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Insights into functional and evolutionary analysis of carbaryl metabolic pathway from Pseudomonas sp. strain C5pp.

ABSTRACT: Carbaryl (1-naphthyl N-methylcarbamate) is a most widely used carbamate pesticide in the agriculture field. Soil isolate, Pseudomonas sp. strain C5pp mineralizes carbaryl via 1-naphthol, salicylate and gentisate, however the genetic organization and evolutionary events of acquisition and assembly of pathway have not yet been studied. The draft genome analysis of strain C5pp reveals that the carbaryl catabolic genes are organized into three putative operons, 'upper', 'middle' and 'lower'. The sequence and functional analysis led to identification of new genes encoding: i) hitherto unidentified 1-naphthol 2-hydroxylase, sharing a common ancestry with 2,4-dichlorophenol monooxygenase; ii) carbaryl hydrolase, a member of a new family of esterase; and iii) 1,2-dihydroxy naphthalene dioxygenase, uncharacterized type-II extradiol dioxygenase. The 'upper' pathway genes were present as a part of a integron while the 'middle' and 'lower' pathway genes were present as two distinct class-I composite transposons. These findings suggest the role of horizontal gene transfer event(s) in the acquisition and evolution of the carbaryl degradation pathway in strain C5pp. The study presents an example of assembly of degradation pathway for carbaryl.

SUBMITTER: Trivedi VD

PROVIDER: S-EPMC5141477 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Insights into functional and evolutionary analysis of carbaryl metabolic pathway from Pseudomonas sp. strain C5pp.

Trivedi Vikas D VD Jangir Pramod Kumar PK Sharma Rakesh R Phale Prashant S PS

Scientific reports 20161207

Carbaryl (1-naphthyl N-methylcarbamate) is a most widely used carbamate pesticide in the agriculture field. Soil isolate, Pseudomonas sp. strain C5pp mineralizes carbaryl via 1-naphthol, salicylate and gentisate, however the genetic organization and evolutionary events of acquisition and assembly of pathway have not yet been studied. The draft genome analysis of strain C5pp reveals that the carbaryl catabolic genes are organized into three putative operons, 'upper', 'middle' and 'lower'. The seq ...[more]

PMID: 27924916

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Project description:Carbaryl is the most widely used carbamate family pesticide, and its persistent nature causes it to pollute both soil and water ecosystems. Microbes maintain the Earth's biogeochemical cycles by metabolizing various compounds present in the matter, including xenobiotics, as a sole source of carbon, nitrogen, and energy. Soil isolate Pseudomonas sp. strain C5pp metabolizes carbaryl efficiently as the carbon source. Periplasmic carbaryl hydrolase catalyzes the conversion of carbaryl to 1-naphthol and methylamine. 1-Naphthol was further used as a carbon source via gentisate, whereas the metabolic fate of methylamine is not known. Here, we demonstrate that strain C5pp showed efficient growth on carbaryl when supplied as a carbon and nitrogen source, suggesting that the methylamine generated was used as the nitrogen source. Genes involved in the methylamine metabolism were annotated and characterized at the biochemical and molecular level. Transcriptional and enzyme activity studies corroborate that the ?-glutamylmethylamide/N-methylglutamate (GMA/NMG) pathway is involved in the metabolism of carbaryl and methylamine as a nitrogen source. Compared to carbaryl, methylamine was found to be an effective inducer for the metabolic and transporter genes. Strain C5pp also harbored genes involved in sarcosine metabolism that were cotranscribed and induced by sarcosine. The presence of inducible pathways for metabolism of carbaryl as a nitrogen and carbon source helps in complete and efficient mineralization of carbaryl by strain C5pp, thereby maintaining the biogeochemical cycles.IMPORTANCE The degradation of xenobiotics plays a significant role in the environment to maintain ecological systems as well as to prevent the imbalance of biogeochemical cycles via carbon-nitrogen cycling. Carbaryl is the most widely used pesticide from the carbamate family. Pseudomonas sp. strain C5pp, capable of utilizing carbaryl as a carbon and nitrogen source for its growth, subsequently helps in complete remediation of carbaryl. Thus, it maintains the ecosystem by balancing the biogeochemical cycles. The metabolic versatility and genetic diversity of strain C5pp for the transformation of contaminants like carbaryl and 1-naphthol into less harmful products make it a suitable candidate from the perspective of bioremediation.

Project description:Although enzyme-encoding genes involved in the degradation of carbaryl have been reported in Pseudomonas sp. strain XWY-1, no regulator has been identified yet. In the mcbABCDEF cluster responsible for the upstream pathway of carbaryl degradation (from carbaryl to salicylate), the mcbA gene is constitutively expressed, while mcbBCDEF is induced by 1-naphthol, the hydrolysis product of carbaryl by McbA. In this study, we identified McbG, a transcriptional activator of the mcbBCDEF cluster. McbG is a 315-amino-acid protein with a molecular mass of 35.7 kDa. It belongs to the LysR family of transcriptional regulators and shows 28.48% identity to the pentachlorophenol (PCP) degradation transcriptional activation protein PcpR from Sphingobium chlorophenolicum ATCC 39723. Gene disruption and complementation studies reveal that mcbG is essential for transcription of the mcbBCDEF cluster in response to 1-naphthol in strain XWY-1. The results of the electrophoretic mobility shift assay (EMSA) and DNase I footprinting show that McbG binds to the 25-bp motif in the mcbBCDEF promoter area. The palindromic sequence TATCGATA within the motif is essential for McbG binding. The binding site is located between the -10 box and the transcription start site. In addition, McbG can repress its own transcription. The EMSA results show that a 25-bp motif in the mcbG promoter area plays an important role in McbG binding to the promoter of mcbG This study reveals the regulatory mechanism for the upstream pathway of carbaryl degradation in strain XWY-1. The identification of McbG increases the variety of regulatory models within the LysR family of transcriptional regulators.IMPORTANCEPseudomonas sp. strain XWY-1 is a carbaryl-degrading strain that utilizes carbaryl as the sole carbon and energy source for growth. The functional genes involved in the degradation of carbaryl have already been reported. However, the regulatory mechanism has not been investigated yet. Previous studies demonstrated that the mcbA gene, responsible for hydrolysis of carbaryl to 1-naphthol, is constitutively expressed in strain XWY-1. In this study, we identified a LysR-type transcriptional regulator, McbG, which activates the mcbBCDEF gene cluster responsible for the degradation of 1-naphthol to salicylate and represses its own transcription. The DNA binding site of McbG in the mcbBCDEF promoter area contains a palindromic sequence, which affects the binding of McbG to DNA. These findings enhance our understanding of the mechanism of microbial degradation of carbaryl.

