Micro Lab Final Exam

Staphylococcus aureus, Gram positive coccus

thick peptidoglycan with thick capsule layer, antibiotic resistant

staphylococcus aureus

factors that help cells cause disease

virulence factors

Staph aureus antibiotic-resistant strains

MRSA, VRSA

Positive for?

Catalase and coagulase

What hemolysis?

Beta hemolysis on blood agar.

Proteus Vulgaris, Gram negative rod

tested on SIM agar; metabolizes catalase, indole, and reduces sulfur!!

Proteus Vulgaris

What does it cause?

Causes UTIs; highly motile/swarming

Serratia marcescens, Gram negative rod

Enterobacteriaceae family, causes UTI & Resp. infection; red pigment (prodigiosin) studied for antimicrobial & cytotoxic capabilities

Serratia marcescens

Mycobacterium tuberculosis; Gram variable rod

non-motile; cell wall made of mycolic acid, resists drugs

Mycobacterium tuberculosis

How does it function?

It is slow-growing, requires oxygen-rich environment; used for Acid Fast Stain

Escherichia coli, Gram Negative rod

faculative anaerobe, enteric; produces large amounts of catalase

E. coli

flexible, can live with or without oxygen

faculative anaerobe

produce shiga-like toxin, cell wall & flagellar antigen

E. coli serotype 0157:h7

What agar is E. coli on?

MacConkey agar

Pseudomonas aeruginosa, Gram negative rod

opportunistic pathogen found in hospitals; common for burn & cystic fibrosis pts

Pseudomonas aeruginosa

What is Pseudomonas positive for?

catalase & citrate positive

Color and Toxin?

greenish color; pyocyanin → cytotoxin

Bacillus subtilis, Gram positive rod

spore-forming bacteria found in soil, colonies form chains; most commonly studied

Bacillus subtilis

Bacillus subtilis is pos. for?

Lipase & amylase positive

What agar is used for Bacillus subtilis?

Spirit blue agar to test for hydrolyze starch

Micrococcus luteus, Gram positive coccus

produces bright yellow colonies; most common even in clean rooms

Micrococcus luteus

Micrococcus luteus formation?

Tetrad, catalase positive, and obligate aerobe.

It’s a way E. coli can gain new genetic material; traveling & picking up genes from other organisms

Transduction

selective & differential, contains crystal violet & bile salts; inhibits Gram (+) & allows Gram (-) to grow.

MAC (MacConkey Agar)

neutral red turns pink/purple, has lactose to differentiate coliforms & noncoliforms

MAC pH indicators

organism that thrives in basic environments with a pH of 9 or higher; grows best in these environments

Alkalinophile

cells intertwine like strands in a rope

Cording

mycolic acid in cell walls help cells cling together

cord factor

media that supports the growth of specific microorganisms while inhibiting others

Selective Media

methylene blue, eosin y, bile salts, & NaCl

Selective Media inhibitors

general-purpose media, does not restrict anything from growing; does not show visible differences between organisms (look the same)

Nutrient Agar

bring out differences & colors due to metabolic abilities of microorganisms to determine identification

Differential Media

Diluent

sterile water to dilute your sample

density

how many CFUs per mL

something that can combine with other substances to enhance them

catalase

Bacillus that ferments lactose; dark purple, green color

Coliforms

do NOT ferment lactose; usually lighter color & do not produce gas

Noncoliforms

gas catcher, catches CO₂ bubbles

Durham Tube

selective & differential, used for environment testing; gram pos. will not grow, while gram neg. can be identified

EMB Agar

gram-negative, typically grow (coliforms & noncoliforms); show distinct colony colors based on lactose fermentation.

Eosin & Methylene Blue Agar (EMB)

used to test for hydrogen sulfide production, indole formation, and motility in bacteria.

SIM Agar

Gram-negative bacteria, coliform & noncoliform; many are gut inhibitors

Enterobacteriaceae

made of protein from animal hooves, gelatinase enzyme to break it down

Gelatin

break down tryptophan, used in SIM agar

indole

energy releasing using sulfur in place of oxygen, not all organism can reduce sulfur

oxidation of indole

if red indicates positive for acid; if yellow indicates negative, base

Methel Red

is pH indicator; has sugar to create a byproduct of acid

phenol red broth

supports the growth of fastidious organisms and allows for the detection of hemolysis.

Blood Agar

organisms that don’t grow well on nutrient agar do better on blood agar due to their specific nutrient requirements.

fastidious organisms

partial destruction of RBCs & hemoglobin (turns it GREEN color)

Alpha hemolysis

complete breakdown of RBCs & partial hemoglobin; CLEAR color

Beta hemolysis

no destruction of RBCs or hemoglobin, keeps the red stain color or no color

Gamma hemolysis

Selective & differential; form gram negative organisms

Bromthymol Blue

No blue means organisms did not grow, while yellow indicates acid production and growth of acid-producing bacteria.

pH indicator for Bromthymol Blue

used for detecting lipid hydrolysis(requires bacterial lipase); pos. result has clearing around the colonies

Spirit Blue Agar

halophiles

salt lovers

selective for genes of gram pos. halophilic cocci; salt inhibitor

Mannitole Salt Agar (MSA)

Do rods grow on MSA?

No, because of salty condition

used to test for starch hydrolysis; use bacterial amylase to do this

Starch Agar

test for Butylene glycol fermentation, detects acetoin production

Voges-Proskauer Test

VP Test results

if positive, it turns red color at top of the tube; if negative, it turns to copperish “green” color

can turn into indole if the bacteria can make tryptophanase; add reagent Kovac to turn Cherry Red

Tryptophan

Scientific Name

Capitalize the first letter of genus name, underline both genus & species

Gram Neg. Color

pink/red

Gram Pos. Color

purple

Cocci

spherical

Bacilli

Rod-shaped

Spirillum

rigid spiral

Staphlococcus

cluster of spherical bacteria

streptococcus

chain of spherical bacteria

diplococci

pairs

tetrads

groups of 4

streptobacilli

chain of rod-shaped bacteria

palisades

rod-shaped bacteria arranged side by side

spirochete

flexible, corkscrew

vibrio

comma-shaped

Selective & differential, determines if organism can use citrate as its sole carbon source; contains citrate, bromthymol blue, and ammonium phosphate

Simmons Citrate Agar

Simmons Citrate Agar Results

if blue it uses citrate to raise pH (pos. result); negative result is green

determines if organisms can use citrate as a carbon source for growth

citrate test

determines if an organism can move through a medium; pos. growth spreads away from stab lines

motility test

tests if organisms can reduce sulfur to hydrogen sulfide (H₂S); produces a black precipitate in the medium if pos.

sulfur reduction

test if organisms can ferment lactose; if pos. it turns pink/red on MAC agar & dark green on EMB agar

lactose fermentation

positive results turn yellow on MSA; organisms can ferment mannitol

mannitol fermentation

test for Staphylococcus aureus; pos. result is clot formation

Coagulase Test

detects catalase enzyme; positive result shows bubbling due to H₂O₂

Catalase Test

Indole, Methyl Red, Voges-Proskauer, Citrate

IMViC

Yellow MSA

acid, NOT base

Colorless MAC

there is growth, but no lactose

EMB metallic green

E. coli

The organism growing on this MacConkey Agar plate is growing but the color of agar has not changed appreciably.  Which of the following is the best interpretation of these results?

The organism is a Gram-negative rod

The left side of the MacConkey Agar plate shown above shows an organism  that is __________ for ____________ fermentation. 

positive, lactose

The image above shows growth of an organism on MSA agar.  The yellow color indicates. 

the organism is fermenting mannitol