Micro Basics

Question 1

superoxide dismutase

Answer 1

breaks down superoxide radical to H2O2 and oxy

Question 2

catalase

Answer 2

breaks down hydrogen peroxide to water and oxy

Question 3

peroxidase

Answer 3

breaks down hydrogen peroxide

Question 4

aerobes

Answer 4

oxy required for growth

possess enzymes capable of breaking down superoxide radical and hydrogen peroxide

Question 5

microaerophiles

Answer 5

aerobe that requires reduced oxy (2-20%)

possess low levels of enzymes for breaking down superoxide radical and hydrogen peroxide

Question 6

capnophiles

Answer 6

aerobe that grows better in inc CO2 environment (5-10% CO2)

Question 7

anaerobes

Answer 7

oxy inhibits growth

don’t have superoxidase dismutase or catalase

Question 8

aerotolerant

Answer 8

anaerobes that can survive being exposed to air but cannot initiate growth if oxy is present
**can tolerate short oxy exposure

Question 9

facultative organisms

Answer 9

can grow w/ or w/o oxy
*most human pathogens
commonly found in GI/GU tract

Question 10

characteristics of bacterial genome

Answer 10

circular
ds DNA
supercoiled

Question 11

plasmid

Answer 11

extrachromo genetic element w/ replication origin (can replicate independently)
5-100 genes
can be passed during cell division or transferred between bacteria by conjugation or transformation
usually confer resistance or virulence factors

Question 12

transposon

Answer 12

mobile genetic element contained on chromosome or plasmid
1-10 genes
doesn’t replicate independently
can jump from 1 site to another w/in the same DNA molecule or to a different DNA molecule

Question 13

fates of newly transferred DNA piece? (3)

Answer 13

1. degradation
2. replication as plasmid
3. integrated into recipient chromo or plasmid

Question 14

generalized transduction

Answer 14

mediated by lytic phages
random fragments of degraded bacterial DNA (or plasmids) are mistakenly packaged into the assembling phage head –> injection via phage
–> bact chromo piece recombine w/ host DNA
–> plasmid replicates
–> transposon inserts into host plasmid or chromo

Question 15

specialized transduction

Answer 15

mediated by temperate or lysogenic phage

bact DNA next to prophage is accidentally spliced out and packaged

Question 16

lysogenic conversion

Answer 16

nonvirulent bacterial strains become virulent due to acquisition of virulence genes carried by transducing phage
only bacteria that are lysogenized by the phage carry the virulence genes

Question 17

resident microbiota

Answer 17

present for months or longer in a particular site

adapted to host

Question 18

transient microbiota

Answer 18

may become briefly established by then out competed by resident microbiota or suppressed by body’s defenses

Question 19

ways invading bacteria attach to host after entry? (2)

Answer 19

1. adhesins allows bact to bind to specific receptors on host cell surface
   e. g. lipoteichoic acid (staph aureus)
   e. g. pili (e coli)
2. biofilms (mats of immobile organisms)

Question 20

quorum sensing

Answer 20

used to turn on biofilm formation genes and modulate expression of virulence factors
bact aggregate –> release and detect signal molcules/autoinducers –> make copius amounts of extra cell polysaccharides –> impermeable 3D biofilm

Question 21

how do bacterial damage host locally vs distantly?

Answer 21

locally via enzymes (=hemolysin if lyses RBC)

distantly via toxins

Question 22

endotoxin

Answer 22

microbial cell associated
core lipid A protein in endotoxin act C’ –> IL-1 and TNF –> fever, stock, death
e.g. LPS in game - CW

Question 23

exotoxin

Answer 23

proteins secreted by gram + and - bact
lyse cells, interfere w/ neural transmission, and/or affect GI tract lining
e.g. superAg causing TSS

Question 24

vector transmission

Answer 24

animate transmission vehicle

e.g. arthropod

Question 25

sensitivity vs specificity

Answer 25

sensitivity = prob that it will be + in presence of dz, evaluates false neg
specificity = prob that it will be - if dz isn't present, evaluates false +

Question 26

what does gram - diplococci inside PMNs indicate?

Answer 26

gonorrhea

Question 27

KOH preps

Answer 27

used to look for fungi/yeast

host cells and bacteria dissolve in KOH but not fungi

Question 28

routine bacterial cultures are incubated at?

Answer 28

35-37*C for 24-48 hr

Question 29

media that inh gram + cocci but allows gram - rods to grow?

Answer 29

bile salts in McConkey agar

Question 30

media that ing gram - rods but allows gram + cocci to grow?

Answer 30

PEA (phenylethylalcohol)
CNA (colistin naladixic acid)
*good for recovering staphylococci or streptococci from specimens full of gram - (stool, peritoneal wounds)