Project description:Pseudomonas sp. strains C5pp and C7 degrade carbaryl as the sole carbon source. Carbaryl hydrolase (CH) catalyzes the hydrolysis of carbaryl to 1-naphthol and methylamine. Bioinformatic analysis of mcbA, encoding CH, in C5pp predicted it to have a transmembrane domain (Tmd) and a signal peptide (Sp). In these isolates, the activity of CH was found to be 4- to 6-fold higher in the periplasm than in the cytoplasm. The recombinant CH (rCH) showed 4-fold-higher activity in the periplasm of Escherichia coli The deletion of Tmd showed activity in the cytoplasmic fraction, while deletion of both Tmd and Sp (Tmd+Sp) resulted in expression of the inactive protein. Confocal microscopic analysis of E. coli expressing a (Tmd+Sp)-green fluorescent protein (GFP) fusion protein revealed the localization of GFP into the periplasm. Altogether, these results indicate that Tmd probably helps in anchoring of polypeptide to the inner membrane, while Sp assists folding and release of CH in the periplasm. The N-terminal sequence of the mature periplasmic CH confirms the absence of the Tmd+Sp region and confirms the signal peptidase cleavage site as Ala-Leu-Ala. CH purified from strains C5pp, C7, and rCH?(Tmd)a were found to be monomeric with molecular mass of ?68 to 76 kDa and to catalyze hydrolysis of the ester bond with an apparent Km and Vmax in the range of 98 to 111 ?M and 69 to 73 ?mol · min-1 · mg-1, respectively. The presence of low-affinity CH in the periplasm and 1-naphthol-metabolizing enzymes in the cytoplasm of Pseudomonas spp. suggests the compartmentalization of the metabolic pathway as a strategy for efficient degradation of carbaryl at higher concentrations without cellular toxicity of 1-naphthol.IMPORTANCE Proteins in the periplasmic space of bacteria play an important role in various cellular processes, such as solute transport, nutrient binding, antibiotic resistance, substrate hydrolysis, and detoxification of xenobiotics. Carbaryl is one of the most widely used carbamate pesticides. Carbaryl hydrolase (CH), the first enzyme of the degradation pathway which converts carbaryl to 1-naphthol, was found to be localized in the periplasm of Pseudomonas spp. Predicted transmembrane domain and signal peptide sequences of Pseudomonas were found to be functional in Escherichia coli and to translocate CH and GFP into the periplasm. The localization of low-affinity CH into the periplasm indicates controlled formation of toxic and recalcitrant 1-naphthol, thus minimizing its accumulation and interaction with various cellular components and thereby reducing the cellular toxicity. This study highlights the significance of compartmentalization of metabolic pathway enzymes for efficient removal of toxic compounds.

Project description:The chromosomal region of Pseudomonas sp. strain Y2 involved in the conversion of styrene to phenylacetate (upper catabolic pathway) has been cloned and sequenced. Four catabolic genes, styABCD, and two regulatory genes, stySR, were identified. This gene cluster when transferred to Escherichia coli W confers to this phenylacetate-degrading host the ability to grow on styrene as the sole carbon and energy source. Genes styABCD are homologous to those encoding the styrene upper catabolic pathway in Pseudomonas fluorescens ST. Northern blot analyses have confirmed that genes styABCD constitute a transcription unit. The transcription start site of the sty operon was mapped 33 nucleotides upstream of the styA translational start codon. The styS and styR genes, which form an independent transcriptional unit, are located upstream of the styABCD operon, and their gene products show high similarity to members of the superfamily of two-component signal transduction systems. The styS gene product is homologous to histidine kinase proteins, whereas the styR gene product exhibits similarity at its N-terminal domain with cluster 1 of receiver modules and at its C terminus with the LuxR/FixJ family 3 of DNA-binding domains. Expression of the catabolic operon decreased significantly in the absence of the stySR genes and was restored when the stySR genes were provided in trans in the presence of styrene, suggesting that the stySR system behaves as a styrene-inducible positive regulator of the styABCD operon. Finally, a gene encoding a phenylacetyl-coenzyme A ligase that catalyzes the first step in the phenylacetate catabolism (styrene lower catabolic pathway) has been identified upstream of the styS gene. This activity was found to be induced in Pseudomonas sp. strain Y2 cells grown on styrene but not present in cells grown on glycerol. These results strongly suggest that the genes responsible for the complete mineralization of styrene are clustered in the chromosome of Pseudomonas sp. strain Y2.

Dataset Information

Insights into functional and evolutionary analysis of carbaryl metabolic pathway from Pseudomonas sp. strain C5pp.

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Insights into functional and evolutionary analysis of carbaryl metabolic pathway from Pseudomonas sp. strain C5pp.

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