lab quiz 1 Flashcards
why are multispecies microbial communities easy to grow/cultivate
good understanding of nutritional reqs
what is a cell made of
water, macromolecules (prots, lipids, nucleic acids, polysaccs, aa, FA, nucleotides, sugar)
what do all microorganisms req
C, N, O, H, P, S, Se (most also req Na, K, Ca, Mg)
what is a culture medium
nutrient mixture for growing microorganisms that can be liq or sol
why do we use agar
it is a solid culture medium and most microorgs cant digest it
what does complex media contain/what makes it special
growth factor supplements and exact nutritional chem comp is not known
what is an advantage of using solid agar medium
cells are immobilized on the surface
what is a colony
a visible mass of cells where a single invisible bacterial cell multiplied and divided into daughter cells
what does morphology dep on
ID of org (genetics), conditions it was grown in, nutrients available, physiological parameters/incubation
morph characteristics influenced are?
size, shape, margin, elevation, colour
what is a mixed culture
agar plate w colonies of dif morphologies
what is a pure culture
only one morph present
why are agar plates stored agar side up
prevents condensation from dripping onto agar and disrupting microbial growth
higher temps tend to _____ growth rate
increase
punctiform
spots and less than 1 mm in diam
round/circular
round edges/unbroken > 1 mm
irregular
uneven along edges
rhizoid
root like
spindle
growth develops in media and oval
filamentous
long, irregular interowven threads
list the five types of edges
smooth
undulate (wavy)
lobate (large indents)
irregular/erose (sharp pt’d edges)
filamentousm(thread-like)
list the five types of elevation
flat
raised
convex
pulvinate
umbonate
what are biofilms
several species of bact co existing and organized into enclosed adhesive matrix made of polysaccs, prots, nucleic acids
what are advantages of biofilms for bact
nutrient rich env
cell-cell commun
nutrient exchange
genetic exchange
protection against physical disruption, phagocytosisi, antimicrobials
what is dental plaque
microbial biofilm that forms on/bw teeth and gumline; one of the densest collections of bact in body
where do healthy humans have bact
surface tiss’s and constitute normal microflora and microbiome
what is the mouth a suitable habitat for
750 species of aerobic and anaerobic microorganisms
Streptococcus, Haemophilus, Veillonella, Actinomyces, Fusobacterium
what challenges do bact face and what do they do to overcome them
lysozyme and mechanical disruption
bact produce adherence factors that allow them to attact to gum and teeth
Ex) Streptococcus parasanguis and Streptococcus mutans attach to enamel
Ex) Veillonella and Fusobacterium to gumline
why is a brightfield microscope used
to examine ind bact cells
what does a condensor lens do
focuses light on specimen focal plane
what do you see through objective lens
a magnified real image w in the mic
what does the ocular lens do
magnifies image further
what does parfocal mean
image remains in focus as objective lens change
as the mag increases, the res____
decreases
what is res
ability of a lens to sep/distinguish bw small objects that are close together
what does the immersion oil do
replaces the air bw slide an dobjective lens (oil has same refractive index as slide)
what are the advantages/dis of a wet mount
cells are alive, no distortion and motility
hard to see cells and cell wall features
what are bact stains made of
powdered dye in water or OH
have pos charged salts//interact w neg part of bact (ionic)
what does fixation do
preserves int/ex structs of cell, inactivates enz that could affect morphology, and fixes cells so not washed away
heat fixation kills cells and destroys prots in structs
advantages of looking at multiple fields of view
increases number of obs, allowing to better differentiate morphs
as magnification increases, the diameter of the field of view_____
decreases
label parts of mic
refer to lab manual
set up koehler illum
mark spot in corner
fully raise stage (use coarse focus away)
fully raise condenser (use black circular knob away)
10X obj
aperture 10x
center dot and focus
close field diaphragm (black tab to right)
