Identification of genes conferring arsenic resistance to Escherichia coli from an effluent treatment plant sludge metagenomic library

Abstract

The majority of bacteria elude culture in the laboratory. A metagenomic approach provides culture-independent access to the gene pool of the whole bacterial community. A metagenomic library was constructed from an industrial effluent treatment plant sludge containing about 1.25 Gb of microbial community DNA. Two arsenic-resistant clones were selected from the metagenomic library. Clones MT3 and MT6 had eight- and 18-fold higher resistance to sodium arsenate in comparison with the parent strain, respectively. The clones also showed increased resistance to arsenite but not to antimony. Sequence analysis of the clones revealed genes encoding for putative arsenate reductases and arsenite efflux pumps. A novel arsenate resistance gene (arsN) encoding a protein with similarity to acetyltransferases was identified from clone MT6. ArsN homologues were found to be closely associated with arsenic resistance genes in many bacterial genomes. ArsN homologues were found fused to putative arsenate reductases in Methylibium petroleiphilum PM1 and Anaeromyxobacter dehalogenans 2CP-C and with a putative arsenite chaperone in Burkholderia vietnamiensis G4. ArsN alone resulted in an approximately sixfold higher resistance to sodium arsenate in wild-type Escherichia coli W3110.

Molecular identification of arsenic-resistant estuarine bacteria and characterization of their ars genotype

“…Thus, this study helps to correlate the occurrence of the ars genotype with the level of arsenic pollution in these waters. The arsenical resistance in isolates with genotypes arsA (SPK14, SP45 and SP9), arsAC (VKM05, SK4, SK1, SK2 and SK3), arsBC (SP02) and arsAB (SPK05) may also be conferred by other factors like GSH or other isoforms of ars genes (Ordonez et al 2005) and other ars genes like arsN, arsM, arsO and arsT (Qin et al 2006;Wang et al 2006;Chauhan et al 2009). The PCR negative result in rest of the arsenicresistant isolates may be either due to sequence differences between ars genes and primers used in this study or because of the diversity of arsenic resistance genes (Jackson and Dugas 2003;Achour et al 2007).…”

Integrated Perspective for Effective Bioremediation

“…One such example is provided by arsenic-resistant genes from effluent treatment plant (ETP) sludge. Two clones were selected, and a novel arsenicresistant gene was identified [28].…”

Carl Woese: from Biophysics to Evolutionary Microbiology

“…In past 10-15 years Indian research in microbial cultivation and taxonomy has made good progress and till date we have described more than 300 novel taxa in International Journal of Systematic and Evolutionary Microbiology from different niches (http://www.bacterio.cict.fr) [8,9,29,30,37]. In the past few years there have been studies on microbial diversity of diverse habitats including the Western Ghats [45], psychrophilic habitat of Pangong Lake, Antarctic and Arctic soil and sediments [6,7,42], effluent treatment plant and pesticide contaminated dumpsite [3,35,39,41] marine sediment [43] and human gut [9,20,25]. Some laboratories have also focused their attention on SSU rRNA gene sequences and developed a phylogenetic framework, detected species specific signature sequences and designed improved PCR-primers using bioinformatic tools to improve the taxonomic resolution and environmental detection of related microorganisms [13,16,28,33].…”