Rhodococcus Wratislaviensis Research Articles

Rhodococcus imtechensis sp. nov., a nitrophenol-degrading actinomycete

A Gram-positive actinobacterium, strain RKJ300(T), capable of utilizing p-nitrophenol and 2,4-dinitrophenol, was isolated from a pesticide-contaminated site in India. The morphological and chemotaxonomic properties of the isolate were typical of members of the genus Rhodococcus. The DNA G+C content was 72 mol%. Strain RKJ300(T) exhibited the highest level of sequence similarity with Rhodococcus wratislaviensis NCIMB 13082(T) (99.3 %), followed by Rhodococcus opacus DSM 43205(T) (98.8 %), Rhodococcus percolatus MBS1(T) (98.6 %) and Rhodococcus koreensis DNP505(T) (98.1 %). The low levels of DNA-DNA relatedness (49-58 %) with the above micro-organisms, and the differences in the biochemical and physiological properties, suggest that strain RKJ300(T) should be classified within a novel species of the genus Rhodococcus, for which the name Rhodococcus imtechensis sp. nov. is proposed. The type strain is RKJ300(T) (=MTCC 7085(T)=JCM 13270(T)).

Characterization of selected actinomycetes degrading polyaromatic hydrocarbons in liquid culture and spiked soil

Five strains of the Rhodococcus and Gordonia genera were evaluated for their potential use in bioremediation of polycyclic aromatic hydrocarbons (PAH) with or without another substrate (co-substrate). Their ability to produce biosurfactants or to degrade phenanthrene when growing on glucose, hexadecane and rapeseed oil was tested in liquid medium at 30 °C. All strains showed biosurfactant activity. The highest reduction in surface tension was recorded in whole cultures of Rhodococcus sp. DSM 44126 (23.1%) and R. erythropolis DSM 1069 (21.1%) grown on hexadecane and Gordonia sp. APB (20.4%) and R. erythropolis TA57 (18.2%) grown on rapeseed oil. Cultures of Gordonia sp. APB and G. rubripertincta formed emulsions when grown on rapeseed oil. After 14 days of incubation, Rhodococcus sp. DSM 44126 degraded phenanthrene (initial concentration 100 μg ml−1) as sole carbon source (79.4%) and in the presence of hexadecane (80.6%), rapeseed oil (96.8%) and glucose (below the limit of detection). The other strains degraded less than 20%, and then with a co-substrate only. Rhodococcus sp. DSM 44126 was selected and its performance evaluated in soil spiked with a mixture of PAH (200 mg kg−1). The effect of the addition of 0, 0.1 and 1% rapeseed oil as co-substrate was also tested. Inoculation enhanced the degradation of phenanthrene (55.7% and 95.2% with 0.1% oil and without oil respectively) and of anthracene (29.2% with 0.1% oil). Approximately 96% of anthracene and 62% of benzo(a)pyrene disappeared from the soil (inoculated and control) after 14 days and anthraquinone was detected as a metabolite. Rhodococcus sp. DSM 44126 was identified as Rhodococcus wratislaviensis by 16S rRNA sequencing and was able to degrade anthracene as sole carbon source in liquid culture.

Characterization of Rhodococcus wratislaviensis strain J3 that degrades 4-nitrocatechol and other nitroaromatic compounds

The bacterial strain J3 was isolated from soil by selective enrichment on mineral medium containing 4-nitrocatechol as the sole carbon and energy source. This strain was identified as Rhodococcus wratislaviensis on the basis of morphology, biochemical, physiological and chemotaxonomic characterization and complete sequencing of the 16S rDNA gene. The isolated bacterium could utilize 4-nitrocatechol, 3-nitrophenol and 5-nitroguaiacol as sole carbon and energy sources. Stoichiometric release of nitrites was measured during degradation of 4-nitrocatechol both in growing cultures and for stationary phase cells. The J3 strain was unable to degrade 4-nitroguaiacol, 2-nitrophenol, 4-nitrophenol, 2,4-dinitrobenzoic acid, 4,5-dimethoxy-2-nitrobenzoic acid and 2,3-difluoro-6-nitrophenol. The J3 strain is deposited in the Czech Collection of Microorganisms as CCM 4930.

Biodegradation and detoxification of -nitrophenol by Rhodococcus wratislaviensis

An indigenous bacterial strain capable of utilizing p-nitrophenol (PNP) as the sole carbon, nitrogen and energy source was isolated from a river sediment in Buenos Aires (Argentina). The 16S rDNA sequence showed a close relationship to Rhodococcus wratislaviensis. This indigenous bacterial strain degrades 0.36 and 0.72 mM PNP in 34 and 56 h, respectively, and releases the nitro group from the compound as nitrite. Aerobic biodegradation assays were performed using a 2-L microfermentor at 28∘C with agitation (200 rpm). Biodegradation was evaluated by spectrophotometry, gas chromatography and microbial growth. As the nitrite released during PNP degradation is also an environmental toxic agent it was removed by adding a denitrification step in an anoxic process. Detoxification was evaluated by using a Daphnia magna toxicity test. Toxicity was not detected after the combination of both, an aerobic biodegradation test and denitrification in an anoxic process.

Transfer of Tsukamurella wratislaviensis Goodfellow et a. 1995 to the genus Rhodococcus as Rhodococcus wratislaviensis comb. nov..

A polyphasic study was undertaken to clarify the taxonomic position of the type strain (N805T) of Tsukamurella wratislaviensis. This organism showed a combination of phenotypic properties, notably chemotaxonomic markers, consistent with its classification in the genus Rhodococcus. Comparative 16S rDNA sequencing studies indicated that strain 805T falls into the Rhodococcus erythropolis subclade, where it forms a monophyletic group with the type strains of Rhodococcus opacus and Rhodococcus percolatus. The close relationship between these strains was underpinned by the results of mycolic acid analyses. However, strain N805T was distinguished from the R. opacus and R. percolatus strains in DNA-DNA pairing experiments and by using a range of phenotypic properties. In light of these studies, it is clear that strain N805T is misclassified in the genus Tsukamurella. It is, therefore, proposed that Tsukamurella wratislaviensis Goodfellow et al. 1995 be transferred to the genus Rhodococcus as Rhodococcus wratislaviensis comb. nov..