Rhodococcus
Rhodoccoccus sp.
The genus Rhodococcus contains a variety of gram-positive, aerobic, acid-fast, rod- shaped bacteria that live in soil and are widely used. The genome is unusually large for bacteria.
- 2.1 Outer systematics
- 2.2 Internal systematics
- 2.3 Synonyms
- 2.4 Etymology
- 4.1 Literature
- 4.2 Notes and references
Features
Appearance
The cells of the Rhodococcus species are gram- positive, gram sometimes variable. It can be observed a short rod-shaped cells, but also branched filaments, as they occur (for example, Amycolatopsis or Streptomyces ) and other genera of the Actinomycetales. The cells go through a development cycle, starting with short rods or coccoid cells. These germinate to filamentous cell structures, which - similar to the hyphae of fungi - can branch. The filaments and hyphae then fragment again, this clumsy rod-shaped cells are formed again. In some bacterial strains also a aerial mycelium is formed adjacent the substrate mycelium. Depending on the section of the development cycle, the cells have an acid-fast cell wall. This is - as in the related genera Mycobacterium and Nocardia - founded by the incorporation of mycolic acids in the bacterial cell wall.
The colonies are often colored, this is noted in the genus name. In various strains occur off-white, yellow, orange or red colonies. They may appear rough or smooth to slimy.
Growth and metabolism
All kinds of Rhodococcus are heterotrophic, they do not perform photosynthesis. They are strictly aerobic, that is dependent on oxygen. The catalase test is positive. Rhodococcus species may use many organic compounds for their metabolism and degrade them. The temperatures for optimal growth for most strains are between 15 and 40 ° C.
Chemotaxonomic features
The murein layer of the cell wall containing the diamino acid meso -diaminopimelic acid as diagnostically important amino acid in the peptide bridge, and also glutamic acid or alanine. The peptidoglycan type is A1γ. Diagnostically important sugars are arabinose and galactose. The major menaquinone is MK -8 ( H2). The phospholipids in the cell membrane composed mainly of diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol (the latter also associated with mannose ). A few typical fatty acids in the cell membrane can not be fixed. The fatty acid pattern contains large amounts of saturated fatty acids such as C16: 0 ( palmitic or hexadecanoic acid ) and monounsaturated fatty acids, such as C18: 1 cis -9 ( cis-9- octadecenoic acid and oleic acid). And branched chain fatty acids are found, here is the Tuberkulostearinsäure (10 -methyl- octadecanoic acid, C18: 0 10 - Me), a common representative.
The GC content in the bacterial DNA is 63 to 73 mole percent, which corresponds to the position in the Department of Actinobacteria. The genome of Rhodococcus sp. RHA1 ( now the type Rhodococcus jostii assigned ) in 2006 was already fully sequenced. The genome comprises about 9.7 million base pairs and thus is regarded as one of the largest bacterial genomes at all. Packed is the genome in a linear bacterial chromosome and three linear plasmids. Linear chromosomes are a rare feature in prokaryotes.
For phylogenetic analyzes of the 16S rRNA nucleotides are determined, a typical representative for prokaryotes the ribosomal RNA. This is done in order to clarify the phylogenetic relationships of microorganisms with each other. In Rhodococcus, as with Nocardia species additionally present in the cell wall of mycolic acids are still under investigation. Rhodococcus species in the mycolic acids usually comprise 30 to 54 carbon atoms. To Rhodococcus rhodochrous has mycolic acids, which is exclusively composed of 38-46 carbon atoms in R. erythropolis the mycolic acids contain 34-40 carbon atoms and at R. equi 30-36 carbon atoms. The results of the investigations led to several Nocardia species are now in genus Rhodococcus.
System
Outer systematics
The genus Rhodococcus in the family of Nocardiaceae will be provided to the subordination of Corynebacterineae in the order of Actinomycetales within the phylum Actinobacteria. Since 2009, the extended family Nocardiaceae contains Rhodococcus or Nocardia further genera of the family Gordoniaceae were attributed to earlier, such as the genera Gordonia, Millisia and Skermania. Closely related genera ( but other families are assigned ) are Mycobacterium and Corynebacterium.
