microbio

Glucose Fermentation

Turns yellow in presence of acid; gas must occupy at least 10% of the Durham tube to be considered positive.

Nitrate Reduction Test

Tests for denitrification converting NO3 to N2, indicated by a large bubble in the Durham tube.

Sulfanilamide and N-ethylenediamine

Reagents added to test for presence of nitrite in nitrate reduction.

Catalase Test

A test where hydrogen peroxide is added to a microbe; bubbles indicate a positive reaction.

Indicator Organism

Microbes used to measure fecal contamination, with advantages and disadvantages for water quality assessment.

Enterobacteriaceae

Family of gram-negative rods that includes bacteria with varied impacts on health.

Coliforms

Gram-negative rods that rapidly ferment lactose and produce gas; indicators of biological contamination.

LGLB Test

A mildly selective test for coliforms.

KIA Test

Test for gram-negative bacteria to determine fermentation of lactose and glucose, and production of hydrogen sulfide.

H2S Production

Reacts with iron in the medium to produce a black precipitate indicating hydrogen sulfide presence.

Indole Production

Positive test indicated by a red ring formed at the top after adding Kovac’s reagent.

Methyl Red Test

Identifies end products from glucose fermentation; red indicates positive, yellow negative.

Simmons Citrate Test

Tests for citrate utilization; bright blue indicates a positive result.

EMB Agar

Inhibits gram-positive bacteria; lactose fermenters produce dark colonies.

Phenylalanine Deaminase Test

Tests for the deamination of phenylalanine; positive indicated by a dark green color with FeCl3.

MIO Motility Test

Cloudiness in medium indicates motility of the organism.

Ornithine Decarboxylation Reaction

Gray, blue color indicates positive result, while yellow indicates negative due to acid production.

Indole Production Confirmation

Red ring shows the breakdown of tryptophan when Kovac's reagent is added.

Lysine Decarboxylase Test

Overlay with mineral oil; gray/blue is positive and yellow is negative.

Lactose Fermentation

Purple to yellow change indicates lactose was fermented to acid.

Colilert Test

Predicts the number of coliforms and fecal coliforms in water samples.

First Microbes in Fermentation

Enterobacter and Klebsiella strains grow first, followed by lactic acid bacteria.

Lactic Acid Bacteria

Gram-positive rods and cocci producing lactic acid as the primary end product of glucose fermentation.

Fastidious Organisms

Organisms requiring media with many growth factors.

Antimicrobial Agent

Chemical that kills or inhibits the growth of microorganisms.

Cidal Agents

Agents that kill organisms.

Static Agents

Do not kill organisms but inhibit their growth.

Antiseptics

Microbicidal agents safe for application to skin and mucous membranes.

Preservatives

Static agents used to inhibit microbial growth in foods.

Antibiotics

Substances that kill or inhibit other microorganisms, including both gram-positive and gram-negative bacteria.

Zones of Inhibition Calculation

Calculation based on supplied concentration and dilution factors.

False Positive for Fecal Coliforms

Occurs if fecal coliforms are incubated at incorrect temperatures.

Pour Plate Dilution

Method using 1 mL for dilution.

Spread Plate Dilution

Method using 100 microliters for dilution.

Coliform Confirming Tubes (BGLC)

Used to confirm presence of coliforms at elevated growth temperatures.

H2S Black Precipitate

Indicates positive for hydrogen sulfide production in KIA test.

Oxidase Test Result

Negative results for oxidase in Enterobacteriaceae.

Gram Negative Rods Characteristics

All enterics are gram-negative and ferment glucose.

MIO Test Purpose

Detects motility, indole production, and decarboxylation.

Detection of Fecal Coliforms

Using MUG to indicate the presence of fecal coliforms.

MPN in Colilert Test

Most Probable Number calculated from positive pouch results.

Coliform Presence Indication

Presence of yellow color in ONPG test indicates coliforms.

False Positive Testing Conditions

Non-fecal coliforms may survive if not incubated properly.