Bacteria Available in the Li Lab

This page provides a list and descriptions of the bacteria available in the Li lab. If you are unfamiliar with culturing or working with bacteria, please refer to my other tutorials!

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Bacteria available and their growth conditions

Gram-negatives
Escherichia coli: facultative anaerobe, 37C, nutrient agar
Klebsiella pneumonia: faculative anaerobe, 37C, nutrient agar
Pseudomonas aeruginosa: strict aerobe, 37C, nutrient agar
Bacteroides dorei: strict anaerobe, 37C, blood agar

Gram-positives
Enterococcus faecalis: facultative anaerobe, 37C, brain heart infusion agar
Staphylococcus aureus: aerobe (facultative anaerobe), 37C, brain heart infusion agar
Staphylococcus epidermidis: aerobe, 37C, nutrient agar

Bacteria appearances on selective and differential medias

Bacteria Species	MacConkey	Eosin Methylene Blue	Mannitol Salt	Blood
E. coli	pink to dark-pink, dry, donut shaped, lactose fermenter	blue-black with dark centers, metallic sheen	no growth	large, cicular, grey and moist, beta-hemolytic
K. pneumonia	mucoid, pink, lactose fermenter	pink to purple, no metallic sheen	no growth	white to grey, moist, gamma-hemolytic
P. aeruginosa	colorless, irregular margin, round	colorless, irregular	no growth	white, mucoid, beta-hemolytic
E. faecalis	limited growth: small, intensely red-purple	limited growth: small, translucent	yellow, mannitol fermenter	small, white, irregular margins, gamma-hemolytic
S. aureus	no growth	limited growth	yellow, mannitol fermenter	light to golden yellow, beta-hemolytic
S. epidermidis	no growth	limited growth	yellow	white, raised, gamma-hemolytic

Agar Types

Nutrient agar is a general purpose medium that supports the growth of a wide variety of non-fastidious organisms. It typically contains tryptone, yeast extract, agar, and sodium chloride
Tryptic soy agar (TSA) is a general purpose medium used for a wide range of applications. It typically contains tryptone, "soytone", sodium chloride, and agar.
Blood agar is a differential media. Typically, blood agar plates are supplemented TSA plates, with 5-10% mammalian blood enrichments. These plates are able to detect hemolytic activityand are used to isolate fastidious organisms.
Eosin methylene blue (EMB) is a selective stain medim for Gram-negative bacteria. The dyes in this medium are toxic to Gram-positive bacteria. This media can differentiate based on lactose fermentation: bacteria that ferment lactose will appear with a dark center.
MacConkey agar is another selective and differential media for Gram-negative and enteric bacteria. This medium also differentiates based on lactose fermentation, where lactose fermenteres appear pink or red.
Mannitol salt agar (MSA) is used to select for salt-tolerant bacteria. Because it contains a high concentration of NaCl, it is selective against most Gram-negatives and selective for some Gram-positives (Staphylococcus, Enterococcus, Micrococcaceae, etc). This medium can also differentiate based on mannitol fermentation as it contains a pH indicator for mannitol fermentation (the agar will turn yellow).
Brain heart infusion agar is a nutrient-rich general media for fastidious microorganisms.
Chopped meat medium is a medium used for spore- and non-spore forming anaerobes.