Planctomycetes
The Planctomycetes or Planctomycetes form a well- marginated phylum within the domain of the bacteria. They were discovered in the 1970s. Since then it has planctomycetes almost everywhere able to identify in the environment. Many species of aquatic, both in salt as in fresh water. Some occur in hypersaline ( highly saline ) water, others in soil or sewage sludge. The most important genera are Planctomyces, Pirellula, Isosphaera and Gemmata.
Features
The Planctomycetes are unique in several ways. The cells are extremely strong Planctomyces compartmentalized and often have - like the eukaryotes - a membrane surrounding the DNA. The cells are stalked and show a dimorphic life cycle that is known is also of Caulobacter, a type of alpha -proteobacteria: a sessile cell constricted from a daughter cell that forms a flagellum at the opposite pole. This swarm cell is mobile, the Scourge raises but off after some time and now forms part, a handle with which it attaches itself to a solid surface. The stem of Planctomyces cells is structured differently than that of Caulobacter, both genera are not related.
Planctomycetes are also unusual because their cell wall has no murein, but consists of a protein S-layer.
The bacteria live chemoorganotroph and are facultative aerobic, besides stalked exist filamentous forms. So the kind Isosphaera pallida is a filamentous to slidably Locomotive bacterium that is common in hot springs at temperatures between 35 and 55 ° C.
Ecology
Some Planctomycetes form associations with animals, such as Insects. Some unidentified Planctomycetes were found by means of 16S rRNA analysis in digestive tracts of termites Cubitermes ugandensis and Cubitermes orthognathus. A Planktomycet probably the genus Pirellula was found in the water flea Daphnia pulex. Another type was isolated from Penaeus monodon shrimp. Also in the sponges Aplysina cavernicola and Aplysina aerophoba Planctomycetes were detected.
In which connection the bacteria with the hosts stand ( symbiosis or parasitism ) and what function they perform in the digestive tract, is still unclear.
System
Analyzes of 16S rRNA gene sequences and other studies have shown a close relationship of the Planctomycetes and Verrucomicrobia and Chlamydiae the departments of. As a result, they form the so-called PVC Superphylum.
Genera:
- Blastopirellula Schlesner et al. 2004
- Gemmata Franzmann & Skerman 1985
- Isosphaera Giovannoni et al. 1995
- Pirellula Schlesner & Hirsch 1987
- Planctomyces Gimesi 1924
- Rhodopirellula Schlesner et al. 2004
- Candidatus Jettenia
- Candidatus Scalindua