Micobiology Lab Exam 1

agar

polysaccharde isolated from red algae

can be melted and solified repeatedly

most microorganisms cannot use agar as carbon and enegry source

Autoclave

reaches 121 Celsius and pressure of 15 psi

used to sterilized, glassware

sterilize used steam under pressure

Chemically defined medium

composition and amount of All ingredients is known

Chemically undefined medium

composition and amount of ingredient is not known

Enriched Medium

medium with additional nutrients for growth fastidious organism

Differnetial medium

allow you to disern between organisms based on their metabolism

selective medium

contains ingredients that allow the growth only of certain organisms

Maintenance medium

allow for the maintenance of organisms for a long time

Contamination

unwanted microorganisms end up in sterile material or culture

Bunsen Burner

Never walk away from an open flame
If the flame goes off, turn the gas off
If you smell gas, turn the gas off
Long hair need to be tied up

Using a Bunsen Burner

50cm

Use loops

loops can be used to collect microorganisms from liquid cultures or plates

Agar plates

open at 45 degree

make sure its cool

close lid and transfer bacteria

ubiquity of microorganisms

lack of attention, messy work, messy benches, leads to contamination

Diffrent fungi and bacteria

can be from food

Winogradsky column

different microorganisms have different requirements to grow and can occupy different
niches in the same ecosystem. Products of metabolism from one species can be used as
nutrient source by other species

Simple staining

single dyes are used to stain bacteria

quick and easy way to determine morphology

cant discriminate between bacteria and other morphologies

Dye positively charged

Bacteria negatively charged

Dye binds to bacteria

Gram staining

Gram positive- 1 plasma memebrane 1 thick peptidoglycan cell wall

Gram negative- thin peptidoglycan cell wall in between two plasma membranes

dye penetrates

both plasma mebranes and cell wall

Iodine

form insouble compound

Alcochol

dissolves gram lipid layer dehydrate Gram+cell wall

CVI complex

trapped inside Gram + and counterstain Gram -

Endospores

protect genome when environmnet conditions are harsh

lack nutrients

extereme temp

radiation

chemical change

sporulation

process of forming endospores

Dyes cant

enter bacterial spores

steam traps

dye inside endospores

Lactic acid-

Phenol-

cotton blue

preserve fungal structure

kills microorganisms

stains chitin

Cytochrome Oxidase-

enzyme responsible for tranfer of electron from final cytochrome to oxygen to make water.

Not present in all micoorgansims and perform aerobic respiration

Catalase

enzyme that converts toxic hydrogen peroxide to non-toxic water and oxygen

When microorganisms conduct metabolism using oxygen as a final electron acceptor, toxic metabolic products of

oxygen are produced, such as superoxide
free radicals and hydrogen peroxide

Some bacteria are highly motile because of

Flagella and Pili

Motility agar has low concentration

.4%

What fungi are present in our food?

Commercial food might have specific
species inoculated during production
• Homemade food might use
environmental fungi/yeasts in order to
ferment