by Erich Rosenberger M.D.

Created on: August 21, 2009

The world of microbiology is a virtual zoo of very small, mostly single-celled organisms. Since the invention of the microscope, scientists have spent entire careers peering in to the world of bacteria, viruses, and fungi. In order to make sense of the huge variety of microbiological organisms, scientists have classified them as much as possible. One of the more important categories of bacteria are the cocci.

The term "coccus" in microbiology simply means "round" or "spherical" in shape. The plural of coccus is cocci. This is a very broad category that is simply intended to describe basic appearance. It does not address anything other than simple shape.

There are a great many specific bacteria that are categorized as cocci. Although most of the cocci are very small individually, they are hardly even found alone. Rather, cocci team up with others of the same species and form colonies and groups. These groups can take on larger shapes.

A large number of cocci bacteria are pathogenic (disease causing) to humans. Some of the more common bacterial infections are in fact caused by bacteria that are cocci. Let's take a look at some of the more common cocci that are important to humans.

The Neisseria bacteria are cocci that are often found in pairs. This grouping makes them diplococci, meaning "two cocci". The Neisseria genus includes the bacteria that cause gonorrhea and meningitis. In addition to those two, there are many more diplococci that do not cause harm to humans.

The Streptococci are common bacteria that organize in to chains. There are many different sub-groups of the stretococci. In fact, they are even called Group A, B, C, D, and G (don't ask what happened to E and F, they just skipped over those letters). Depending on the specific species, the streptococci can cause disease ranging from strep throat to rheumatic fever. They can also cause pneumonia, meningitis, scarlet fever, and necrotizing fasciitis. A great deal of research goes in to these bacteria because they are do harmful.

The last significant group of cocci are the staphylococci. These are commonly found in clusters, often referred to as "grape-like" in appearance. There are literally dozens of different species in the staphylococci family, many of which are harmful to people. Staph infections are commonly seen in food poisoning. The infection MRSA, which is a big problem in many hospitals, is a member of the staphylococci family.

There is certainly a lot more that could be learned about the cocci family of bacteria. This article only serves to be a mere introduction and overview of the topic. You could study the details of the cocci bacteria for a lifetime and not learn everything there is to know.

Learn more about this author, Erich Rosenberger M.D..
Click here to send this author comments or questions.