Micro Basics Flashcards
superoxide dismutase
breaks down superoxide radical to H2O2 and oxy
catalase
breaks down hydrogen peroxide to water and oxy
peroxidase
breaks down hydrogen peroxide
aerobes
oxy required for growth
possess enzymes capable of breaking down superoxide radical and hydrogen peroxide
microaerophiles
aerobe that requires reduced oxy (2-20%)
possess low levels of enzymes for breaking down superoxide radical and hydrogen peroxide
capnophiles
aerobe that grows better in inc CO2 environment (5-10% CO2)
anaerobes
oxy inhibits growth
don’t have superoxidase dismutase or catalase
aerotolerant
anaerobes that can survive being exposed to air but cannot initiate growth if oxy is present
**can tolerate short oxy exposure
facultative organisms
can grow w/ or w/o oxy
*most human pathogens
commonly found in GI/GU tract
characteristics of bacterial genome
circular
ds DNA
supercoiled
plasmid
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
transposon
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
fates of newly transferred DNA piece? (3)
- degradation
- replication as plasmid
- integrated into recipient chromo or plasmid
generalized transduction
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
specialized transduction
mediated by temperate or lysogenic phage
bact DNA next to prophage is accidentally spliced out and packaged
lysogenic conversion
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
resident microbiota
present for months or longer in a particular site
adapted to host
transient microbiota
may become briefly established by then out competed by resident microbiota or suppressed by body’s defenses
ways invading bacteria attach to host after entry? (2)
- adhesins allows bact to bind to specific receptors on host cell surface
e. g. lipoteichoic acid (staph aureus)
e. g. pili (e coli) - biofilms (mats of immobile organisms)
quorum sensing
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
how do bacterial damage host locally vs distantly?
locally via enzymes (=hemolysin if lyses RBC)
distantly via toxins
endotoxin
microbial cell associated
core lipid A protein in endotoxin act C’ –> IL-1 and TNF –> fever, stock, death
e.g. LPS in game - CW
exotoxin
proteins secreted by gram + and - bact
lyse cells, interfere w/ neural transmission, and/or affect GI tract lining
e.g. superAg causing TSS
vector transmission
animate transmission vehicle
e.g. arthropod
sensitivity vs specificity
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 +
what does gram - diplococci inside PMNs indicate?
gonorrhea
KOH preps
used to look for fungi/yeast
host cells and bacteria dissolve in KOH but not fungi
routine bacterial cultures are incubated at?
35-37*C for 24-48 hr
media that inh gram + cocci but allows gram - rods to grow?
bile salts in McConkey agar
media that ing gram - rods but allows gram + cocci to grow?
PEA (phenylethylalcohol)
CNA (colistin naladixic acid)
*good for recovering staphylococci or streptococci from specimens full of gram - (stool, peritoneal wounds)
