Chryseobacterium cupriresistens sp. nov., a copper-resistant bacterium isolated from soil contaminated with heavy metals in Chapala Basin, Mexico.

Abstract

A polyphasic taxonomic study was carried out on the bacterial EZn1^T, isolated from heavy-metal-contaminated soil in the Chapala Basin, Mexico. This Gram-negative, aerobic, rod-shaped bacterium formed orange-pigmented colonies, producing the pigment flexirubin. Analysis of the 16S rRNA gene sequence revealed that EZn1^T represents a member of the genus Chryseobacterium in the family Weeksellaceae and is closely related to Chryseobacterium cucumeris GSE06^T (98.3%), Chryseobacterium phosphatilyticum ISE14^T (97.7%) and Chryseobacterium indologenes NBCR 14944^T (97.5%). The average nucleotide identity between the genomes of strain EZn1^T and C. cucumeris GSE06^T was 90.9%, and digital DNA-DNA hybridization showed values of less than 70% with the type strains for the related species. The polar lipids present in the strain included phosphatidylethanolamine, phosphatidylglycerol, glycolipids and unidentified aminoglycolipids, whereas the major cellular fatty acids included iso-C_15 : 0 and iso-C_17 : 0 3-OH. The whole genome of EZn1^T was 5,003,090 bp in length, with a DNA G+C content of 36.7 mol %. The strain EZn1^T showed physiological characteristics different from those of closely related Chryseobacterium species. This strain showed resistance to copper (20 mM), and its genome contained genes that may confer resistance to this metal and other heavy metals (As, Cd, Co, Cr, Hg, K, Mg, Mo, Na and Zn). According to the polyphasic analysis, the strain EZn1^T (=TSD-322^T=CAIM 1954^T) is a novel species that we named Chryseobacterium cupriresistens sp. nov.