The shapes and arrangement of bacteria is called as Bacterial Morphology. The shapes and arrangement of bacteria is used for bacterial classification.
The Bacteria are unicellular and Prokaryotic cells. They lack nucleus and membrane bound organelles. Due to the microscopic size of the cells, we cannot observe them by naked eyes. We need microscopes to study and observe them. Whenever we observe them under microscope, we observe their cell shape, arrangement and size. The study of of bacterial shape, size and arrangements of cells is called as Bacterial Morphology.
The bacterial population can distinguished on the basis of physical appearance and hence it is the primary method used for bacterial classification. The difference is shape and size may be due to the difference in habitat, ecology and genetic material.
Shape and arrangement of the bacteria:
The most common bacterial shapes that have been observed are spherical, rod like, comma, wavy or spiral shape. The scientists have named such shapes as coccus, bacillus, vibrio, spiral and spirochete respectively.
The bacteria appears in circular shape. it is called as coccus (in singular) or cocci in plural.
Arrangement of Spherical bacteria –
|Diplococci – Two cocci in pair||Moraxella catarrhalis, Neisseria gonorrhpeae|
|Tetracocci – four cocci arranged in cube like structure||Aerococcus, Pediococcus|
|Staphylocci – cocci arranged in grapelike cluster||Staphylococcus aureus|
|Sarcina – cubical packets of 8 cell in 3 planes||Sarcina ventruculi, Sarcina ureae|
The Bacteria appear in rod shape
Arrangement of rod shape bacteria –
|Diplobacilli – two bacilli in pair||Coxiella burnetti, Moraxella bovis, Klebsiella rhinoscleromatis|
|Streptobacilli – Bacilli are arranged in chains||Streptobacillus moniliformis|
|Coccobacilli – short and stumpy, appear like ovoid||Haemophilus influenzae, Gardnerella vaginalis and Chlamydia trachomatis|
|Palisades – fencing like structure||Corynebacterium diptheriae|
Other shapes of bacteria:
Bacteria are also found in shapes other than spherical and rod.
|Wavy or spiral (flexible)||Spirilla||Campylobacter jejuni, Helicobacter pylori, Spirillum winogradskyi|
|Wavy or spiral (rigid)||Spirochetes||Leptospira interrogans, Treponema pallidum, Borrelia recurrentis|
|Variable shape – cannot define the shape||Pleomorphic||–||Mycoplasma genitalium|
The bacteria are found in different shapes and arrangement. Their physical appearance information is used for bacterial classification.