Scribe.Lecture 25+26.docx

5 Pages
Unlock Document

University of Toronto St. George
Cell and Systems Biology
William Navarre

Lecture 25 Lecture 26 43 life cycle/ life style 1. virulent (lytic) phages (dsDNA virus w tail) have one objective – get in, replicate, kill host, get out 1. are bacterial killing machines 2. other two life cycle stages don’t involve killing the host 3. temperate (lysogenic) phages (dsDNA virus w tail) can choose bw integrating into the host chromosome or make plasmid and quietly stay in cell and divide w the cell 1. if one cell goes into crisis, the phage can then go into lytic mode 4. filamentous phage (release ssDNA) don’t have tails 1. they replicate as a plasmid w/in a cell but they secrete the plasmid coated in protein w/o killing the cell itself 44 5. phages recognize cell surface receptors on bacterial prey (recognize LPS O-antigen) 6. after tail makes contact, will go into firm attachment phase and docks w porin protein 7. tail recognizes that attachment has occurred, goes through tail contractions and becomes a DNA-injection syringe 45 8. the virus starts to take over the cell (starts diverting resources away from the cell, making its own AAs and starts telling the cell to make viral proteins and viral DNA) 9. there are waves of transcription during which diff phage proteins are made 10. make proteins that make the body of the phage themselves 11. assembly of phage particles w/in the cell 12. lysis 13. phage dictates when lysis occurs and will oonly occur under sufficient number and maturity 14. lysozyme enzyme will degrade PG 46 15. T4 genome is large, encodes over 250 proteins – far more than what is needed to make the phage itself 47 16. lytic phage genomes are compact w almost no junk DNA 17. reading frames follows one after another 1. often transcribed in waves 18. early genes followed by middle genes and late genes 19. early genes are the first ones injected into the cell and bc there is no phage polymerase in the cell, it is the bacterial RNAP that transcribes these genes 1. promoters in these early genes look like bacterial promoters 2. in phage T7, one of the early genes encodes its own RNAP 3. also will encode proteins that shut down host polymerase – stop making own bacterial genes, start making phage genes 4. phage RNAP will recognize promoters of middles and late gens 20. middle genes are typically expressed by phage RNAP 1. they are the ones involved in DNA replication – they make multiple copies of the phage genome 21. late genes are the actual structural proteins 1. capsid (head) & tail 48 22. when look at minutes after infection, you see waves of transcription 23. early on, early genes are transcribed, and then shortly after, proteins appear 24. phage will start destroying the host chromosome w nucleases 1. host nucleotides will be used to make phage genome 25. DNA is packaged into the head, then tail attached 49 26. genes are laid out according to how the phage is assembled 27. the order of the genes in the chromosome 51 28. MotA is like a DNA-binding protein that guides RNAP 29. modifies host RNAP so that it stop recognizing bacterial promoters and recognizes more phage promoters 30. in this case, it shuts down host transcription with an anti-sigma factor 53 31. sigma phage makes the capsid and tail proteins, and holing and T4 lysozyme 54 32. how phages are assembled 33. assembled in linear fashion 34. 3 diff things being made 1. head is made, head is filled w DNA, a collar is put on it 2. separately, a tail is built up, tail is then plugged into the collared head 56 35. terminases recognize the packaging seq, recruits it to an empty phage (prohead), and pumps the DNA in the head in an energy-dependent fashion 57 36. when the head is full, it will snip the DNA, and bind a new prohead and putting second genome 58 37. lysogenic life cycle is where the phage can make a choice 38. if it wants to hide out in the cell and it thinks the host will survive and swim to a new location, it will piggyback on he bacteria and spread its genome around 39. will only go into lytic mode if it senses that the cell is in trouble 59 40. prophage: when phage are inserted into the host genome or replicating as a plasmid 41. lysogen: bacterium containing a prophage 42. E. coli is a lysogen for a phage if it has the phage in its gene 1. the genes are the prophage 2. a typical E. coli would carry several diff prophages in its gene 61 43. temperate phages have to sense the condition that the cell is in 44. DNA damage is the determining factor that the cell is in danger 45. DNA damage ex. mutagen, another phage injected its DNA in and is starting to chew up the hos
More Less

Related notes for CSB328H1

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.