BIO 221 Lab Week 7: Bacteria Media's and Streak Plates

CHNOPS

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur

Nonfastidious bacteria

do not require additional nutrients to grow

Fastidious bacteria

require additional nutritional factors to grow

Forms of growth media

broth (nutrients dissolved in water) and agar (soldified media)

broth

nutrients dissolved in water, liquid media

Agar

gelatin-type material derived from red algae which solidifies at 45 C (cannot be bacterially processed)

Defined media

exact chemical composition is known

Complex media

contains CHNOPS but exact chemical composition is unknown

Enriched media

contains sources of CHNOPS plus additional nutrients

Differential media

allow distinguishing of colonies of different microbes on the same plate (specific substrate = specific enzyme)

Alpha differential media

partial lysis producing greenish zone around the growth

Beta diffrential media

complete lysis producing clear zone around the growth

Gamma differential media

no hemolysis

Selective media

suppress growth of unwanted bacteria and encourage growth of desired microbes

Luria-Bertani and ampicillin

selective media that only grows non-fastidious due to ampicillin resistance

Selective and Differential media

select for specific organisms, and then differentiate between the organisms capable of growing

Mannitol salt agar (MSA)

selective due to hypertonic enviorment and differential due to pH indicator

MSA is selective for

7.5% salt, hypertonic environment, halophiles

Halotolerant bacteria do what in MSA

grow

Non-halotolerant do what in MSA

doesn’t grow

how does MSA differentiate

contains mannitol sugar and pH indicator phenol red

What differential bacteria grows in MSA

bacteria that can ferment mannitol

Colors of MSA media

acidic pH turns yellow, neutral pH turns red, basic pH turns magenta

Eosin Y methylene blue (EMB)

selective due to basic dye preventing peptidoglycan growth and differential due to lactose sugar which favors fermentation

EMB is selective for

eosin Y and methylene blue dyes that inhibit peptidoglycan synthesis

what does gram pos do in EMB

doesn’t grow

what does gram neg do in EMB

grow

EMB differentiates based on

lactose sugar to produce acids

Bacteria that ferment lactose in EMB will form

dark purple colonies

Bacteria that doesn’t ferment will form

colorless colonies

Colors of EMB media

lactose fermentors produce purple acid, nonfermentors form colorless colonies

Aseptic technique

procedures undertaken to limit contamination of yourself and the culture