Notes Module 1 (pt 2) Flashcards
What are bacteriophages?
Bacterial viruses
What does the head of a bacteriophage consist of?
(a) Core – nucleic acid (genetic material)
(b) Capsid – protective protein around the nucleic acid
What does the tail of a bacteriophage consist of?
Sheath, tail fibers, and base with enzymatic pins
The sheath in the tail of the bacteriophage, consists of what?
i. Column of protein which connects the head to the base
ii. Reconfigures into a tube when the virus attaches to a bacterium
The tail fibers in the tail of the bacteriophage, consists of what?
protein fibers with polysaccharide tips which
help in determining the attachment site on bacterial cells
The base with enzymatic pins in the tail of the bacteriophage, serve what purpose?
to punch a hole in the bacterial cell wall through which the viral nucleic acid can enter
During the lytic cycle, how does the virus attach itself to the cell?
adsorption of virus to receptor sites on the cell membrane (cell wall of bacteria); due to random collision and proper “match” of attachment determinants
During the lytic cycle, what is the alternate way the virus enters a cell?
ALTERNATE: virion remains on cell surface and only the nucleic acid enters the cell
During the lytic cycle, what are the steps to the eclipse or synthesis phase
(1) Viral nucleic acid is transcribed into mRNA if needed
(2) Viral mRNA is translated into viral proteins
(3) New viral proteins inhibits the host’s synthetic mechanisms and normal host activity
(4) New viral nucleic acid copies are produced
(5) New viral capsids are produced
During the lytic cycle, when does the virus mature?
when new viral nucleic acid copies are packaged into new viral capsids
During the lytic cycle, how does an enveloped virus get released?
Enveloped viruses – bud through the cell membrane
During the lytic cycle, how does a non-enveloped virus get released?
Non-enveloped viruses – Lysis of the host cell
(a) Mature viruses accumulate in large groups in the cytoplasm awaiting release
(b) A viral enzyme ruptures the cell membrane, thus releasing the viruses
What is latency?
The DNA of certain viruses can incorporate into the host DNA and lie hidden (latent or dormant).
During this time the viral genes may be replicated as if they were normal host DNA. Upon certain stimuli, the viral DNA is removed from the host DNA and new viruses are produced.
In bacteria this is referred to as lysogeny (lysogenic cycle)
In regards to laboratory cultivation, what is the Isolation and identification time for viruses?
2 days to 4 weeks, depending on the virus
Although clinical parasitology is concerned with protozoans which take up their habitat in humans, the majority of them (about 20,000 species) are free living organisms found in ______ feeding on ________
soil and water;
algae, yeast, bacteria and other protozoa;
