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5 types of microscopes
Purpose of Darkfield microscope
to allow the viewing of bacteria that don't take stains well like spirochaetal.
-light shone from angle bends off bacteria to make a dark background the bacteria show white/light against it.
phase-contrast microscopy
take avtg of varying slide densities.
enhances varying wavelengths via PHASE PLATE

specimen appears dark
what color is



flourescence microscopy
certain material emits energy detectable as visible light when irradiated with UV light.

Emission filter sorts out lower energy emitted light.

bacteria stain with flouresc. dye
are most bacterial stains positive or negative?
positive, because bacteria have a net negative charge.
principle of differential stain
allows to differentiate between groups of bacteria on basis of some property, usually the cell wall.

uses a primary dye and a counterstain.
negative stains - what for
to see particular characteristic that won't stain with a positive stain.

CAPSULES are only visible with neg.
capsule stain
india ink stains background so bacteria shows up as transparent
electron microscope
specimen scatters electrons based on its varying densities.

used in virology, but not very useful cuz we have better techniques.
2 major components of outer layer of bacterial cell
1. Glycocalyx
2. Cell wall
glycocalyx - what is it, why?
-the outermost layer of bacteria.
-made of polysaccharides or polypeptides
-if compact/thick = capsule
-if loosely arranged = slime layer
to protect bacteria from phagocytosis
-allows it to adhere to tissue in host.
cell wall - where, why?
Just inside bacterial glycocalyx
-To protect bacteria, maintain rigidity.

Different in Gram + and -
Layers in Gram + cell wall
1. peptidoglycan = 90%
2. teichoic acid/lipoteichoic acid = 10%
which has more layers, gram + or -
negative! thinner than positive though
3 layers of neg cell wall
1. outer membrane - made of lipopolysaccharides, lipoprotein, and porin proteins.
2. peptidoglycan
3. periplasmic space
2 cell inclusions
purpose of granule cell inclusions
store food, they're visible when stained
purpose of sporulation
survival mechanism in adverse environmental conditions like dehydration, temperature extremes, or uv light
Steps of Sporulation
1. DNA copied
2. Invaginate cell membrane btwn 2 DNAs
3. Forespore - early coat around nucleic acid.
4. Cell wall forms
5. Cell coat forms - resistant to adverse conditions, also STAIN so we see a hole.
Only 2 genera that produce spores:
Aerobic Bacillus and
Anaerobic Clostridium

both are gram positive
difference between sporogenesis and germination
sporogenesis is the forming of a spore

germination is the spore going into a vegetative state.
the four amino acids in a glycan tetrapeptide
lysine or diaminopimelic acid
peptidoglycan structure
parallel diagonal lines of alternating G/M/G/M;

G=n-acetyl glucosamine
M=n-acetyl muramic acid

M's are linked vai glycan tetrapeptide;
Tetrapeptide: M-aa-aa-aa-aa
4 types of classification of Flagella
Peritrichous - lots around
Monotrichous - one flagell.
Lophotrichous - LUMP of flag.
Amphitrichous - single flagellum at both poles!
Polar - number or singular
a bacterium that was originally a prototroph and now has developed a specific growth requirement for its media.
salt-loving bacteria - give it to its media
media enrichers
-Growth factors (blood, carbs, NaCl, Vitamins, Amino acids

enrichment media
suppresses normal flora while enhancing pathogen growth
enrichment vs. enriched media
enrichment enhances all bacterial growth

enriched only enhances growth of bacteria we want to see, not normal flora
3 components of gram negative outer membrane
-lipopolysaccharides (LPS)
-lipoproteins (anchor outer cell membrane)
-porin protein - gets nutrients/proteins into the negative wall
what is contained in the periplasmic space, what type of organism has it?
gram negative
contains enzymes for nutrient breakdown
what is a mesosome?
an extension of the cell membrane; it increases the surface area of the membrane for increased uptake of nutrients.
whats in bacterial cytoplasm?
3 things:
-chromatin - throughout the cell, no nucleus.
-ribosomes - for protein synthesis.
-granules - for food storage.
3 possible shapes of bacteria
3 structural componnts of flagella

-type of motion
a. filament
b. hook
c. basal body

important info if organism is ACID FAST:
-not whether its pathogenic or not, but at least you know its mycobac.
seen in mycobacterium, when the acid fast organisms don't take up the stain evenly.
when mycobacteria grow with cells lying end to end.
q.c. on acid fast stain?
2 organisms: red bacilli and blue cocci. so mycobacterium and staph aureus.
chemical component of mycobacterium that makes them acid-fast and resistant to decolorizing:
-Mycolic acid - waxy lipid, 60% of wall.
3 types of cell-wall deficient bacteria:
a. L-forms
b. Protoplasts/Spheroplasts
c. Mycoplasma
Lister-forms of bacteria - really are normal but their cell walls have been lost due to high penicillin doses, or high salt. Removing such conditions returns the cell wall to normal.
Protoplasts vs. spheroplasts
L-forms of Gram positive, and L-forms of Gram negative.
special bacteria that does not have a cell wall. Responsible for walking pneumoniae.
2ndary pathogens
cause a disease because a primary pathogen made the host weak
opportunistic pathogens
cause a disease because another disease or condition (not necessarily pathogen) made the host weak.
nosocomial pathogens
hospital pathogens. often resist antibioitics.
communicable vs. contagious
Anthrax is communicable from animals to humans, but not contagious between humans.

it can be given directly to a person

it can be carried by a person
components of a chain of infection:
Type of disease
Transmit method
Entry Port
Effect on host
inoculum size
Infection site
Infection type
Infection stage
Exit port
3 possible sites of infection
-localized (at point of entry)
-focal (extends beyond entry point)
-systemic (carried by blood/lymph)
5 types of infection
-subacute (may not know have it)
insidious (very slow)
asymptomatic (subclin, inapparent, carrier)
-latent - viruses are this.
4 stages of infection
incubation - entry, incubate, then symptoms.
prodrome - time betwn incub/no symptoms and symptoms of disease - impending doom
disease - fastigium is peak of symptoms.
convalescence - fewer/milder symptoms, getting better.
sometimes worse than the initial infection, the post-infection infection.
port of exit
same as port of entry; gi tract, respiratory, skin, mucosa, etc.
Infection meets Koch's postulates if:
-present in every animal with disease, not in healthy animals.
-microorg can be grown in pure culture in lab from an animal specimen.
-can inoculate healthy animal with cultured isolate and see disease.
-can isolate microorg from 2nd animal and grow in lab for identical result to original isolate.
8 steps to identify agent causing infection
1. Collect specimen
2. Direct tests
3. Inoculate media
4. Incubate
5. Observe macro morpho
6. Observe micro morpho
7. ID tests
8. Antibiotic susceptibility tests
types of specimen collection
saliva, sputum, blood, clean catch, catheter, vaginal swab/stick
3 types of direct specimen tests
direct smear - gram stain it
immunological tests - for spcfc Ag.
direct molecular tests - nucleic acid
4 types ID tests in lab
1. Biochemical - media has tests in it
2. Immunological - detect antigens
4. Serological -detect antibody in serum
4. Molecular -detect unique nucleic acid
3 methods of indirect transmission of a pathogen
-Fomite (inanimate object)
-Vector (bugbite/transfusions)
-Droplet nuclei

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