Rhodobacterales
The Rhodobacterales form an order within the Alphaproteobacteria. It consists of the families of the Rhodobacteraceae and Hyphomonadaceae. Like all Proteobacteria are gram- negative bacteria. Many Rhodobakterien have the ability to photosynthesize and are among the non- sulfur purple bacteria. Some representatives are able to use also the sulfur compounds as electron donors in the photosynthesis.
Characteristics and ecology
It is mostly rod -shaped bacteria, but also ovoid or coccoid bacteria (such Amaricoccus ) are included in this order. Even budding bacteria are present. In this particular type of cell division no binary fission takes place, instead of growing a daughter cell that is a time associated with the parent cell. The growth of the daughter cell is polar and does not, as is the case with the binary division, spread evenly over the cell body. Examples of budding bacteria of the Rhodobacteraceae are types of Gemmobacter and Rhodobacter blasticus well as types of Hirschia and Hyphomonas the Hyphomonadaceae.
Some species are motile by means of flagella, others are unbegeißelt. Some are strictly aerobic, others are facultative anaerobes and also show in oxygen-free environments growth. The latter include mainly the phototrophic species.
Members of the family Hyphomonadaceae occur in sea water, types of Rhodobacteraceae are also found in fresh water. Other habitats are land (eg Paracoccus ) and wastewater ( Amaricoccus ).
Metabolism
In the order of are phototrophic, but also chemoorganotrophic styles available. Some facultative anaerobic fermentation are capable of. Also Nitratatmer ( denitrifiers ) are present in the family, such as Paracoccus denitrificans and many types of Hyphomonas. These bacteria derive energy through the conversion of the nitrate ( NO3- ) bound nitrogen for a free, molecular nitrogen (N2).
Many types of Rhodobacterales among the non- sulfur purple bacteria. You are photoheterotroph. In Photohetertrophie light serves as an energy and organic substances as a carbon source. Photosynthesis is anoxygen, oxygen is not released here. Many types of Rhodobacteraceae, as well as other non- sulfur purple bacteria can also grow photoautotrophically, then carbon is obtained by fixing the inorganic CO2. Some make use of photosynthesis within certain sulfur compounds such as sulphide (S2 - ) or thiosulfate ( S2O32 - ) as electron donors. This feature is different than the name suggests, among the non- sulfur purple bacteria are not uncommon. Examples within the order are different types of Rhodobacter and Rhodovulum. All phototrophic species contain the bacteriochlorophyll a
System
A selection of the genera:
- Rhodobacteraceae Ahrensia
- Antarctobacter
- Methylarcula
- Oceanibulbus
- Palleronia
- Paracoccus
- Pseudovibrio
- Rhodobaca
- Rhodobacter
- Rhodovulum
- Sulfitobacter
- Yangia