1a. General Microbiology Flashcards
Which organism has exons but no introns?
Bacteria.
Which bacteria has cholesterol in their membrane?
Mycoplasmas.
Which organism has ergosterol in their membrane?
Fungi.
What is bacterial cell wall made of?
Peptidoglycan.
What is fungi cell wall made of?
Chitin, glucans, or mannans.
What is the difference between bacterimia and septicemia?
Bacterimia: bacteria in bloodstream without overt clinical signs. Septicemia: Bacteria in bloodstream (multiplying) with clinical symptoms.
What bacteria is common in the colon of breast-feed only babies?
Bifidobacterium.
What organism produces the biofilm that glues it and other oral flora to teeth?
S. mutans.
What is the primary adherence structure of gram-positive cells?
Teichoic acids. [Positive T :)]
Which organism have Pili/fimbriae and what are they used for?
Primary adherence mechanism fo most gram-negative cells.
Which two bacteria have the ability to adhere to inert material, producing biofilms?
Staph. Epidermidis, Streptococcus mutans.
Which organism has “A protein” and what does it do?
Staphylococcus aureus, it is an anti-phagocytic surface component.
What does Neisseria gonorrhoeae has to escape phagocytosis?
Pili.
Which organism has “M protein” and what does it do?
Streptococcus pyogenes; it is an anti-phagocytic surface component.
Which three bacteria has IgA proteases (destruction of mucosal IgA)?
Neisseria, Haemophilus, S. pneumoniae.
What are invasins?
Surface proteins that allow an organism to bind to and invade normally non-phagocytic human cells, escaping the immune system.
How does M. tuberculosis evade intracellular destruction?
By inhibiting phagosome-lysosome fusion.
How does Listeria evade intracellular destruction?
By quickly escaping the phagosome into the cytoplasm BEFORE phagosome-lysosomal formation.
What is LPS and who produces it?
It stands for Lipopolysaccharide (an ENDOTOXIN) and is part of the gram-negative outer membrane. The toxic portion is lipid A and generally it not relesased (and toxic) until death of cell. It is heat stable and not strongly immunogenic so it cannot be converted to a toxoid.
Which organism releases lipid A even when the cell is not dying?
N. meningitidis, which over-produces outer membrane fragments.
What are exotoxins and who produces them?
Are protein toxins, generally quite toxic and secreted by bacterial cells (some Gram+ and some G-).
How come exotoxins can be processed to be used as vaccines?
Because they can be modified by chemicals or heat to produce a toxoid that still is immunogenic, but no longer toxic so it can be used as vaccine. It has an “A-B” component.
What does the “B” part of the “A-B” component of exotoxin do?
The B component binds to specific cell receptors to facilitate the internalization of A component.
What does the “A” part of the “A-B” component of exotoxin do?
The A component is the active (toxic) component (often an enzyme such as an ADP ribosyl transferase).
What do cytolysins do?
Lyse cells from outside by damaging membrane.