Inside systematics
So far (as of 2014) are more than 40 species have been discovered by Rhodococcus. Rhodococcus rhodochrous is the type species of the genus, a selection of ways:
- Rhodococcus aetherivorans Goodfellow et al. 2004
- Rhodococcus artemisiae Zhao et al. 2012
- Rhodococcus baikonurensis Li et al. 2004
- Rhodococcus cerastii fighters et al. 2013
- Rhodococcus coprophilus Rowbotham & Cross 1979
- Rhodococcus corynebacterioides (. Serrano et al 1972) Yassin & Schaal 2005 ( synonym: Nocardia corynebacterioides Serrano et al 1972. )
- Rhodococcus equi ( Magnusson 1923) Goodfellow and Alderson 1977 ( Basonym: Corynebacterium equi Magnusson 1923); most important species for infections in animals (horse, goat) and immunosuppressed people (AIDS -infected )
- Rhodococcus erythropolis ( Gray & Thornton 1928) Goodfellow and Alderson 1979
- Rhodococcus fascians ( Tilford 1936) Goodfellow 1984 ( synonym: Rhodococcus luteus (ex Söhngen 1913) Nesterenko et al 1982. )
- Rhodococcus globerulus Goodfellow et al. 1985
- Rhodococcus gordoniae Jones et al. 2004
- Rhodococcus imtechensis Ghosh et al. 2006
- Rhodococcus jostii Takeuchi et al. 2002; to this type of 2006 was discovered Rhodococcus sp. asked RHA1
- Rhodococcus koreensis Yoon et al. 2000
- Rhodococcus kroppenstedtii Mayilraj et al. 2006
- Rhodococcus maanshanensis Zhang et al. 2002
- Rhodococcus marinonascens Helmke & Weyland 1984
- Rhodococcus opacus Klatte et al. 1995
- Rhodococcus percolatus Briglia et al. 1996
- Rhodococcus phenolicus Rehfuss and Urban 2006
- Rhodococcus pyridinivorans Yoon et al. 2000
- Rhodococcus qingshengii Xu et al. 2007
- Rhodococcus rhodnii Goodfellow & Alderson 1979
- Rhodococcus rhodochrous ( Zopf 1891) Tsukamura 1974 emend. Rainey et al. 1995 ( type species, synonym: Rhodococcus roseus (ex Grotenfelt 1889) Tsukamura et al 1991. )
- Rhodococcus ruber ( Kruse 1896) Goodfellow and Alderson 1977 ( synonym: Nocardia pellegrino )
- Rhodococcus triatomae Yassin 2005
- Rhodococcus trifolii fighters et al. 2013
- Rhodococcus tukisamuensis Matsuyama et al. 2003
- Wratislaviensis Rhodococcus ( Goodfellow et al., 1995) Goodfellow et al. 2002 ( Basonym: Tsukamurella wratislaviensis Goodfellow et al 1995. )
- Rhodococcus yunnanensis Zhang et al. 2005
Synonyms
The type Rhodococcus equi is often found under the name Corynebacterium equi, which is considered Basonym. Are more synonyms for this type including the following: restricta Nocardia, Bacillus hoagii, Corynebacterium purulentus, Mycobacterium equi, Mycobacterium restrictum and Proactinomyces restrictus.
Rhodococcus bronchialis is now provided as Gordonia bronchialis, R. rubropertinctus as Gordonia rubripertincta and R. Sputi as Gordonia Sputi to the genus Gordonia. Also R. aurantiacus ( now Tsukamurella paurometabola ) and R. chlorophenolicus ( now Mycobacterium chlorophenolicum ) were assigned to other genera.
Etymology
The genus Rhodococcus was first described in 1891 by Wilhelm Zopf, he reported " on excretion of fat dyes ( Lipochromen ) by certain fungi gap ". The genus name is derived from the Greek words rhodon ( "Rose" ) and kókkos ( " berry " ) together and means " red coccus ", and refers to the color of the colonies and the shape of the cells, this rather short rods are as real cocci.
Occurrence and significance
Rhodococcus species are widespread and found in the soil and water. And have been isolated from soil, among other different origin, ocean sediment, and the feces of herbivores. Some Rhodococcus strains are pathogens in humans and animals ( esp. horses), others are phytopathogenic (R. fascians ).
The organism is capable of polychlorinated biphenyls ( PCBs) and can convert to live on contaminated soils. On a contaminated soil with lindane Rhodococcus sp is. Been extracted RHA1. Experiments with other Rhodococcus strains with regard to the reduction umweltpersistenter chemicals were successful. The bacterial strains, vinyl chloride ( VC) and trichloroethene (TCE ) degrade. In this case, the cell suspensions can be used in a liquid nutrient medium containing up to 40 mg / l of vinyl chloride and 5 mg / l of trichlorethylene as additives, which are degraded by the bacteria. For the reduction of oxygen must be available. Also aliphatic and aromatic hydrocarbons, also partially chlorinated, can be used by Rhodococcus strains as a food source, such as benzene, biphenyl, and 1,1,1- trichloroethane. Industrial use of Rhodococcus via the preparation of bioactive steroids, acrylamide and acrylic acid.