Degradation Pathways of 2- and 4-Nitrobenzoates in Cupriavidus sp. Strain ST-14 and Construction of a Recombinant Strain, ST-14::3NBA, Capable of Degrading 3-Nitrobenzoate.
Appl Environ Microbiol
; 82(14): 4253-4263, 2016 07 15.
Article
em En
| MEDLINE
| ID: mdl-27208126
ABSTRACT
UNLABELLED Strain ST-14, characterized as a member of the genus Cupriavidus, was capable of utilizing 2- and 4-nitrobenzoates individually as sole sources of carbon and energy. Biochemical studies revealed the assimilation of 2- and 4-nitrobenzoates via 3-hydroxyanthranilate and protocatechuate, respectively. Screening of a genomic fosmid library of strain ST-14 constructed in Escherichia coli identified two gene clusters, onb and pob-pca, to be responsible for the complete degradation of 2-nitrobenzoate and protocatechuate, respectively. Additionally, a gene segment (pnb) harboring the genes for the conversion of 4-nitrobenzoate to protocatechuate was unveiled by transposome mutagenesis. Reverse transcription-PCR analysis showed the polycistronic nature of the gene clusters, and their importance in the degradation of 2- and 4-nitrobenzoates was ascertained by gene knockout analysis. Cloning and expression of the relevant pathway genes revealed the transformation of 2-nitrobenzoate to 3-hydroxyanthranilate and of 4-nitrobenzoate to protocatechuate. Finally, incorporation of functional 3-nitrobenzoate dioxygenase into strain ST-14 allowed the recombinant strain to utilize 3-nitrobenzoate via the existing protocatechuate metabolic pathway, thereby allowing the degradation of all three isomers of mononitrobenzoate by a single bacterial strain. IMPORTANCE Mononitrobenzoates are toxic chemicals largely used for the production of various value-added products and enter the ecosystem through industrial wastes. Bacteria capable of degrading mononitrobenzoates are relatively limited. Unlike other contaminants, these man-made chemicals have entered the environment since the last century, and it is believed that bacteria in nature evolved not quite efficiently to assimilate these compounds; as a consequence, to date, there are only a few reports on the bacterial degradation of one or more isomers of mononitrobenzoate. In the present study, fortunately, we have been able to isolate a Cupriavidus sp. strain capable of assimilating both 2- and 4-nitrobenzoates as the sole carbon source. Results of the biochemical and molecular characterization of catabolic genes responsible for the degradation of mononitrobenzoates led us to manipulate a single enzymatic step, allowing the recombinant host organism to expand its catabolic potential to assimilate 3-nitrobenzoate.
Texto completo:
1
Coleções:
01-internacional
Contexto em Saúde:
3_ND
Base de dados:
MEDLINE
Assunto principal:
Escherichia coli
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Cupriavidus
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Redes e Vias Metabólicas
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Engenharia Metabólica
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Nitrobenzoatos
Idioma:
En
Revista:
Appl Environ Microbiol
Ano de publicação:
2016
Tipo de documento:
Article