Rhodococcus

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Rhodococcus
Rhodoccoccus sp.

Rhodoccoccus sp.

Systematics
Domain : Bacteria (bacteria)
Department : Actinobacteria
Order : Actinomycetales
Subordination : Corynebacterineae
Family : Nocardiaceae
Genre : Rhodococcus
Scientific name
Rhodococcus
Braid 1891

The genus Rhodococcus contains a variety of gram-positive , aerobic, acid-fast, rod-shaped bacteria species that live in the soil and are widespread. The genome for bacteria is exceptionally large.

features

Appearance

The cells of the species of Rhodococcus are gram-positive , sometimes also gram- variable. Short rod-shaped cells as well as branched filaments can be observed, as they are also found in other genera of the Actinomycetales (e.g. Amycolatopsis or Streptomyces ). The cells go through a development cycle, beginning with short rods or cocoid cells. These germinate into filamentous cell structures that - similar to the hyphae of fungi - can branch. The filaments and hyphae then fragment again, again clumsy rod-shaped cells are formed. In some bacterial strains , in addition to the substrate mycelium also an aerial mycelium is formed. Depending on the stage in the development cycle, the cells have an acid-resistant cell wall . As with the related genera Mycobacterium and Nocardia , this is due to the storage of mycolic acids in the bacterial cell wall .

The colonies are often colored, this is also noted in the genus name. Cream, yellow, orange, or red colonies appear in different strains. They can appear rough or smooth to slimy.

Growth and metabolism

All species of Rhodococcus are heterotrophic , they do not photosynthesize . They are strictly aerobic , i. H. dependent on oxygen. The catalase test is positive. Rhodococcus species can use numerous organic compounds for their metabolism and break them down. The temperatures for optimal growth are between 15 and 40 ° C for most trunks.

Chemotaxonomic Features

Structural formula of tuberculostearic acid , a branched- chain fatty acid that was first found in Mycobacterium tuberculosis , but is also found in the membrane lipids of Rhodococcus species.

The murein layer in the cell wall contains the diamino acid meso - diaminopimelic acid as a diagnostically important amino acid in the peptide bridge, as well as glutamic acid and alanine . The peptidoglycan type is A1γ. Diagnostically important sugars are arabinose and galactose . The main menaquinone is MK-8 (H 2 ). The phospholipids in the cell membrane consist mainly of diphosphatidylglycerol , phosphatidylethanolamine and phosphatidylinositol (the latter also associated with mannose ). A few typical fatty acids in the cell membrane cannot be determined. The fatty acid pattern contains larger amounts of saturated fatty acids such as C 16: 0 (hexadecanoic acid or palmitic acid ) and monounsaturated fatty acids such as C 18: 1  cis -9 (cis-9-octadecenoic acid or oleic acid ). Also branched-chain fatty acids are present, here is tuberculostearic (10-methyl-octadecanoic acid, C 18: 0  10-Me) a common representative.

The GC content in the bacterial DNA is 63 to 73 mol percent, which corresponds to the classification in the Actinobacteria division . The genome of the Rhodococcus sp. RHA1 (now assigned to the species Rhodococcus jostii ) was completely sequenced in 2006 . The genome comprises around 9.7 million base pairs , making it one of the largest bacterial genomes at all. The genome is packaged in a linear bacterial chromosome and three linear plasmids . Linear chromosomes are a rare feature in prokaryotes .

For phylogenetic studies, the nucleotides of the 16S rRNA, a typical representative of ribosomal RNA for prokaryotes, are determined . This is done in order to clarify the relationships between the microorganisms. In the case of Rhodococcus and Nocardia species, the mycolic acids present in the cell wall are also examined. In Rhodococcus species, the mycolic acids usually consist of 30–54 carbon atoms. Thus, Rhodococcus rhodochrous mycolic acids that are composed of a total of 38-46 carbon atoms in R. erythropolis the mycolic acids contain 34-40 carbon atoms and R. equi 30-36 C-atoms. The results of the investigations led to several Nocardia species now being included in the genus Rhodococcus .

Systematics

External system

The genus Rhodococcus in the family of the Nocardiaceae is placed to the subordination of the Corynebacterineae in the order of the Actinomycetales within the Phylum Actinobacteria. Since 2009, the extended family Nocardiaceae contains, in addition to Rhodococcus or Nocardia , other genera that were formerly part of the Gordoniaceae family, such as the genera Gordonia , Millisia and Skermania . Closely related genera (which are assigned to other families) are the Mycobacterium and Corynebacterium .

Internal system

So far (as of 2014) more than 40 species of Rhodococcus have been discovered. Rhodococcus rhodochrous is the type species of the genus, here is a selection of species:

Synonyms

The species Rhodococcus equi is often found under the name Corynebacterium equi , which is a basonym . Further synonyms for this type are u. a .: Nocardia restricta , Bacillus hoagii , Corynebacterium purulentus , Mycobacterium equi , Mycobacterium restrictum and Proactinomyces restrictus .

