Rhodococcus
Classification
Bacteria; Actinobacteria; Actinobacteria (class); Actinobacteridae; Actinomycetales; Corynebacterineae; Nocardiaceae; Rhodococcus
Species
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NCBI: Taxonomy |
Genus species
Description and Significance
Rhodococcus is a genus of non-motile, non-sporulating, aerobic gram-positive filamentous rods of the phylum Actinobacteria (1). These organisms reside in soil and water environments and are classified as one of the most industrial important organisms. Studies have shown these organisms to grow in both mesophilic (2) and psychrophilic (3) conditions. Strains of Rhodococcus contain enzymes that carry out biologically relevant reactions such as biodesulfurization of fossil fuels, degradation of polychlorinated biphenyls (PCBs), and utilization of a wide variety of other organic compounds as energy sources (2). Therefore, Rhodococcus plays an important role in the global recycling of carbon. Additionally, Rhododcoccus is used commercially as a biocatalyst in the production of fossil fuels, bioactive steroids, and acrylamide (1). The production of dioxygenases by Rhodococcus for the degradation of PCBs has become increasingly important to researchers, as they search for a method to degrade the biologically toxic compounds. Additionally, the ability of Rhodococcus to be used in bioremediaion may be essential in decontaminating polluted land and waterways throughout the United States.
Genome Structure
The genome of Rhodococcus sp. RHA1, a biphenyl degrading strain, is one of the largest geonomes to date that has been sequenced. It contains a linear chromosome and three linear plasmids totaling 9.7 kb and is 67% G-C base pairs. Within the genome, there are a predicted 9,145 genes. These genes encode 1,578 proteins belonging to known protein families, 2,538 hypothetical proteins, and 3,511 proteins of unknown function (1).
It is believed the linear conformation of the plasmid within Rhodococcus was acquired via bacteriophages (2). The three plasmids contain 11 genes which produce proteins necessary for the catabolism of aromatic molecules (1). The linear nature of the chromosome is hypothesized to have formed following recombination between a circular chromosome and linear plasmids (2).
Rhodococcus sp. RHA1 encodes for a total of 1,085 oxidoreductases and 192 ligases, which is abundant when compared to other Actinomycetes. The catabolic nature of oxygenases are utilized in hydroxylation of aromatic compounds, necessary for degradation (2). Of the oxidases encoded in the genome of Rhodococcus, 77% reside within the chromosome. Horizontal gene transfer is thought to comprise 7% of the oxygenases of Rhodococcus. Therefore, it is believed RHA1 has a fundamental aspect which requires it to carry out PCB degradation (1).
The diverse ability of Rhodococcus to carry out catabolic activities of aromatic compounds is believed to have been acquired through ancient horizontal gene transfer acquisitions. Following duplications within the genome the organism acquired the vast numeral abundance presented in genomic studies. However, due to few transposases, one psuedogene, and only to insertion sequences (IS), it is hypothesized Rhodococcus is a relatively stable genome and has experienced little genetic change recently (1).
Cell Structure, Metabolism and Life Cycle
Interesting features of cell structure; how it gains energy; what important molecules it produces.
Ecology and Pathogenesis
Habitat; symbiosis; biogeochemical significance; contributions to environment.
If relevant, how does this organism cause disease? Human, animal, plant hosts? Virulence factors, as well as patient symptoms.
References
1. McLeod, M. et. al. "The complete genome of Rhodococcus sp. RHA1 provides insights into a catabolic powerhouse". Preceeding of the National Academy of Sciences. 2006. Volume 103. p. 15582-15587.
2. Meijer, G. W. and John F. Prescott "Rhodococcus equi". Veterinary Research-A Journal on Animal Infection and Epidemiology. 2004. Volume 35. p. 383-396.
3. Warren, R. et. al. "Functional Characterization of a Catabolic Plasmid from Polychlorinated Biphenyl Degrading Rhodococcus sp. Strain RHA1". Journal of Bacteriology. 2004. Volume 186. p. 7783-7795.
4. Whyte, L. et. al. "Biodegradation of Variable-Chain-Length Alkanes at Low Temperatures by a Psychrotrophic Rhodococcus sp.". Applied and Environmental Microbiology. 1998. Volume 64. p. 2578-2584.
Author
Page authored by Bruce Fraser & Hermes Fernandez, students of Prof. Jay Lennon at Michigan State University.
