Q.77 Which of the following cocci is/are examples of division in one plane?
(A) Staphylococci
(B) Streptococci
(C) Micrococci
(D) Diplococci

Streptococci divide in one plane, forming chains, making option (B) correct. Diplococci also divide in one plane but separate into pairs after a single division. Staphylococci and Micrococci divide in multiple planes, forming clusters or tetrads, respectively.​

Option Analysis

Staphylococci (A)
Staphylococci, like Staphylococcus aureus, divide in three perpendicular planes, creating irregular grape-like clusters. Successive divisions occur in alternating orthogonal planes, preventing chain or pair formation.​
This multi-plane division distinguishes them from single-plane cocci.​

Streptococci (B)
Streptococci divide repeatedly in one plane (parallel divisions) and remain attached, forming long chains. Examples include Streptococcus pyogenes and Streptococcus mutans.​
This arrangement is a classic hallmark of one-plane division in cocci.​

Micrococci (C)
Micrococci typically divide in two perpendicular planes, resulting in tetrads (groups of four cells). They rarely form single-plane arrangements like chains or pairs.​
Their cuboidal or clustered morphology confirms multi-plane division.​

Diplococci (D)
Diplococci, such as Neisseria gonorrhoeae or Streptococcus pneumoniae, divide once in one plane but separate quickly into pairs. They do not form chains from repeated single-plane divisions.​
While the division plane is single per cycle, the arrangement differs from streptococci.​

Correct Answer

(B) Streptococci. This matches standard microbiology classifications for cocci dividing in one plane to form chains.​

Cocci division in one plane is a key microbiology concept for CSIR NET aspirants, distinguishing bacterial arrangements like chains in Streptococci from clusters in Staphylococci. This guide breaks down Staphylococci, Streptococci, Micrococci, and Diplococci based on their division planes.​

Bacterial Cell Division Basics

Cocci bacteria divide by binary fission, but the plane of division determines their arrangement. Single-plane division yields pairs (Diplococci) or chains (Streptococci); two planes form tetrads (Micrococci); three planes create clusters (Staphylococci).​

Detailed Examples

• Streptococci: Chains from repeated one-plane divisions; e.g., S. pyogenes.​

• Diplococci: Pairs after one-plane division; e.g., Neisseria spp.​

• Micrococci: Tetrads from two-plane divisions.​

• Staphylococci: Grape-like clusters from three-plane divisions.​

Exam Relevance

For competitive exams, recognize Streptococci as the primary example of cocci division in one plane forming chains. Practice with Gram staining and morphology visuals for mastery.