Motility and Culture characteristics the type of growth and appearance of colony in the solid media helps to some extent in the identification of bacteria.some of the important culture characteristics are given
Motility the presence or absence of flagella can be determined indirectly by its motility.The study of mobility help to some extent in the identification of bacteria.
The commonly used methods to study motility is the hanging drop method.Here the bacterial suspension is hanged as a drop from a cover slip in to a cavity slide.on observation of the margin of the bacteria.The vibrio cholerae is identified by its characteristics darting Motility and the hanging drop method stand as a rapid method of diagnosis of cholera under emergency situation.
Biochemical characteristics
Sugar fermentation
Principle both the facultative anaerobic bacteria and obligate anaerobic bacteria are capable of fermenting simple sugar monosaccharides producing acid as the end product.The Sugar is fermented by bacteria for its energy requirements.The types of sugar that are fermented by the bacteria vary between them and hence can be used as an identification method.
Methodology The test bacterium is inoculated in the broth containing corresponding Sugar and is incubated.A pH indicator is incorporated in the medium sugar.The fermentation of medium sugar is indicated by change in colour of the white medium is due to the acid ph production lead to the pH change
Example glucose fermenters
Glucose and lactose fermenter E coli
Glucose biochemical and mannitol fermenters salmonella sp
Catalase test
Principle few bacteria possess an enzyme called catalyse that convert hydrogen peroxide a toxic end product of respiration in to oxygen and water.Hence demonstration of the catalase enzyme helps identification of bacteria.
Methodology a clean microscopic slide is Taken.A drop of 30 percentage hydrogen peroxide is placed on it.The bacterium is emulsified in the drop and observed for the production of bubbles.The presence of bubbles indicates the production of oxygen due to the catalase enzyme.
Example this test is useful in identification of staph and species
Catalase positive all species name is identified as species
Catalase negative all species name is identified as species
Culture characteristics Bacterial colony
Colony and characteristic of bacterial colony Shape circular, irregular, filamentous or rhizoid.
Elevation raised,Convex,flat umbonate or crateriform
Margin entire,undulate, filiform curled or lobate
Surface smooth, rough,wavy,papillate, granular or glistening
Structure opaque, translucent, transparent.
