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Why do some bacteria form chains or clusters after cell division?
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Bacteria
A scanning electron micrograph of gram-positive Mycobacterium tuberculosis bacteria, the cause of tuberculosis and scrofula.
Some bacteria form chains or clusters after cell division because the individual cells do not separate from one another after they reproduce. These characteristic arrangements are a result of variations in the bacterial reproduction process and are often used by microbiologists to help identify specific species.12
Depending on the species and the plane of division, these groupings can take several forms:
- Pairs: Known as diplococci.2
- Chains: Known as streptococci, which resemble a long strand of beads.12
- Clusters: Known as staphylococci, which form random, grapelike clumps.12
- Packets: Some cocci form square or cubical arrangements, such as sarcinae (packets of eight or more cells) or tetrads (groups of four).12
While rod-shaped bacilli usually occur singly, some strains also form long chains or attach to one another at random angles. These structural patterns are distinct from biofilms, which are larger, aggregated structures where bacteria may communicate via quorum sensing.1