Summary
Cocci are spherical, bacilli are rod-shaped and spirilla are spiral.
In depth
Cocci (spheres), bacilli (rods), vibrios (commas) and spirilla/spirochaetes (spirals). Arrangement words: diplo- (pairs), strepto- (chains) and staphylo- (clusters).
Shape is maintained by cell wall and the cytoskeleton-like proteins MreB.
Shape influences motility and surface contact. Cell division plane determines arrangements. Staining and microscopy reveal shape.
Example: spirochaetes such as Treponema cause syphilis.
Shape is set by the cell wall and the cytoskeleton proteins MreB (rod shape) and FtsZ (division). Other forms include filaments (Streptomyces), spirochaetes with internal flagella (Treponema pallidum, the cause of syphilis) and appendaged cells (Caulobacter). Shape can aid motility, nutrient uptake or evasion of predators.
Arrangement results from the plane of division: streptococci divide in one plane and stay in chains, whereas staphylococci divide in several planes and form clusters. These features help in identification in the lab with a stain and microscope.
Example: Vibrio cholerae has a comma shape and a single flagellum, and swims through the gut mucus.
Frequently asked questions
What is Bacterial Shapes?
Cocci are spherical, bacilli are rod-shaped and spirilla are spiral.
Which area of biology covers Bacterial Shapes, and how advanced is it?
Bacterial Shapes is one of the 54 topics in Microbiology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Bacterial Flagella and Pili, Bacteria, Archaea.
Can you give an example of Bacterial Shapes?
Staphylococcus aureus forms grape-like clusters.
What should I learn before Bacterial Shapes?
Bacterial Shapes is a Beginner topic, so no earlier topic is required. Other Beginner topics in Microbiology that pair well with it include Microorganisms, Bacteria, Archaea.
What topics are related to Bacterial Shapes?
The closest topics to Bacterial Shapes are Bacterial Flagella and Pili, Bacteria, Archaea, Microorganisms. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Bacterial Shapes?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Bacterial Shapes. To practise the whole of Microbiology, use the Microbiology quiz.
How is Bacterial Shapes different from Bacterial Flagella and Pili?
Bacterial Shapes: Cocci are spherical, bacilli are rod-shaped and spirilla are spiral. Bacterial Flagella and Pili: Flagella propel cells while pili attach to surfaces and transfer DNA during conjugation. Read both side by side and note what each one explains.
How should I study Bacterial Shapes step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Bacterial Flagella and Pili and explain the difference aloud. Finally, take the Microbiology quiz and come back to this page for any question you miss.