Role of IncP-1 Plasmids pWDL7::rfp and pNB8c in Chloroaniline Catabolism as Determined by Genomic and Functional Analyses

Department of Biological Sciences, Institute for Bioinformatics and Evolutionary Studies, University of Idaho, Moscow, Idaho, USA.
Applied and Environmental Microbiology (Impact Factor: 3.67). 11/2011; 78(3):828-38. DOI: 10.1128/AEM.07480-11
Source: PubMed


Broad-host-range catabolic plasmids play an important role in bacterial degradation of man-made compounds. To gain insight
into the role of these plasmids in chloroaniline degradation, we determined the first complete nucleotide sequences of an
IncP-1 chloroaniline degradation plasmid, pWDL7::rfp and its close relative pNB8c, as well as the expression pattern, function, and bioaugmentation potential of the putative
3-chloroaniline (3-CA) oxidation genes. Based on phylogenetic analysis of backbone proteins, both plasmids are members of
a distinct clade within the IncP-1β subgroup. The plasmids are almost identical, but whereas pWDL7::rfp carries a duplicate inverted catabolic transposon, Tn6063, containing a putative 3-CA oxidation gene cluster, dcaQTA1A2BR, pNB8c contains only a single copy of the transposon. No genes for an aromatic ring cleavage pathway were detected on either
plasmid, suggesting that only the upper 3-CA degradation pathway was present. The dcaA1A2B gene products expressed from a high-copy-number vector were shown to convert 3-CA to 4-chlorocatechol in Escherichia coli. Slight differences in the dca promoter region between the plasmids and lack of induction of transcription of the pNB8c dca genes by 3-CA may explain previous findings that pNB8C does not confer 3-CA transformation. Bioaugmentation of activated
sludge with pWDL7::rfp accelerated removal of 3-CA, but only in the presence of an additional carbon source. Successful bioaugmentation requires
complementation of the upper pathway genes with chlorocatechol cleavage genes in indigenous bacteria. The genome sequences
of these plasmids thus help explain the molecular basis of their catabolic activities.

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    • "Similarly, C. testosteroni 12 metabolizes 3-chloroaniline via the meta-cleavage pathway (Boon et al., 2000). Król et al. (2012) showed that chloroaniline dioxygenase of C. testosteroni WDL7 is a multicomponent enzyme consisting of large and small subunits of dioxygenase (encoded by dcaA1, dcaA2), and a reductase (encoded by dcaA3). "
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