Sphingomonadaceae
The Sphingomonadaceae form a family within the Alphaproteobacteria. The bacteria are found free in nature, eg in soil, marine or freshwater. An important feature is the presence of sphingolipids in the outer membrane of the cell walls. Sphingolipids are found in only a few groups of bacteria (such as in the Sphingobakterien ), among eukaryotes, but they are widespread. Especially in nervous tissue of mammals, they are important building blocks of cell membranes. Sphingomonadaceae are known also by their ability to reduce many different, sometimes toxic aromatics. This ability makes this interesting bacteria for soil remediation.
Features
The representatives are rod-shaped or ovoid. Some are pleomorphic, ie, the cells change shape over time or under different environmental conditions. Sphingomonadaceae not form spores ( asporogenous ) and are among the gram- negative bacteria. Some species are movable by means of flagella, the type Sphingomonas adhaesiva polar flagella is monotrich. Zymomonas unbegeißelt is usually, but also cells of one to four polar flagella occur. Apart from Zymomonas all species are obligately aerobic, they are not capable of living without oxygen. Zymomonas however, is facultative anaerobic to microaerophilic, growth is possible in environments with low amounts of oxygen or under completely anoxygenic conditions.
Metabolism
Except for Zymomonas is the oxidative metabolism (respiration). Zymomonas, however, fermented sugar (glucose ) to the alcohol (ethanol), the pathway is therefore the fermentation ( fermentation). The only way Zymomonas mobilis is used for the alcoholic fermentation of the juice of the agave Agave americana. The degradation pathway of sugar is not, as for example in the used for the brewery yeast glycolysis, but the Entner- Doudoroff pathway. In many types of Sphinomonadaceae various aromatics such as anthracene, serving as a sole carbon and energy source.
Many species are to carry out the oxidative photosynthetic able. You own the bacteriochlorophyll a and can photosynthesis used as complementary pathway, photosynthesis is not absolutely necessary for the growth and can not be used as the sole pathway ( photoorganotroph ). These include, for example Sandaracinobacter sibiricus, Sphingomonas ursincola and Sphingomonas natatoria (provided currently to Blastomonas natatoria ). Also in the phylogenetically related, counting on the same order family Erythrobacteraceae are photoorganotrophe species such B Erythrobacter, Erythromicrobium and Porphyrobacter, available.
Ecology
Sphingomonadaceae are widespread in the environment, which among other things, on its ability to utilize a wide range of carbon sources, is due. Many representatives of the Sphingomonadaceae were found in nutrient-poor environments, such as in sea water. Some species seem to play a key role in nutrient cycling and biomass production in oligotrophic ocean waters.
In nutrient-rich environments styles are available, Sphingomonas, Sphingobium and Novosphingobium were isolated from plant roots. Furthermore, species were found in blood samples. Since they are able to use various toxic to other organisms aromatic compounds as carbon source, they also come in polluted environments are relatively common. So Sphingopyxis was eg Sphingobium chlorophenolicum from a dirty floor with pentachlorophenol, isolated from an activated sludge.
Sphingolipids
Missing in some species in the outer membranes of the cell walls which are typical for Gram -negative bacteria lipopolysaccharides (LPS). Instead, certain sphingolipids, specifically various glycosphingolipids present. The glycosphingolipids replace the LPS and probably carry out similar functions was. The glycosphingolipid glucuronosyl ceramide occurs, for example in the cell walls of Sphingomonas and Zymomonas and is a key element for the classification of the genus. Also Galacturonosyl ceramide was detected in various types of Sphingomonas, such as Sphingopyxism terrae ( synonymous with Sphingomonas terrae, Sphingomonas wittichii and Sphingomonas yanoikuyae ). Glycosphingolipids were also found in the phylogenetically closely related, standing in the same order types of Erythrobacter, Erythromicrobium and Porphyrobacter. Except for the order Sphingomonadales sphingolipids were also detected in the bacterial genera Flectobacillus, Mycoplasma, Fusobacterium, Bacteroides and Flavobacterium. It is phylogenetically distant from each other standing groups, even for individual fungal species sphingolipids were found. Through the case of bacteria and fungi rare occurrence and phylogenetically widely dispersed situation of individual species makes the occurrence of sphingolipids for the taxonomy interesting.
Use
The Sphingomonadaceae, especially many kinds of the genus Sphingomonas, are able to use many different aromatic compounds as a sole carbon and energy source. This capability provides for example a way to detoxify contaminated soil ( soil remediation ) dar.
Toxic polychlorinated biphenyls can be decomposed, for example, on the kinds of Sphingomonas chlorophenolica and Sphingomonas paucimobilis. Sphingomonas paucimobilis is further capable of phenanthrene, fluoranthene, and various pesticides (eg lindane) degrade. The recently described species Novosphingobium naphthalenivorans is capable of reducing the environmentally harmful and health hazardous naphthalene. Further, some types of Sphingopyxism as p or p macrogoltabida terrae can (also known as Sphingomonas terrae ), for the degradation of polyethylene glycol (PEG), among others, a polyether -used as a binder or plasticizers, can be used.
Types of Sphingomonadaceae also be used in cosmetics and food industry. Sphingomonas paucimobilis is for example for the production of gellan, often referred to in this context as sphingan used. Gellan is used, inter alia, as a gelling agent for jams. In microbiology may be used as the Agarersatz Kultuvierung strains.
System
Some genera of this family are:
- Blastomonas Sly and Cahill 1997 emend. Hiraishi et al. 2000
- Citromicrobium Yurkov et al. 1999
- Lutibacterium Chung and King 2001
- Kaistobacter At D et al.
- Novosphingobium Takeuchi et al. 2001
- Sandaracinobacter Yurkov et al. 1997
- Sandarakinorhabdus Gich and Overmann 2006
- Sphingobium Takeuchi et al. 2001
- Sphingomonas Yabuuchi et al. 1990
- Sphingopyxis Takeuchi et al. 2001
- Sphingosinicella Maruyama et al. 2006 emend. Geueke et al. 2007
- Zymomonas Kluyver and van Niel 1936
The genus Sphingomonas, the type genus of the family Sphingomonadaceae was created by changes within the genus Pseudomonas. The system is partially under discussion, it was suggested that introduced by elimination of species of the genus Sphingomonas genera Sphingobium, Novosphingobium and Sphingopyxis attributed back to the original genus Spingomonas.