Exam 3 Flashcards
4 ways cells defend against HGT
- toxin-antitoxin system
- restriction/modification system
- CRISPR system
- secretion systems
explain toxin-antitoxin system
plasmid encodes a toxin and an antitoxin
daughters that lose the plasmid die; toxin is stable, antitoxin decomposes
daughters that retain the plasmid persist
net result is maintanence of plasmid in pop
system for degrading incoming DNA
restriction/modification system
EcoRI
restriction/modification system
restriction enzyme
cuts DNA at GAATTC
cuts DNA into 4000 bp segments
bacteria protect their own DNA from EcoRI by…
using methylase to methylate adenines on GAATTC
CRISPR abbreviation
clustered regularly interspaced short palindromic repeats
Cas1
Cas2
CRISPR
bind viral DNA at protospacer adjacent motifs (PAMs)
endonuclease
CRISPR
cuts out segment of DNA
CRISPR regions
memory bank of previous phage infection DNA
Cas9
CRISPR
surveillance protein
carries crRNA to corresponding region of virus in the case of a secondary infection
Cas endonuclease
CRISPR
degrades tagged DNA of virus in secondary infection
uses T4SS with a toxin on the tip that harms a DNA donor, preventing conjugation
Pseudomonas
discovered first PAIs (2)
1921, Frobisher and Brown
1951, Freeman
hly
alpha hemolysin
E. coli
stx
Shiga toxins
SP1-1
*Salmonella
*
Type III secretion proteins
PAI example
supergenome/pangenome
all cells in a population that an organism can share PAIs with
superbugs
combination of PAI transfer and antibiotic resistance transfer
1979 belmont report (3)
respect for persons, informed consent
beneficence
justice
animal models & pathogens:
mice
ferrets
guinea pigs
armadillos
chinchillas
zebra fish
nematodes
mice: S. enterica Typhimurium
ferrets: H. pylori
guinea pigs:M. tuberculosis
armadillos: M. leprae
chinchillas: H. influenzae, S. pneumoniae
zebra fish: necrotizing Streptococcus, Enterococcus
nematodes: P. aeruginosa
ideal animal model (4)
sx and distribution match human
acquire disease in same way
low expense
history of usefulness
nude mice
t cell deficient
neutropenic mice
no neutrophils
SCID mice
lack T and B cells
knock out mice
genetic deficiency
influence of missing gene studied
knock in mice
human gene inserted
Lewis B antigen
RBC sugar
in mice, show binding of H. pylori
gnobiotic animals
germ-free
gnobiotics lack…
normal gut immune system
naive animals
free of a pathogen of interest
CFU
one cell, 2 diplococci, 4 tetrads, etc
dose measured as…
CFUs
survival curve
fraction of surviving animals as a function of time
luxABDE
luminescence gene used in biophotonic imaging
S. pneumoniae
LD50
lethal dose 50
number of bacteria detected when 50% of animals are moribund
ID50
infectious dose 50
number of bacteria that will cause disease in the animal
ID50 graph
percentage of animals infected as a function of log(number of bacteria/animal)
competitive index =
CI = 1…
CI < 1…
CI > 1…
CI = 1; mutant is no different; gene not a virulence factor
CI < 1; mutant not as competitive as wild type
CI > 1; mutant is more virulent
direct comparison between wild type and mutant pathogens
competitive index
requirements to use CI
must be able to tell strains of bacteria apart
no trans effects
used to visualize tissue cultures
inverted microscope
limitaitons of tissue cultures
stop growing after a few generations
cells are nonpolarized
puromycin selection/PAT
transduction of viral proteins used to interrupt cell cycle in tissue culture
tissue cultures with bacteria are used to study…
invasion
used to study intracellular pathogen invasion
plaque assay
antibiotic used for plaque assay
gentamicin
explain plaque assay
pathogens allowed to attach and invade
free swimming bacteria are drained away
molten gentamicin agar is added to top cell layer, preventing extracellular transmission
plaques of intracellular bacteria measured
invasion frequency =
CFUs after gentamicin/total CFUs
actin tails with fluorescent labelling
green
chemicals used for fluorescent labelling
ethidium bromide/DNA
phalloidin/actin
anitbody/epitope (gold standard)
organ culture models
source
limitation
biopsies, circumcisions, cosmetic procedures
deteriorate in hours
batch culture stages of growth (5)
inoculation
lag phase
trophophase (exponential)
idiophase (stationary)
death phase
happens in lag phase
ribosome synthesis
happens in exponential phase
primary metabolism
happens in stationary phase
secondary metabolism
weird things
antibiotic resistance, pigments, HGT
MSCRAMM
microbial surface components recognizing adhesive matrix molecules
attachment mechanism
happens in death phase
endogenous respiration (cannibals)
infection stages of growth
exposure
attachment
colonization
persistence
spread
mode of life in environment pre-infection
stationary/poststationary
lack of nutrients, no adhesion sites, noxious substances, dryness, heat, light
bacteria inactive states
endospores
elementary bodies
myxospores
ultra-micro
safe havens for bacteria
reservoirs