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20 Cards in this Set

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What are Koch's postulates?
1) Microorganism must be present in every case of the disease

2) microbe can be isolated in pure culture

3) inoculation of pure culture into animal-> disease

4) same species of microorganism must be recovered from inoculated animal
Bacterial shapes
cocci=sphere
--diplococci=paired
--streptococci=chain
--staphylococci=clump

bacilli=rods

coccobacilli=ovoid shape

fusiform=rod tapered at both ends

vibrio=bent rod/gulls wing

spirilla=short spiral, rod like

spirochete=long spiral, weakly gram neg
Hemolysis
Alpha=
--green color on blood agar
--partial hemolysis

Beta=
--clearing on blood agar
--total hemolysis

gamma=
--no color change
--no hemolysis
bacterial cell structure
INTERNAL
Internal --
nucleoid (no nucleus)
cytosol (proteins and nucleic acids

single circular chromosome + plasmids (contain antimicrobial resistance genes, pili, etc)
bacterial cell structure:
EXTERNAL (envelope):
cell wall
Cell membrane:
--phospholipid/protein bilayer

--site of synthesis of DNA, cell wall polymers, & membrane lipids

--ETC system so cell uses O2 for energy



Cell wall
bacterial cell structure:
EXTERNAL (envelope):
Cell wall
-gives shape/structure

-helps prevent osmotic lysis & protects from phagocytosis

--Not all bacteria have cell wall: (mycoplasma, ureaplasma, chlamydia don't)
bacterial cell structure:
EXTERNAL

PERIPLASM
1) area b/t cell wall (peptidoglycan layer) and inner (cytoplasmic) membrane outer and inner wall
ONLY IN GRAM NEG!!

2)contains enzymes:
--hydrolytic, antibiotic inactivating, binding proteins
bacterial cell structure:
EXTERNAL (envelope):

CAPSULE
Hydrophilic gel, made of polysaccharides, polypeptides

--antiphagocytic and antigenic

**NOTE: not all bacteria have a capsule
Its presence makes them smooth vs rough
Can be antigenic itself, used in vaccines
Bacterial cell structure:
PILI
proteinaceous hair-like projections

common pili (fimbriae) cover cell surface

allow attachment to host cells and other bacteria (conjugation)

sex pilus=
gram negative bacilli uses this to connect to another cell to transfer a plasmid from one to another
Flagellae
distribution on cell:
1) polar/monotrichous=one end only
2) peritrichous=around cell
3) Bipolar/lophotrichous =on both ends

**Note that flagella helps identify bacteria

It propels cell, rotating at cell envelope insertion point
Endospores
-gram-positive rods

-non-reproductive (metabolically quiescent)

-survive adverse conditions (temp, pH)
Clinical importance of diff b/t gram pos and neg
gram positive thickly meshed peptidoglycan layer does not block diffusion of low MW compounds
(this means antibiotics, detergents etc, can pass thru and damage cytoplasmic membrane)

Gram neg outer LPS-containing cell membrane blocks passage of stuff to peptidoglycan layer and sensitive inner cytoplasmic membrane
6 classic Gram positive bugs
2 cocci:
-staphylococcus (form clusters of cocci)
-streptococcus (form strips of cocci)

2 spore-producing rods:
-bacillus
-clostridium

2 non-spore forming rods:
-corynebacterium
-listeria
What is unique about listeria?
It is the only gram pos organism that has endotoxin!
Gram negative organism
1 group of gram neg cocci:
-NEISSERIA
diplococcus (2 kissing coffee beans)

1 group of spiral-shaped
-SPIROCHETES

All of the rest are gram negative rods or pleomorphic
Exceptions to the gram neg/pos categorizations
1) MYCOBACTERIA=
weakly gram pos. but stain better with acid-fast stain

2) SPIROCHETES=
have gram-neg cell wall but too small to be seen with LM, so must see with darkfield microscope

3)MYCOPLASMA
No cell wall! Only have simple cell membrane, so they are neither gram pos or neg
Bacterial cytoplasmic structures
-bacterial DNA usually consist of single circle of DS DNA
(smaller adjacent circles of DS DNA called plasmids)

Bacteria=procaryotes, have smaller ribosomes (70s) than animals (80s)

Bacterial ribosomes have 2 subunits:
-large 50S & small 30S
-these #'s relate to sed rate
-antibiotics can target these subunits specifically and block prot syn only in prok not euk!
enzymes that some bacteria have to break down ROS
1)catalase: breaks down H202

2)Peroxidase

3)superoxide dismutase: breaks down superoxide radical
oxygen spectrum: 3 types
1) OBLIGATE AEROBES=
-use glycolysis, TCA cyle and ETC with O2 as final e- acceptor
-have all three enzymes to break down ROS

2)FACULTATIVE ANAEROBES
Prefer aerobic conditions, but CAN grow without Oxygen by using fermentation for energy

3)Microaerophilic bacteria (aerotolerant anaerobes)
-use fermentation and have NO ETC!
Can tolerate low amts of O2 because have superoxide dismutase (but no catalase

4)Obligate anaerobes
hate O2 and have no enzymes to defend against it
Carbon and energy sources
All medically impt bacteria are CHEMOHETEROTROPHS--use chemical &organic compounds like glucose for energy

*Fermentation (glycolysis) ised by many bateria for 02 metabolism. Glucose broken down to pyruvic acid, yielding ATP directly

EMBDEN-MYERHOF pathway=