Spread plate method

It is also used for viable count.Here a small volume of samples is spread evenly by a sterile l shaped glass rod on the surface of the culture medium.Each bacterial colony grown is considered as one Cfu.This method is commonly used to enumurate bacteria in the urine in the case of urinary tract infection.

Anaerobic culture method

The culturing of bacteria in the absence of oxygen is called anaerobic culture.It is used to grow obligate anaerobe which can grow only in the absence of Oxygen.There are several methods to culture the bacteria under anaerobic conditions

Production of vacuum, displacement of oxygen with other gases, chemical method, biological method, reduction of medium.

Production of vacuum

The vacuum desiccators are used to culture bacteria under anaerobic conditions.However this method is found to be unsatisfactory as the vacuum produced cause the distortion of both liquid and solid media.This method Never bring a foolproof anaerobic conditions and leave some traces amount of oxygen.Hence this method is least preferred.

Displacement of oxygen with other gases

In this an airtight container is used and the oxygen is displaced with gases like hydrogen,helium, nitrogen or carbondioxide.Candle jar is popular under this method.The culture plates are kept in a container and a candle is lighted inside it.It is closed by an airtight lid.The candle will burn all the oxygen inside the jar and the jar will be filled by carbon dioxide.Again this method also found to leave some residual oxygen inside the jar that may be detrimental for the growth of anaerobes.

Chemical method

The following different agent used under this method

Alkaline pyrogallol absorbs oxygen

Rosenthal method mixture of chromium and sulphuric acid.

McIntosh fildes jar 

gaspack

Pyrogallic acid 

It was introduced by butchner in 1888.The alkaline pyrogallol has the property of absorbing oxygen.Thus method employ the use of large tube containing sodium hydroxide solution to which pyrogallic acid is added.This us then placed inside an airtight jar to create anaerobiosis.

Rosenthal method A mixture of sulphuric acid and chromium is placed inside the airtight jar.They utilizes the oxygen present inside the jar to form chromous sulphate and thus produce anaerobiosis.

Biological method

This method involves the growth of aerobic bacteria along with the anaerobic bacteria.sometime the germinating seeds or chopped vegetables are also placed.however this technique is not effective.