Question

What (other than motility) bacterial structural (as seen with a light microscope) or biochemical characteristics could be useful in eventual identification of your bacterial species (list at least 4)? You may need to look at additional chapters in your lab book or text book.

Answer 1

Bacteria can be identified based on their cell morphology, colony morphology, biochemical properties, phage typing and molecular techniques.

Structural and biochemical poperties are most commonly employed for species level identification of bacteria in the medical laboratories.

Structural features : 1.Presence of Capsule

2. Presence of Spore and its position. These are the 2 common structural features other than flagella (motility) used for identification of bacteria.

Biochemical characterisitcs : 1.Production of hemolysins (on blood agar plate clear zone of hemolysis can be seen if they produce hemolysins)

2. Bacteria which give Oxidase test positive. Tested using oxidase reagent on a filter paper. if a bacteria colony is smeared on a filter paper containing oxidase reagent, the filter paper turns purple within seconds.

3. Production of catalase enzyme. When bacteria are introduced into a tube containing hydroen peroxide, bubbling can be seen. Bubbling is due to splitting of H2O2 into H2O and O (nascent oxygen).

4. Indole test. If bacteria is able to produce tryptophanase enzyme, the indole ring in the tryptophan present in the peptone broth is cleaved and it reacts with kovacs reagent to form a pink ring.