Bacterial

Bacterial organisms are a type of microorganism that constitute a large domain of prokaryotic microorganisms. They are typically a few micrometres in length and have a wide range of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats.

Classification and identification

Bacteria are classified and identified to differentiate one organism from another and to group similar organisms by criteria of interest to microbiologists or other scientists. The often controversial classifications given to bacteria are created for convenience and are not intended to indicate philosophical views or theories about the nature of life.

Structure

Bacteria, as a group, have an incredibly wide range of physical properties. Bacterial cells are generally surrounded by two protective coverings: an outer cell wall and an inner cell membrane. However, some bacteria, like the Mycoplasma species, do not have a cell wall at all, and others, like Deinococcus, have unusually thick or complex cell walls.

Metabolism

Bacteria exhibit an extremely wide variety of metabolic types. The distribution of metabolic traits within a group of bacteria has traditionally been used to define their taxonomy, but these traits often do not correspond with modern genetic classifications.

Reproduction

Bacteria reproduce primarily by binary fission, an asexual process whereby a single cell divides into two identical cells. Under optimal conditions, bacteria can grow and divide extremely rapidly, and bacterial populations can double as quickly as every 9.8 minutes.

Role in disease

Many bacteria are beneficial, but some are pathogenic and cause infectious diseases. The harmful bacteria that cause bacterial infections are called pathogenic bacteria. Bacterial diseases occur when pathogenic bacteria get into the body and begin to reproduce and crowd out healthy bacteria, or to grow in tissues that are normally sterile.

See also

• Microbiology
• Pathogen
• Antibiotic resistance

Bacterial Resources
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