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Sequencing and expression of two arsenic resistance operons with different functions in the highly arsenic-resistant strain Ochrobactrum tritici SCII24T.

ABSTRACT: BACKGROUND: Arsenic (As) is a natural metalloid, widely used in anthropogenic activities, that can exist in different oxidation states. Throughout the world, there are several environments contaminated with high amounts of arsenic where many organisms can survive. The most stable arsenical species are arsenate and arsenite that can be subject to chemically and microbiologically oxidation, reduction and methylation reactions. Organisms surviving in arsenic contaminated environments can have a diversity of mechanisms to resist to the harmful effects of arsenical compounds. RESULTS: The highly metal resistant Ochrobactrum tritici SCII24 was able to grow in media with arsenite (50 mM), arsenate (up to 200 mM) and antimonite (10 mM). This strain contains two arsenic and antimony resistance operons (ars1 and ars2), which were cloned and sequenced. Sequence analysis indicated that ars1 operon contains five genes encoding the following proteins: ArsR, ArsD, ArsA, CBS-domain-containing protein and ArsB. The ars2 operon is composed of six genes that encode two other ArsR, two ArsC (belonging to different families of arsenate reductases), one ACR3 and one ArsH-like protein. The involvement of ars operons in arsenic resistance was confirmed by cloning both of them in an Escherichia coli ars-mutant. The ars1 operon conferred resistance to arsenite and antimonite on E. coli cells, whereas the ars2 operon was also responsible for resistance to arsenite and arsenate. Although arsH was not required for arsenate resistance, this gene seems to be important to confer high levels of arsenite resistance. None of ars1 genes were detected in the other type strains of genus Ochrobactrum, but sequences homologous with ars2 operon were identified in some strains. CONCLUSION: A new strategy for bacterial arsenic resistance is described in this work. Two operons involved in arsenic resistance, one giving resistance to arsenite and antimonite and the other giving resistance to arsenate were found in the same bacterial strain.

SUBMITTER: Branco R

PROVIDER: S-EPMC2440759 | biostudies-literature | 2008

REPOSITORIES: biostudies-literature

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Sequencing and expression of two arsenic resistance operons with different functions in the highly arsenic-resistant strain Ochrobactrum tritici SCII24T.

Branco Rita R Chung Ana-Paula AP Morais Paula V PV

BMC microbiology 20080613

<h4>Background</h4>Arsenic (As) is a natural metalloid, widely used in anthropogenic activities, that can exist in different oxidation states. Throughout the world, there are several environments contaminated with high amounts of arsenic where many organisms can survive. The most stable arsenical species are arsenate and arsenite that can be subject to chemically and microbiologically oxidation, reduction and methylation reactions. Organisms surviving in arsenic contaminated environments can hav ...[more]

PMID: 18554386

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Project description:Substantial concentrations of penicillin V potassium (PVK) have been found in livestock manure, soil, and wastewater effluents, which may pose potential threats to human health and contribute to the emergence of penicillin-resistant bacterial strains. In this study, bacterial strains capable of degrading PVK were isolated from sludge and characterized. Strain X-2 was selected for biodegradation of PVK. Based on morphological observations and 16S rRNA gene sequencing, strain X-2 was identified as an Ochrobactrum tritici strain. To enhance the PVK degradation ability of PVK, a whole-cell biodegradation process of Ochrobactrum tritici X-2 was established and optimized. In the whole-cell biodegradation process, the optimal temperature and pH were 30°C and 7.0, respectively. Under the optimized conditions, the degradation rate using 0.5?mg/ml PVK reached 100% within 3 h. During biodegradation, two major metabolites were detected: penicilloic acid and phenolic acid. The present study provides a novel method for the biodegradation of PVK using Ochrobactrum tritici strains, which represent promising candidates for the industrial biodegradation of PVK.IMPORTANCE Substantial concentrations of penicillin V potassium (PVK) have been found in the environment, which may pose potential threats to human health and contribute to the emergence of penicillin-resistant bacterial strains. In this study, antibiotic-degrading bacterial strains for PVK were isolated from sludge and characterized. Ochrobactrum tritici was selected for the biodegradation of PVK with high efficiency. To enhance its PVK degradation ability, a whole-cell biodegradation process was established and optimized using Ochrobactrum tritici The degradation rate with 0.5?mg/ml PVK reached 100% within 3 h. The potential biodegradation pathway was also investigated. To the best of our knowledge, the present study provides new insights into the biodegradation of PVK using an Ochrobactrum tritici strain, a promising candidate strain for the industrial biodegradation of ?-lactam antibiotics.

Dataset Information

Sequencing and expression of two arsenic resistance operons with different functions in the highly arsenic-resistant strain Ochrobactrum tritici SCII24T.

Publications

Sequencing and expression of two arsenic resistance operons with different functions in the highly arsenic-resistant strain Ochrobactrum tritici SCII24T.

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