Spirochaeta
Classification
Domain Bacteria; Phylum Spirochetes; Class Spirochetes; Order Spirochaetales; Family Spirochaetaceae [Others may be used. Use NCBI link to find]
Species
|
NCBI: Taxonomy |
Genus species
- Spirochaeta africana
- Spirochaeta alkalica
- Spirochaeta americana
- Spirochaeta asiatica
- Spirochaeta aurantia
- Spirochaeta bajacaliforniensis
- Spirochaeta caldaria
- Spirochaeta coccoides
- Spirochaeta halophila
- Spirochaeta isovalerica
- Spirochaeta litoralis
- Spirochaeta smaragdinae
- Spirochaeta stenostrepta
- Spirochaeta taiwanensis
- Spirochaeta thermophila
- Spirochaeta xylanolyticus
- Spirochaeta zuelzerae
Description and Significance
The genus Spirochaeta represents a group of free-living, saccharolytic non-pathogenic, obligate or facultative anaerobic helical shaped bacteria. Isolated strains have been obtained from a variety of freshwaters and marine waters (Table 1). In addition, culture-independent studies revealed the presence of Spirochaeta species in other environments such as anaerobic bioreactors (Ariesyada et al., 2007), and the digestive tract of termites (Noda et al., 2003). A number of members of the genus Spirochaeta inhabit extreme environments with respect to temperature, salinity, and pressure (e.g., Hoover et al., 2003; Aksenova et al., 1992). These microorganisms may hence harbor enzymes with potential biotechnological applications.
Genome Structure
At present, a fully closed genome sequence of a member of Spirochaeta genus is not available. However, the genome size of three species of Spirochaeta are known.
1) Spirochaeta asiatica: 2100 Mb
2) Spirochaeta alkalica: 2700 Mb
3) Spirochaeta africana: 2500 Mb
Using HPLC(High Performance Liquid Chromatography), it was found that the DNA of Spirochaeta species have G+C contents ranging from 51-65 mol%.
Cell Structure, Metabolism and Life Cycle
The morphology and cellular structure of Spirochaeta spp. (and most other Spirochetes) is unique among prokaryotes. The cells are helical in shape and consist of an outer membrane, axial filaments (ultrastructurally similar to bacterial flagella), and a protoplasmic cylinder. The axial filaments reside under the outer membrane and are responsible for the unique mobility behavior of Spirochetes, a trait which has been linked to the pathogenicity of certain genera. Although the helical shape is typical for members of the Spirochetes phylum, a coccoid shaped Spirochaeta spp. was recently isolated from a termite gut by Droge et al. (2006).
The Spirochaeta genus contains a group a saccharolytic and dissipotrophic bacteria, responsible for decomposition of (poly)carbohydrates in many aquatic environments. All species of the Spirochaeta genus ferment carbohydrates with formation of acetate, ethanol, CO2, and H2 as major end products. In addition, Spirochaeta isovalerica ferments a number of amino-acids in addition to carbohydrates. All isolated Spirochaeta species utilize the Embden-Meyerhof pathway for glucose catabolization with formation of pyruvate.
Ecology and Applications
Species of the Spirochaeta genus are common inhabitants of a variety of aquatic environments, such as the water, sediments and muds of ponds, marshes, lakes, rivers and oceans. In these environments, Spirochaeta are capable of competing with other microorganisms for available nutrients by exhibiting various types of mobility behaviors. The unique mobility of Spirochetes is due to the helical shape of the cells and the polar positioning of the axial filaments.
It has also been known that one of its species, Spirocheata caldaria, probably forms symbiotic relationships with the bacteria, Clostridium thermocellum. Spirochaeta caldaria is a thermophilic spirochete taken from a freshwater hot spring. A study conducted by Pohlschroeder et al. showed that cellulose degradation is enhanced in Clostridium thermocellum when the spirochete is present within its environment.
Also, experiements have shown that some species of Spirochaeta could possibly be used in the direct bioconversion of cellulose-containing wastes to fuel such as ethanol or hydrogen gas.
References
Author
Page authored by Dieter Maurice Tourlousse and Godfrey Josef Torres, students of Prof. Jay Lennon at Michigan State University.
