Experiment 6 - Determination Of Coliform Numbers In Water By The Membrane Filter Technique

What is the Endo medium used for?

Coliform culture

Why is Endo medium used?

It’s selective so it discourages the growth of most other species of bacteria.

What do coliform bacteria break down?

Lactose

What is the broken down lactose then formed into?

A number of simpler substances, which are a group of chemicals known as aldehydes

What does Endo medium contain?

Lactose, other nutrients, and basic fuchsin

What is basic fuchsin?

A stain that reacts with aldehyde molecules to form a shiny green complex

How are coliform bacteria further divided?

Into two types based on incubation temperature.

What are total coliforms?

Organisms that ferment lactose with the production of acid and gas forming colonies with a green sheen

At what temperature do total coliform organisms ferment lactose?

at 37°C

What are fecal coliforms?

Organisms that are able to grow and ferment lactose with production of acid and gas producing blue colonies

What do fecal coliforms grow on?

m-FC broth

What temperature do fecal coliforms grow?

at 44.5°C

What are the advantages of the membrane filter method?

• Greater sensitivity because larger volumes of water can be tested

• High degree of reproductibility or results

• Shorter time for obtaining results because it requires no confirmatory/completed tests.

What is the principal disadvantages of the membrane filter method?

• Water being tested should be free of extraneous matter otherwise the filter would be plugged quickly

What is an example of extraneous matter?

Cyanobacteria

What medium is used for total coliforms?

Endo agar

What medium is used for fecal coliforms?

m-FC basal media