LAB EXAM 2- MICROBIOLOGY

TDP & TDT

TDP = temperature to kill all microbes in 10 minutes

TDT = time required to kill microbes at a given temperature

Higher resistance

Endospores

Gram-positive bacteria

Thick cell walls

Hypotonic

Cell bursts

Solute concentration inside a cell exceeds that outside the cell, causing water molecules to move into the cell, possibly leading to swelling and possibly lysis

Hypertonic

cell shrinks (plasmolysis)

Solute concentration outside a cell exceeds that inside the cell, causing water molecules to move out of the cell, resulting in crenation (shriveling) or plasmolysis.

Spectrophotometer

Low %T = high growth

High %T = low growth

UV RADIATION

Causes thymine dimers (DNA damage)

Blocks replication and transcription

Plate lid = control (blocks UV)

KIRBY/BAUER (ANTIMICROBIAL TEST)

Large zone of inhibition = sensitive

Small or no zone = resistant

Bactericidal

kills bacteria

Bacteriostatic

inhibits growth

Disinfectants

non-living surfaces

Antiseptics

living tissue

YEAST

Saccharomyces cerevisiae = budding, fermentation

Candida albicans = opportunistic pathogen

Penicillium

brush-like structure

Rhizopus

bread mold

Amoeba

pseudopods

Paramecium

cilia

Euglena

flagella + chloroplast

Giardia

cyst and trophozoite

Plasmodium

malaria

Trypanosoma

blood parasite

Starch test (amylase)

clear zone

Lipid test (lipase)

halo

Casein test (casease)

clearing

Gelatin test (gelatinase)

Liquid

Determines an organism's ability to produce extracellular enzymes called gelatinases, which hydrolyze and liquefy gelatin, a protein found in connective tissue.

Acid production

color change

Gas production

bubble in Durham tube

TSI TEST

Yellow = sugar fermentation

Black = H2S production

Slant vs butt = shows oxygen usage

IMViC TESTS

Indole = red ring

Methyl Red = red (strong acid)

Voges/Proskauer = red (weak acid)

Citrate = blue (positive)

NITRATE REDUCTION

Red after reagents = positive

Red after zinc = negative

No color after zinc = strong positive (complete reduction)

OXIDASE TEST

Purple within 15 seconds = positive

UREASE TEST

Pink = positive

Yellow/orange = negative

CATALASE TEST

Bubbles = positive

No bubbles = negative

Always think

Substrate → Enzyme → Product → Result

Example: Urea → urease → ammonia → pink color.

VISUAL INTERPRETATION

Clear zone = enzyme activity

Black color = H2S

Bubbles = oxygen gas

Pink = basic (alkaline)

Yellow = acidic