Enterobacter nickelidurans sp. nov., a novel nickel tolerant enterobacteria isolated from Torsa river water of India

Abstract

A Gram-negative, rod-shaped, nickel-resistant bacterium, designated as strain NiVas 114', was isolated from waters of Torsa River in Hasimara, West Bengal, India. The strain NiVasl 14 possessing inducible nickel resistance can tolerate maximally 10mM nickel chloride. Southern blot assays of genomic DNA of NiVas 114 using probe(s) generated from known nickel resistance determinants (cnr/ ncc/ nrel nerí nir). under conditions of low stringency, produced no detectable signal except for cnrA gene of Ralstonia metallidurans CH34 (formerly Alcaligenes eutropha CH34) in which weak hybridization signal occurred. Based on 16S rRNA gene sequence similarity, strain NiVas 114 was identified as a member of y Proteobacteria, and the nearest phylogenetic relatives are Enterobacter hormaechei (98.6-98.5%) and Enterobacter cloacae (97.5-98.2 %). In the phylogenetic trees constructed with nucleotide sequence of 16S rRNA gene, hsp60 gene and rpoB gene, strain NiVas 114" clustered with the subspecies of Enterobacter hormaechei. The strain showed DNA-DNA relatedness of 60 -63% with Enterobacter hormaechei subsp hormaechei, Enterobacter hormaechei subsp. oharae, Enterobacter hormaechei subsp. steigerwalti Enterobacter cloacae subsp. cloacae and Enterobacter cloacae subsp. dissobvens. The isolate NiVas 114 differed from the nearest phylogenetic relatives in terms of number of phenotypic characteristics. The G+C content of the genomic DNA of the isolate was 59.5 +0.4 mol %. The predominant cellular faty acids of the isolate are C160, Summed feature 3 (comprises C16wTel 15 io 201) and C 18 w7ei hydroxy fatty acids are found in minor quantities. Thus, on the basis of biochemical characteristics, fatty acid profiles, DNA-DNA relatedness and phylogenetic analysis, the isolate was recognized as a novel species of Enterobacter. for which the name Enterobacter nickellidurans sp. nov. is proposed with the type strain NiVas 114' (= LMG 23000 = CcUGSO594"= JCM13045").