Microbiology

Question 1

what does gyroase topoisomerase do?

Answer 1

it nicks and unwinds bacterial DNA

Question 2

what is the bacterial cell wall made from?

Answer 2

peptidoglycan AKA murein

Question 3

what are the two components of the bacterial cell wall?

Answer 3

MurNAc and GlucNAc (n-acetylated muramic acid and N-acetylated glucosamine)

Question 4

what is the process of linking MurNAc and GlucNAc called?

Answer 4

trans-glycosylation

Question 5

how are different MurNAc and GlucNAc strands crosslinked?

Answer 5

using D amino acids on MurNAc via trans-peptidation

Question 6

what is the additional cross-linking in the cell wall that is found in Gram positive cells?

Answer 6

pentaglycine chain linkers between 3rd and 4th amino acids on opposing strands

Question 7

what are bacterial capsules?

Answer 7

carbohydrate and protein layers that are on the outermost surface of bacteria

Question 8

what is the purpose of bacterial capsules?

Answer 8

prevent phagocytosis by preventing complement fixation (though if marked by antibodies can still be phagocytosed)

Question 9

what type of bacteria forms spores?

Answer 9

Gram positive

Question 10

what are fimbriae/pili?

Answer 10

they are hairlike projections that allow bacteria to adhere to surfaces as well as help in conjugation

Question 11

what is the membrane composition of gram positive bacteria?

Answer 11

you have one inner membrane, then an incredibly thick peptidoglycan cell wall with teichoic acid and lipoteichoic acid coming off of the cell wall

Question 12

what is the membrane composition of gram negative bacteria?

Answer 12

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)

Question 13

how does gram staining work?

Answer 13

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

Question 14

why do the gram positive bacteria retain the purple stain ?

Answer 14

because of their thick peptidoglycan wall

Question 15

what are the three parts of lipopolysaccharides?

Answer 15

O antigen, core, and lipid A

Question 16

what is the O antigen in the LPS?

Answer 16

long carbohydrate that is super hydrophillic - thus keeping out hydrophobic things like bile or antibiotics

Question 17

what is the core of the LPS?

Answer 17

short series of sugars (heptose and ketodeoxyoctanoic acid)

Question 18

what is the lipid A part of LPS?

Answer 18

it is the lipid part that sticks into the bacterial membrane

Question 19

what does endotoxin/LPS bind to on human cells?

Answer 19

toll-like receptors, it triggers the release of cytokines and causes inflammatory response

Question 20

what is a fomite?

Answer 20

an inanimate object that can transfer disease (i.e. that microbes can survive on)

Question 21

what are the 4 phases of bacterial growth?

Answer 21

lag phase, logarithmic phase, stationary phase, death

Question 22

what are obligate aerobes?

Answer 22

bacteria that need oxygen to live, they use citric acid cycle and electron transport chain - i.e. respiration

Question 23

what are obligate anaerobes?

Answer 23

cannot survive in oxygenated environments, rely on glycolysis and fermentation

Question 24

what are facultative anaerobes?

Answer 24

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

Question 25

what are microaerophilic aerobes?

Answer 25

need oxygen, but too much can kill them; use aerobic respiration

Question 26

what are aerotolerant anaerobes?

Answer 26

they can tolerate small amounts of oxygen but dont use respiration

Question 27

what are capnophilic organisms?

Answer 27

bacteria that thrive in carbon dioxide rich environments

Question 28

what is sterilization?

Answer 28

completely killing all microorganisms (including vegetative cells and spores)

Question 29

when would you use ethylene oxide gas?

Answer 29

to sterilize objects that are heat sensitive and cant be autoclaved

Question 30

what is disinfection?

Answer 30

killing most bacterial cells and spores on surface objects - would never put disinfected things into body

Question 31

what is antisepsis?

Answer 31

removing or inhibiting bacterial agents on the skin or body (ex: alcohol wipes, iodine, hand sanitizer)

Question 32

what is pasteurization?

Answer 32

heating food to a certain temperature in order to destroy bacteria but not food