Enterobacteria

Enterobacteria are a family of rod-shaped, aerobic, facultatively anaerobic bacteria. This means that while these bacteria can survive in the presence of oxygen, they prefer to live in an anaerobic (oxygen-free) environment. The Enterobacteriaceae family is subdivided into eight tribes including: Escherichieae, Edwardsielleae, Salmonelleae, Citrobactereae, Klebsielleae, Proteeae, Yersineae, and Erwineae. These tribes are further divided into genera, each with a number of species.

A transmission electron micrograph of Escherichia coli. Photograph by Kari Lounatmaa. Photo Researchers. Reproduced by permission.

Enterobacteria can cause disease by attacking their host in a number of ways. The most important factors are motility, colonization factors, endotoxin, and enterotoxin. Those enterobacteria that are motile have several flagella all around their perimeter (peritrichous). This allows them to move swiftly through their host fluid. Enterobacterial colonization factors are filamentous appendages, called fimbriae, which are shorter than flagella and bind tightly to the tissue under attack, thus keeping hold of its host. Endotoxins are the cell wall components which trigger high fevers in infected individuals. And enterotoxins are bacterial toxins which act in the small intestines and lead to extreme water loss in vomiting and diarrhea.