Degradation of trichloroethene by a linear-plasmid-encoded alkene monooxygenase in Rhodococcus corallinus (Nocardia corallina) B-276

Abstract

Rhodococcus corallinus (formerly Nocardia corallina) 6-276, isolated with propene as sole carbon and energy source, is able to oxidize trichloroethene (TCE). Glucose-or propene-grown R. corallinus B-276 cells exhibited no difference in TCE degradation efficiency. TCE degradation was found to be growth-phase-dependent and maximum rates were monitored with stationaryphase cells. K,,, and V,,, values for TCE degradation of R. corallinus 6-276 grown in nutrient broth medium in the presence of glucose were 187 pM and 2-4 nmol min" (mg protein)", respectively. fscherichia coli recombinants harbouring and expressing the alkene monooxygenase genes of R. corallinus B-276 exhibited the ability to degrade TCE. This result provides clear evidence that the alkene monooxygenase of R. corallinus B-276 catalyses TCE oxidation. R. corallinus B-276 was shown to contain four linear plasmids, pNCIO (70 kb), pNC20 (85 kb), pNC30 (185 kb) and pNC4O (235 kb). The observation that pNC30-deficient strains had lost the ability to grow on propene suggested that the genes of the propene degradation pathway are encoded by the linear plasmid pNC30. Southern blot analysis with cloned alkene monooxygenase genes from R. corallinus B-276 revealed a positive hybridization signal with the linear plasmid pNC30. This result clearly shows that the alkene monooxygenase is encoded by the linear plasmid pNC30. Eleven short-chainalkene-oxidizing strains were screened for the presence of linear plasmids. Among these, four propene-oxidizing Rhodococcus strains and one etheneoxidizing Mycobacterium strain were found to contain linear megaplasmids. Southern blot analysis with the alkene monooxygenase revealed positive signals with linear plasmids of two propene-oxidizing Rhodococcus ruber strains. These results indicate that homologous alkene monooxygenases are encoded by linear plasmids in R. ruber strains.

Distribution of the Coenzyme M Pathway of Epoxide Metabolism among Ethene- and Vinyl Chloride-Degrading Mycobacterium Strains

“…In addition to unique biochemical reactions, the propene assimilation pathway is also distinguished by unusual genetic elements. In both strains Py2 and B-276, the propene monooxygenase genes are carried on linear megaplasmids, and in strain Py2, the epoxide carboxylase system and CoM biosynthesis genes are also plasmid borne (18,26).As part of the study that yielded strain JS60, we isolated many other mycobacteria that grew on VC (5). It is not known whether these isolates or similar Mycobacterium strains isolated on ethene (6, 7) possess EaCoMT enzymes.…”

A linear megaplasmid, p1CP, carrying the genes for chlorocatechol catabolism of Rhodococcus opacus 1CP

“…Rhodococcus corallinus B-276 was even found to harbour four linear plasmids, pNC10 (70 kb), pNC20 (85 kb), pNC30 (185 kb) and pNC40 (235 kb). The gene for an alkene monooxygenase, which allows this organism to grow on propene and to co-oxidize trichloroethene, was shown to be located on pNC30 (Saeki et al, 1999). In contrast, only single linear plasmids, pBD2 (210 kb) and pTA421 (500 kb), were detected in the isopropylbenzene-degrading strain R. erythropolis BD2 (Kesseler et al, 1996;Stecker et al, 2003) and the (chloro)biphenyl degrader R. erythropolis TA421 (Kosono et al, 1997), respectively.…”

“…Plasmids of rhodococci, which, like their Streptomyces counterparts often possess linear topology, frequently encode catabolic genes, enabling their hosts either to grow with unusual carbon and energy sources such as CO 2 / hydrogen (Kalkus et al, 1990), (chloro)biphenyl (Kosono et al, 1997;Masai et al, 1997), and isopropylbenzene (Dabrock et al, 1994;Stecker et al, 2003) or to just convert such compounds as was shown for trichloroethene (Dabrock et al, 1994;Saeki et al, 1999). In addition, linear plasmids of rhodococci were shown to harbour genes for resistance to thallium (Kalkus et al, 1990) and arsenic (Dabrock et al, 1994;Stecker et al, 2003), as well as genes for phytopathogenicity (Maes et al, 2001).…”

Monooxygenases involved in the n-alkanes metabolism by Rhodococcus sp. BCP1: molecular characterization and expression of alkB gene

“…Indeed, the broad substrate range [148] allows them to oxidize a variety of halogenated-alkanes, alkenes and aromatics with favourable kinetic parameters [13] and (in some cases) stereo-selectivity [149]. All SDIMO groups so far examined include enzymes capable of co-metabolically oxidizing halogenated pollutants such as trichloroethene (TCE) and vinyl chloride (VC) [150][151][152][153]. Some members showed also the ability to co-metabolize methyl tert-butyl ether (MTBE) [67].…”