Question

How do cocci and bacilli differ in morphology?

Answer 1

Hint: Bacteria are prokaryotic single-celled organisms that survive in diverse and extreme conditions. They are microscopic structures and are present in different shapes.

Complete answer:
Bacteria are the most abundant organisms that are present in almost all habitats. They are microscopic structures and hence, cannot be seen with naked eyes. They are single-celled prokaryotes that exist in large groups of millions of cells. They lack a nucleus and other membrane-bound organelles and have a simpler internal structure. The genetic material or DNA of the cell lies freely in the cell. The DNA can be supercoiled to form a nucleoid molecule or can be a circular plasmid molecule.
The bacteria can occur in both singulars as well as clustered form. The bacteria occur in various shapes and can be classified into five groups- spherical, rod, comma, spiral, or corkscrew.

The differences between the cocci and bacilli bacteria are-

Cocci Bacteria	Bacilli Bacteria
These are spherical, round, or ovoid-shaped bacteria.	These are rod-shaped bacteria.
Due to the symmetrical shape, both the axes are almost equal to each other.	Due to its unsymmetrical shape, one axis of the bacteria is longer than the other.
These bacteria mostly grow in the absence of oxygen and thus are anaerobic.	These bacteria form an endospore during aerobic growth or are mostly facultatively anaerobic. Facultative anaerobic switch to the aerobic mode in the presence of oxygen or otherwise follow fermentation.
These bacteria include both gram-positive and gram-negative strains.	These bacteria mostly include gram-positive strains.
These bacteria are arranged in a chain manner. They are also found in tetrad or bundle/sarcina form.	These bacteria are also arranged in a chain manner. They can also exist in a palisade manner.
They can exist as diplococci (pairs of cocci), streptococci (chains of cocci), staphylococci (irregular clusters of cocci) forms.	They can exist as diplobacilli (pairs of bacilli), streptobacilli (chains of bacilli), and staphylobacilli (irregular clusters of bacilli) forms.
Examples of Cocci of bacteria are- Streptococcus pneumoniae, Streptococcus pyogenes, Neisseria gonorrhoeae, Staphylococcus aureus, etc.	Examples of Bacillus bacteria are- Bacillus thuringiensis, Bacillus subtilis, Bacillus cereus, Lactobacillus, etc.

Note: The other types of bacteria found are-
1)Vibrio- These are comma-shaped bacteria and are gram-negative. Example- Vibrio cholerae.
2)Spirilla- These are spiral-shaped bacteria and are gram-negative. Example- Campylobacter jejuni.
3)Spirochete- These are corkscrew-shaped bacteria and are gram-negative. Example- Spirochaeta.