Question

Choose the wrong match for the shapes of bacteria:
a. Coccus – Spherical
b. Vibrio – Comma
c. Spirillum – Rod-like
d. Bacillus – Rod-like

Answer 1

Bacteria are the most important and abundant microorganisms. They are found everywhere, in soil, water, and air. They are even present in extreme environments where it is very difficult to survive, such as snow, hot springs, deserts, etc. Depending upon the shape, bacteria are of many types.

Complete answer:
As discussed above, there are many shapes of bacteria known but the most important four categories are- coccus, bacillus, vibrium, and spirillum.

Coccus (plural – cocci) is spherical or oval shaped bacteria. It has two major categories – diplococcus (arranged in pairs) and streptococcus (many). It ranges from 0.5 micrometre to 1 micrometre in diameter. Examples of cocci bacteria are Streptococcus pneumoniae, Neisseria, etc.

Bacillus is a rod shaped bacteria. It can be present single or in chains. When bacilli are arranged in a chain form, they are called streptobacillus. They are generally 0.5 micrometre to 1 micrometre in length. Example of bacillus is Escherichia coli.

Vibrium is a comma shaped or curved bacteria. They are 1-100 micrometre long. Example of vibrium is Vibrio cholerae.

Spirillum is a spiral shaped bacteria (twisted or curve shaped) that has a thick and rigid spiral structure. They range from 1 micrometre to 100 micrometre in size. Example of spirillum bacteria is Campylobacter jejuni. Thus the spirillum is spiral in shape and not the rod like.

Hence, the correct answer is option (C).

Note: The shape of bacteria can be determined with the help of a primary protein known as MreB. It forms a cytoskeleton under the cytoplasmic membrane of the cell and helps in forming specific patterns that eventually determine the shape of the bacteria.