RESUMO
Arsenic (As) is a widely distributed toxic element in the environment and microorganisms have developed resistance mechanisms in order to tolerate it. The cellular response of the chemoorganotrophic arsenite (As[III])-oxidizing α-Proteobacteria, Sinorhizobium sp. strain A2, to arsenic was examined in the present study. Several proteins associated with arsenite oxidase and As resistance were shown to be accumulated in the presence of As(III). A shift in central carbon metabolism from the tricarboxylic acid pathway to glyoxylate pathway was also observed in response to oxidative stress. Our results revealed the strategy of the As(III)-oxidizing Sinorhizobium strain to mitigate arsenic toxicity and oxidative damage by multiple metabolic adaptations.
Assuntos
Arsenitos/toxicidade , Farmacorresistência Bacteriana , Sinorhizobium/efeitos dos fármacos , Estresse Fisiológico , Carbono/metabolismo , Análise do Fluxo Metabólico , Redes e Vias Metabólicas , Oxirredução , Oxirredutases/metabolismoRESUMO
Antimony (Sb) is a naturally occurring toxic element commonly associated with arsenic (As) in the environment and both elements have similar chemistry and toxicity. Increasing numbers of studies have focused on microbial As transformations, while microbial Sb interactions are still not well understood. To gain insight into microbial roles in the geochemical cycling of Sb and As, soils from Sb mine tailing were examined for the presence of Sb- and As-oxidizing bacteria. After aerobic enrichment culturing with As(III) (10 mM) or Sb(III) (100 µM), pure cultures of Pseudomonas- and Stenotrophomonas-related isolates with Sb(III) oxidation activities and a Sinorhizobium-related isolate capable of As(III) oxidation were obtained. The As(III)-oxidizing Sinorhizobium isolate possessed the aerobic arsenite oxidase gene (aioA), the expression of which was induced in the presence of As(III) or Sb(III). However, no Sb(III) oxidation activity was detected from the Sinorhizobium-related isolate, suggesting the involvement of different mechanisms for Sb and As oxidation. These results demonstrate that indigenous microorganisms associated with Sb mine soils are capable of Sb and As oxidation, and potentially contribute to the speciation and mobility of Sb and As in situ.
Assuntos
Antimônio/metabolismo , Arsênio/metabolismo , Pseudomonas/isolamento & purificação , Sinorhizobium/isolamento & purificação , Microbiologia do Solo , Stenotrophomonas/isolamento & purificação , Aerobiose , Análise por Conglomerados , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Dados de Sequência Molecular , Oxirredução , Filogenia , Pseudomonas/classificação , Pseudomonas/genética , Pseudomonas/metabolismo , RNA Ribossômico 16S/genética , Análise de Sequência de DNA , Sinorhizobium/classificação , Sinorhizobium/genética , Sinorhizobium/metabolismo , Stenotrophomonas/classificação , Stenotrophomonas/genética , Stenotrophomonas/metabolismoRESUMO
A tributyltin (TBT) resistance gene was isolated from the TBT-resistant marine origin bacterium Pseudomonas aeruginosa 25W. This gene was identical to PA0320 deposited in the P. aeruginosa PAO1 database (http://www.pseudomonas.com). The deduced amino acid sequence of PA0320 appears to be homologous to the YgiW proteins of Escherichia coli and Salmonella enterica. The deletion mutant of PA0320 showed a reduction of growth rate in the presence of TBT. A susceptibility test to cadmium, mercury, hydrogen peroxide and acidic pH in the deletion mutant showed an increasing susceptibility to them. PA0320 plays a certain role in stress tolerance against TBT as well as in stressors producing reactive oxygen species.