LEQ: How does microbial DNA impact our lives?

1. LEQ: How does microbial DNA impact our lives? 10.17 to 10.23

2. Viral life cycles

3. Viral Life Cycle Lytic – viral replication cycle resulting in the release of new viruses by breaking open the host cell. Viral DNA directs host cell to make new viruses. Lysogenic – viral replication cycle in which the viral genome is incorporated into the host chromosome as a prophage – new phages are not produced and host is not destroyed

4. RNA Virus Reproductive Cycle 1. Envelope of virus fuses with cell membrane 2. Enzymes remove protein coat 3. Viral enzyme uses the viral RNA genome as a template for making complementary RNA which can do 2 things 4. produce viral protein 5. produce more viral RNA 6. New protein coats surround new RNA 7. Virus leaves the cell by coating themselves with cell membrane

5. Herpes virus • Enveloped DNA virus that reproduces in the host cell nucleus • Can remain dormant in certain nerve cells for long periods of time • Stress activates herpes virus flare ups

6. Polio Virus • This virus attacks nerve cells which do not divide  damage is permanent • Treated with vaccine

7. Plant Viruses • Stunt plant growth & diminish crop yields • Common plant virus – tobacco mosaic • Viruses enter through damaged tissue • Viruses transmitted to plants via… • insects, gardeners and farmers using contaminated tools, infected plant to offspring • How would a virus spread through an individual plant? • plasmodesmatta

8. Emerging Viruses AIDS – Acquired Immune Deficiency Syndrome Caused by HIV – a RETROVIRUS (uses reverse transcriptase) early 80’s 1st cases in US in San Francisco Infects and kills several kinds of white blood cells

9. Retrovirus • RNA virus that reproduces by means of a DNA molecule; it reverse transcribes its RNA into DNA; its DNA is inserted into the chromosome; its DNA then transcribes the production of more viral RNA and viral protein • AIDS is a retrovirus because it has… • 2 copies of RNA • Reverse Transcriptase Acquired Immune Deficiency Syndrome and Human Immunodeficiency Virus - are named for what they do - wipe out the immune system.

10. RNA Retro Virus 1. Viral envelope fuses with cell membrane 2. Enzymes remove protein coat 3. Reverse transcriptase converts viral RNA into DNA 4. DNA is integrated into host DNA 5. Viral genes are transcribed to produce more viral RNA and protein 6. New viruses are assembled 7. New viruses exit the cell taking host cell membrane with them *Retroviruses can be dormant for years before being expressed

11. Emerging Viruses Ebola Recognized in 1976 in Central Africa Causes hemorrhagic fever, vomiting, massive bleeding and circulatory failure – often fatal

12. Emerging Viruses West Nile First seen 1990 in North America Causes encephalitis (swelling of the brain) Spread by mosquitoes

13. Emerging Viruses SARS – Severe Acute Respiratory Syndrome February 2002 in China Within 3 months 8,450 were infected – 10% died Caused by corona virus

14. Emerging Viruses H1N1 / Swine Flu 2009 outbreak in Veracruz, Mexico Typical flu symptoms Virus killed more than 18,000

15. Emerging Viruses • Mutations of existing viruses can produce new viral diseases; diseases evolve into a new species that can infect individuals who were immune to the original strain • People come in contact with other species in the process we are exposed to the viruses that infect the other species • Spread of viral diseases is rapid due to globalization (worldwide travel), promiscuity, blood transfusions, intravenous drugs, etc…

16. Bacterial DNA Transfer (1 of 3) • Transformation – the incorporation of new genes into a cell from DNA that cell takes up from the surrounding environment (Griffith)

17. Bacterial DNA Transfer (2 of 3) • Transduction – the transfer of bacterial genes from one bacterial cell to another by a phage

18. Bacterial DNA Transfer (3 of 3) • Conjugation – the union (“mating”) of 2 bacterial cells resulting in the transfer of DNA between the 2 cells

19. Bacterial DNA Transfers New DNA integration occurs by crossing over between the 2 DNA molecules – incorporating new DNA into existing DNA

20. Bacterial Plasmids • Plasmid – small circular DNA found in bacteria (and yeast) that is separate fro the chromosome • F Factor – a piece of DNA that can exist as a plasmid; it carries the genes needed to make sex pili & other structures needed for conjugation; F = Fertility; allow for the spread of DNA to other cells

21. Bacterial Plasmids • R Plasmid – bacterial plasmid that carries genes for enzymes that destroy particular antibiotics – result in antibiotic resistant bacteria.