Rhodococcus bronchialis is now placed as Gordonia bronchialis , R. rubropertinctus as Gordonia rubripertincta and R. sputi as Gordonia sputi in the genus Gordonia . Also R. aurantiacus (now Tsukamurella paurometabola ) and R. chlorophenolicus (now Mycobacterium chlorophenolicum ) have been assigned to other genera.

etymology

The genus Rhodococcus was first described by Wilhelm Zopf in 1891 , he reported "on the excretion of fatty pigments (lipochromes) by certain fissile fungi". The generic name is made up of the Greek words rhodon ("rose") and kokkos ("berry") and means roughly "red coconut", and refers to the color of the colonies and the shape of the cells, these rather short rods than are real cocci.

Occurrence and meaning

Rhodococcus species are widespread and can be found in soil and water. They were isolated from soils of different geographic origins, ocean sediments and the excrement of herbivores, among other things . Some Rhodococcus strains are pathogens in humans and animals (especially horses), others are plant pathogenic ( R. fascians ).

The organism is able to convert polychlorinated biphenyls (PCB) and can thus live on contaminated soil. On a soil contaminated with lindane , Rhodococcus sp. RHA1 has been extracted. Tests with other Rhodococcus strains to break down environmentally persistent chemicals were also successful. The bacterial strains can break down vinyl chloride (VC) and trichlorethylene (TCE). Cell suspensions are used in a liquid nutrient medium that contains up to 40 mg / l vinyl chloride or 5 mg / l trichloroethene as additives that are broken down by the bacteria. Oxygen must be available for degradation. Other aliphatic and aromatic hydrocarbons, some of which are chlorinated , can also be used as a source of food by the Rhodococcus strains, including benzene , biphenyl and 1,1,1-trichloroethane . An industrial use of Rhodococcus takes place via the production of bioactive steroids , acrylamide and acrylic acid .

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literature

  • Michael Goodfellow, Peter Kämper, Hans-Jürgen Busse, Martha E. Trujillo, Ken-ichiro Suzuki, Wolfgang Ludwig, William B. Whitman (Eds.): Bergey's Manual of Systematic Bacteriology: Volume 5: The Actinobacteria . 2nd Edition. Springer-Verlag, New York 2012, ISBN 978-0-387-95043-3 , pp. 437-445 , doi : 10.1007 / 978-0-387-68233-4 .

Individual evidence

  1. ↑ a b c d e f g h i Amanda L. Jones, Michael Goodfellow: Genus VI. Rhodococcus . In: Bergey's Manual of Systematic Bacteriology: Volume 5: The Actinobacteria . 2nd Edition. Springer-Verlag, New York 2012, ISBN 978-0-387-95043-3 , pp. 437-445 .
  2. ↑ a b c F. A. Rainey, J. Burghardt u. a .: Polyphasic Evidence for the Transfer of Rhodococcus roseus to Rhodococcus rhodochrous. In: International Journal of Systematic Bacteriology. Volume 45, No. 1, January 1995, pp. 101-103, ISSN  0020-7713 . doi : 10.1099 / 00207713-45-1-101 .
  3. ↑ a b M. P. McLeod, RL Warren et al. a .: The complete genome of Rhodococcus sp. RHA1 provides insights into a catabolic powerhouse. In: Proceedings of the National Academy of Sciences . Volume 103, No. 42, October 2006, pp. 15582-15587, ISSN  0027-8424 . doi : 10.1073 / pnas.0607048103 . PMID 17030794 . PMC 1622865 (free full text).
  4. ^ Jean Euzéby, Aidan C. Parte: Phylum "Actinobacteria". In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Retrieved February 23, 2014 .
  5. ↑ XY Zhi, WJ Li, E. Stackebrandt: An update of the structure and 16S rRNA gene sequence-based definition of higher ranks of the class Actinobacteria, with the proposal of two new suborders and four new families and emended descriptions of the existing higher taxa. In: International journal of systematic and evolutionary microbiology. Volume 59, No. 3, March 2009, pp. 589-608, ISSN  1466-5026 . doi : 10.1099 / ijs.0.65780-0 . PMID 19244447 .
  6. ↑ a b c Jean Euzéby, Aidan C. Parte: Genus Rhodococcus. In: List of Prokaryotic names with Standing in Nomenclature ( LPSN ). Retrieved February 23, 2014 .
  7. ^ Prokaryotic Nomenclature Up-to-date. In: Website of the Leibniz Institute DSMZ - German Collection of Microorganisms and Cell Cultures GmbH . Retrieved December 23, 2013 .
  8. ^ S. Klatte, K.-D. Jahnke u. a .: Rhodococcus luteus Is a Later Subjective Synonym of Rhodococcus fascians. In: International Journal of Systematic Bacteriology. Vol. 44, No. 4, October 1994, pp. 627-630, ISSN  0020-7713 . doi : 10.1099 / 00207713-44-4-627 .
  9. ↑ KJ Malachowsky, TJ Phelps et al. a .: Aerobic mineralization of trichlorethylene, vinyl chloride, and aromatic compounds by rhodococcus species. In: Applied and environmental microbiology. Vol. 60, No. 2, February 1994, pp. 542-548, ISSN  0099-2240 . PMID 16349184 . PMC 201346 (free full text).

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