Question

Describe the shape and structure of each bacterium.

1.Streptococcus

2. Staphylobacillus

3. Diplococcus

Answer 1

● Streptococcus

Streptocci are gram positive organisms.
Size is about 0.5 to 2 μm in diameter. They are spherical or ovoid cells in pairs or chains in varying length,non motile and non sporing.

They do not contain catalase enzyme, so that it is catalase negative.

Streptococci often posess a smooth or mucoid colonial morphology.

G+C content is 34 to 46%,and the genome size is about 1.8 to 2.2 mb.

☆G+C Content:
percentage of nitrogenous bases in a DNA or RNA molecule which are either guanine or cytosine.

● Staphylobacillus

They are Gram-positive cocci about 0.5 – 1.0 μm in diameter.Occuring singly and in irregular clusters and occasionally in short chains,which are non motile and nonsporing.

Since the bacilli divides across the short axis and they cannot form clusters staphylobacillus does not exist.

●Diplococcus

Organisms of this shape exhibit cocci arranged in pairs.

The basic shapes of bacterias are
coccus (spherical), bacillus (rod-shaped), and spiral (twisted), also many bacterias shows pleomorphism.

Cocci may be oval, elongated, or flattened on one side.

When cocci bacteria exist in pairs it can be called as diplococci.ie they typically occurs in the form of two joined cells.

Examples:Neisseria spp such as N.gonorrhoea, N. meningitidis, Streptococcus pneumoniae, Moraxella spp. and Acinetobacter spp.etc.