Metagenomic cloning and characterization of Na + transporters from Huamachi Salt Lake in China

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Abstract

Moderately halophilic bacteria are a kind of extreme environment microorganism that can tolerate moderate salt concentrations ranging from 0.5M to 2.5M. Here, via a metagenomic library screen, we identified four putative Na + transporters, designated H7-Nha, H16-Mppe, H19-Cap and H35-Mrp, from moderately halophilic community in the hypersaline soil of Huamachi Salt Lake, China. Functional complementation observed in a Na + (Ca 2+ )/H + antiporter-defective Escherichia coli mutant (KNabc) suggests that the four putative Na + transporters could confer cells a capacity of Na + resistance probably by enhancing Na + or Ca 2+ efflux, but not Li + or K + exchange. Blastp analysis of the deduced amino-acid sequences indicates that H7-Nha has 71% identity to the NhaG Na + /H + antiporter of Bacillus subtilis, while H19-Cap shows 99% identity to Enterobacter cloacae Ca 2+ antiporter. Interestingly, H16-Mppe shares 59% identity to the metallophosphoesterase of Bacillus cellulosilyticus and H35-Mrp shows 68% identity to multidrug resistance protein of Lysinibacillus sphaericus. This is the first report that predicts a potential role of metallophosphoesterase in Na + resistance in halophilic bacteria. Furthermore, everted membrane vesicles prepared from E. coli cells harboring H7-Nha exhibit Na + /H + antiporter activity, but not Li + (K + )/H + antiporter activity, confirming that H7-Nha supports Na + resistance mainly via Na + /H + antiport. Our report also demonstrates that metagenomic library screen is a convenient and effective way to explore more novel types of Na + transporters. © 2012 Elsevier GmbH.

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Gao, M., Tao, L., & Chen, S. (2013). Metagenomic cloning and characterization of Na + transporters from Huamachi Salt Lake in China. Microbiological Research, 168(2), 119–124. https://doi.org/10.1016/j.micres.2012.06.004

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