Microbiology Flashcards
(32 cards)
what does gyroase topoisomerase do?
it nicks and unwinds bacterial DNA
what is the bacterial cell wall made from?
peptidoglycan AKA murein
what are the two components of the bacterial cell wall?
MurNAc and GlucNAc (n-acetylated muramic acid and N-acetylated glucosamine)
what is the process of linking MurNAc and GlucNAc called?
trans-glycosylation
how are different MurNAc and GlucNAc strands crosslinked?
using D amino acids on MurNAc via trans-peptidation
what is the additional cross-linking in the cell wall that is found in Gram positive cells?
pentaglycine chain linkers between 3rd and 4th amino acids on opposing strands
what are bacterial capsules?
carbohydrate and protein layers that are on the outermost surface of bacteria
what is the purpose of bacterial capsules?
prevent phagocytosis by preventing complement fixation (though if marked by antibodies can still be phagocytosed)
what type of bacteria forms spores?
Gram positive
what are fimbriae/pili?
they are hairlike projections that allow bacteria to adhere to surfaces as well as help in conjugation
what is the membrane composition of gram positive bacteria?
you have one inner membrane, then an incredibly thick peptidoglycan cell wall with teichoic acid and lipoteichoic acid coming off of the cell wall
what is the membrane composition of gram negative bacteria?
you have an inner membrane, then a very thin peptidoglycan wall, then a second plasma membrane which has lipopolysaccharides hanging off of it (aka endotoxin)
how does gram staining work?
you fix bacteria to medium, then stain them with crystal violet, add iodine, then decolorize with alcohol, only Gram positive will be purple and retain the stain, you counterstain with safranin which turns the gram negative ones pink
why do the gram positive bacteria retain the purple stain ?
because of their thick peptidoglycan wall
what are the three parts of lipopolysaccharides?
O antigen, core, and lipid A
what is the O antigen in the LPS?
long carbohydrate that is super hydrophillic - thus keeping out hydrophobic things like bile or antibiotics
what is the core of the LPS?
short series of sugars (heptose and ketodeoxyoctanoic acid)
what is the lipid A part of LPS?
it is the lipid part that sticks into the bacterial membrane
what does endotoxin/LPS bind to on human cells?
toll-like receptors, it triggers the release of cytokines and causes inflammatory response
what is a fomite?
an inanimate object that can transfer disease (i.e. that microbes can survive on)
what are the 4 phases of bacterial growth?
lag phase, logarithmic phase, stationary phase, death
what are obligate aerobes?
bacteria that need oxygen to live, they use citric acid cycle and electron transport chain - i.e. respiration
what are obligate anaerobes?
cannot survive in oxygenated environments, rely on glycolysis and fermentation
what are facultative anaerobes?
grow in the presence or absence of oxygen - but grow more quickly in oxygenated environments; they often live close to anaerobes and “protect” them by using up the oxygen that could harm them
