naked viruses
- contain nucleocapsid
- lack envelope
- more resistant to disinfectant
envelope viruses
- contain nucleocapsid
2. have envelope
viral genome
- can be either DNA or RNA
- liner or circular or fragmented
- double or single stranded
capsid composition
cover with protein coat –> protein coat is made up of capsomers
envelope composition
made up of lipid layer
spike –> animal viruses
tail fiber –> phages
(no comment)
three types of bacteriophage life cycle
- lytic phages –> productive infection ALWAYS
- temperate phages –>
- filamentous phages –> productive infections not by cell lyse but by inhibit growth of host cell
5 steps of lytic phage infection (ex:T4 infection)
- attachment - tail fiber bind to cell wall or pilli or flagella receptor
- genome entry and uncoat - lysozyme degrades cell wall -> genome injected
- synthesis - Early protein made = nuclease degrade host DNA, protein modifies host’s RNA polymerase to not able to recognize its promotor.
- Late protein made = strutural protein for tail fiber and capsid - assembly or maturation - protein capsid form and genome packaged
- release - cell lyse from lysozyme of phage, new phage particles are released
lysogenic path
attachment –> inject phage DNA into bacteria –> prophage is integrated into bacterial chromosome –> cell devide –> excision of phage DNA
intergrates phage DNA in bacteria chromosome via ____
specific recombination
a ____ protein maintains lysogenic state
repressor
Phage induction
allows phage to escape damaged host cell. How? DNA repair is activated by the damage thus activated PROTEASE, and this protease destroy REPRESSOR protein
example of phages
lytic phage example T4
temperate phage example lambda phage
filamentous phage example M13
steps of filamentous phage infection
- attach to “F pilli” or bacteria
- single strand DNA enter cytoplasm of host
- DNA polymerase of host synthesize complementary strand of phage DNA
- phage coat protein insert into host cytoplasmic membrane
- extrusion = phage DNA exit the membrane and host protein coat the phage DNA creating a nucleocapsid
acute infection
a. rapid onset
b. short duration
persistent infection
a. may or may not have symptoms
b. continues for years or life time
persistent infection divides into chronic and latent infection
+ chronic infection - continuous production of low levels of virus particles
+ latent infection - viral genome is silent, can’t be eliminated, can be reactivated
proto-oncogenes and tumor supressor genes
govern growth and division of cell –> prevent tumor
viral oncogenes
interfere with proto-oncogenes and tumor supressor –> cause tumor