use condensor to get crisp heptagon
use field diaphragm to get edges just outside circle
ex of rod
e coli (1 um w, 2-3 um L), salmonella, shigella
ex pf cocci
staphylococcus (1 um diam), streptococcus
ex of filament
streptomyces
ex of spirochete
treponema denticola
what can overheating do
alter or lyse cell
what happens w inconsistent smear prep
low dens, hard to find; high dens, hard to correctly asses cell grpings
what will excessive washing do
partial decolorization of stained cells
if you cant see what should you do
open aperture diaphragm (do not increase light intensity)
if you lose cells at 100X, what should you do
make sure slide isnt upside down
make sure slide isnt dirty
if you lose cells during X-Y
restart at 10X by finding your ink mark (DO NOT use oil on 40X)
what does differential staining allow you to see
difs in bacterial cell structure
what is crystal violet
primary stain
what is an iodine solution
mordant (to help bind dye to target molecules by forming a three component insoluble crystal violet-iodine-cell component complex)//becomes resistant to dissolution in solvent
what is safranin
secondary stain//counterstains g neg cells pink
what colour are gram pos
purple
list 4 gram neg
Pseudomonas aeruginosa
Pseudomonas putida
Escherichia coli
Salmonella enterica
list 4 gram pos
Staphylococcus aureus
Staphylococcus epidermis
Enterococcus faecalis
Bacillus cereus
a g stain diff’s bact based on
cell wall composition and structure
what does the cell wall consist of
all cellular components that are located just outside the pm
what does the cell wall do
struct support
protection (from env and other cell or host defense mechs)
exclusion barrier
pathogenicity
what is the pm
innermost layer that surrounds bact cell
cell envelope
cell wall and pm
what is peptidoglycan
aka murein
large mesh like polymer
each subunit made of nag and nam
aa form small peptide and connect carboxyl grp of nam
subunits = glycan tetrapeptide
how are the nag/nam subunit sugars connected
covalent glycosidic bonds
what do transpeptidase enz do
crosslink chains or peptid to each of their nam-peptides
cells can crosslink and recycle their peptid subunits when_____
they are metabolically active (growing and dividing)
list the features of g pos
thick peptid
peptid outside peri space
teichoic acids (neg charge)
lipoteichoic acids (anchor pm lipids)
cell walls are strong, low lipid content, more resistant to osmotic press
gram neg feats
thin peptid w in peri space
large peri space
outermem cov linked to lipoprot
LPS (lipid A, core polysac, outer o side chain)
overall neg charge
why treat w acetone-OH
for g pos, peptid layer dehydrates which shrinks pores and traps dye
for g neg, lipids in outermem are dissolved, t/f more porous, thin payer of peptid cant retain dye and t/f decolourize
what dets whether dye-iodine complex is retained or lost
thickness and comp of bact ce;; wall
order the g stain procedure
crystal violet
iodine
acteone OH
safranin
what can lead to false stain results
too much OH (can decol g pos)
too little OH (underdecol g neg t/f get false pos)
not enough countertsain (cant see g neg)
if too much heat for fixation
cell wall damaged t/f more susceptible to decol
if not enough heat for fixation
cells will slide away
what was in the mixed cult in lab 3
Staphylococcus epidermidis
Pseudomonas putida
what are the ingredients of the TSA plate
trypticase peptone, phytone peptone, sodium chloride, agar, dH2O
what does the phytone peptone in TSA provide for bact
aa, minerals, 35% carbs
what oral cavity bact is rod shaped
Lactobacillus sp.
what oral cavity bact is cocci and form long chains
Streptococcus mutans
what oral cavity is cocci and form short chains
Streptococcus mitus
what risk group levels are the bact in lab 3
risk group level 1
when preparing a streak plate from a broth culture, when is it necessary to heat sterilize the inoculating loop
before culture transfer, after q 1, after q4
w the streak plate technique, what are the aseptic functions of the bunsen burner
sterilize the inoculating loop
flaming open mouth of culture tubes
generating a heated updraft that prevents air contaminants from settling into work surface
