial cells • increases genetic diversity Spore Formation - allows survival of bad conditions for a long time

9. DNA replication begins Prokaryotic Fission - 1 Bacterium before DNA replication bacterial chromosome Figure 21.7 Page 350

10. Membrane growth moves DNA molecules apart DNA replication completed parent DNA molecule DNA copy Prokaryotic Fission - 2

11. New membrane and cell-wall material deposited Cytoplasm divided in two Prokaryotic Fission - 3

12. nicked plasmid in donor cell conjugation tube to recipient cell Conjugation Transfer of plasmid

13. Importance of Bacteria • while we usually think of bacteria negatively they are actually essential to correct functioning in ecosystems • Decomposers - primary decomposers who make nutrients available to plants - used in sewage treatment plants also B. Nitrogen Fixers - Rhizobium in nodules of legume roots fix nitrogen in a form the plants can use

14. C. Human Uses • in food production • in industry – can clean-up oil spills • to synthesize drugs and chemicals • genetic engineering now has them producing human hormones • Mutualism with Eschecaria coli in our colon where they help us make vitamins

15. 19-2 Viruses - virus means “poison” What is a Virus? • non-living – no metabolism and can’t reproduce on their own • DNA or RNA core surrounded by a protein coat • use a living cell’s internal structures to reproduce themselves • Capsid – protein coat - often with proteins on it that help it invade a host cell – often highly specific • once inside the host the viral genes get the host cell to make viral proteins and DNA/RNA

17. bacteriophage – a virus that attacks bacteria Viral Infection • Lytic Infection - virus enters a cell; has copies of itself made; and causes cell to burst and release more viruses 2. Lysogenic Infection - virus enters a cell and has its DNA integrated into the DNA of the host cell - as cell replicates its DNA it also replicates the viral DNA - prophage – viral DNA embedded in host DNA

18. Lysis of host cell is induced; infectious particles escape. Tail fibers and other parts are added to coats. Virus particles bind to wall of suitable host. Viral genetic material enters cell cytoplasm. Viral protein molecules are assembled into coats; DNA is packaged inside. Viral DNA directs host machinery to produce viral proteins and viral DNA. Lytic Pathway Stepped ArtFig. 21.20 Page 358

19. Viral DNA is excised from chromosome and cell enters lytic pathway. Viral DNA usually becomes integrated into the bacterial chromosome. After binary fission, each daughter cell will have recombinant DNA. Prior to prokaryotic fission, the chromosome and integrated viral DNA are replicated. Lysogenic Pathway Stepped ArtFig 21.20 (2)Page 358

20. - may stay inactive for a long time - eventually something causes the DNA of the prophage to be activated and it enters the Lytic cycle and destroys the host cell Retroviruses • Viruses which have RNA as genetic material • When they infect a cell the cell first makes DNA from RNA template (reverse transcription) • DNA inserts into cell’s DNA and can stay dormant • Can cause some cancers, HIV causes AIDS, colds (Copy Figure 19-11)

21. 19-3 Diseases Caused by Bacteria and Viruses While most bacteria and viruses are not harmful a few are pathogens (disease causing) • Disease results when a virus or bacteria interfere with the host’s ability to get enough nutrients or energy • Louis Pasteur developed the Germ Theory of Disease when he proved that bacteria can cause disease Bacteria cause disease by directly breaking down cells for food or by releasing toxins that travel throughout the body and interfere with normal activity in the host.

22. Vaccines are used to stimulate the immune system by exposing it to a dead or weakened pathogen. • Antibiotics are used against bacterial infections that the immune system doesn’t beat. • Bacteria can be controlled by sterilization with heat; disinfectants; and correct food processing and handling.

23. Lyme Disease

24. Viral Disease • Viruses produce disease by disrupting the body’s normal equilibrium • Most viruses are very specific in what cells they attack – polio only attacks motor neurons • Viral infections cannot be treated with antibiotics.