Of all the cells in the human body, there are more bacterial cells than any other type. The normal flora of bacteria, that is, bacteria that are beneficial to people, reside in the mouth and intestines. This normal flora help a person digest food and fight off infections from pathogenic bacteria in the body. Three main types of bacteria exist.
Coccus Bacteria
The cocci, plural for coccus, bacteria have a spherical shape. In nature, these bacteria may exist as individuals cells or be grouped together. Cocci cells that are grouped in pairs, known as diplococci cells, are cells that do not fully separate through cell division. Some cocci cells continue to divide in large bunches, while not fully dispersing from each other after cell division. In this situation, the cocci cells form a "grape-like" structure called staphylococcus. Neisseria, the bacteria responsible for the sexually transmitted disease gonorrhea, exhibits a diplococcus formation. Members of the genus Staphylococcus include the Staphylococcus aureus bacterium, which is responsible for most common staph infections.
Rod Bacteria
The rod bacteria, also called bacilli cells,have a rod-like shape just as the name implies. While many rod bacteria exist as single cells, some rods attach end to end in long chains. Similar to diplococci cells, after cell division these rod cells don't come apart at the end. Diplobacilli formation is characterized by a pair of rod bacterium attached end to end. When strings of cells stretch longer than two cells, the term "streptobacilli" is used to distinguish them. The most common rod-shaped bacteria is E. coli. E. coli exists in nature as singular rod-shaped bacteria. Some varieties of E. coli cause severe gastrointestinal infections, while other varieties of have beneficial properties that help with food digestion.
Spirillum Bacteria
The spirilla bacteria resemble a corkscrew structure. These bacteria can move quickly due to their corkscrew movement and ability to use flagella. The flagella, a tail-like structure, either whips or spins to help the bacteria move through solution. According to Merck, spirilla bacteria cause rat bite fever. Rat bite fever is usually transmitted to humans via a rat bite. While rat bite fever alone does not typically result in death in non-immunocompromised patients, if left untreated, it can take many months to clear up.
References
- Scientific American: Humans Carry More Bacterial Cells Than Human Ones
- "Microbiology: Sixth Edition"; Lansing Prescott, John Harley and Donald Klein; 2005
- Merck: Spirillum
