Discovery of a Novel Gene Conferring Tellurite Tolerance Through Tellurite Reduction to Escherichia coli Transformant in
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ORIGINAL ARTICLE
Discovery of a Novel Gene Conferring Tellurite Tolerance Through Tellurite Reduction to Escherichia coli Transformant in Marine Sediment Metagenomic Library Madison Pascual Munar 1 & Hirokazu Takahashi 2 & Yoshiko Okamura 1,2 Received: 28 July 2019 / Accepted: 2 September 2019 # Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract Metagenomic library construction using a marine sediment-enrichment was employed in order to recover tellurium from tellurite, a tellurium oxyanion, dissolved in water and then functional screening was performed to discover a novel gene related to tellurite reduction. Transmission electron microscopy (TEM) revealed the formation of intracellular Te crystals in Escherichia coli cells transformed with a specific DNA fragment from the marine sediment metagenome. The metagenome fragment was composed of 691 bp and showed low homology to known proteins. Phylogenetic analysis suggested that the metagenome fragment was related to Pseudomonas stutzeri. Cloning and expression of an open reading frame (ORF) on the metagenome fragment validated the role of the fragment in conferring tellurite resistance and tellurite-reducing activity to E. coli host cells. E. coli transformant containing the ORF1 showed resistance to 1 mM Na2TeO3. The optimal tellurite-reducing activity of cells containing the ORF1 was recorded at 37 °C and pH 7.0. Keywords Metagenome library . Marine sediment . Metalloid tellurium . Tellurite reduction
Introduction Microorganisms have evolved specific mechanisms to ameliorate the deleterious effects of metals in the environment (Narayanan and Sakthivel 2010; Iravani 2014), offering great potential for use in the bioremediation of toxic metal wastes. Thus, microorganisms might provide an alternative technology for metal recovery (Klaus-Joerger et al. 2001; Narayanan and Sakthivel 2010). Studies of bacterial tellurite resistance and reduction mechanisms mainly focus on the elucidation of genes
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10126-019-09922-w) contains supplementary material, which is available to authorized users. * Yoshiko Okamura
1
Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Hiroshima, Japan
2
Unit of Biotechnology, Graduate School of Integrated Sciences for Life, Hiroshima University, Hiroshima, Japan
and proteins involved in metal exclusion or detoxification. As a result, housekeeping genes, cell membrane-bound flavoproteins, and cytosolic oxidoreductases involved in tellurite resistance, susceptibility, transport, binding, accumulation, efflux/influx, and reduction have been characterized (Jobling and Ritchie 1987; Jobling and Ritchie 1988; Moore and Kaplan 1992; Hill et al. 1993; Whelan et al. 1995; Avazeri et al. 1997; Taylor 1999; Turner et al. 2001; Taylor et al. 2002; Calderón et al. 2006; Pérez et al. 2007; Castro et al. 2008; Chasteen et al. 2009). In addition, tellurite-resistant bacterial strain
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