Taxonomy and physiology of Pseudoxanthomonas arseniciresistens sp. nov. an arsenate and nitrate-reducing novel gammaproteobacterium from arsenic contaminated groundwater India

摘要

Reductive transformation of toxic arsenic (As) species by As reducing bacteria (AsRB) is a key process in As-biogeochemical-cycling within the subsurface aquifer environment. In this study, we have characterized a Gram-stain-negative, non-spore-forming, rod-shaped As reducing bacterium designated KAs 5-3^T, isolated from highly As-contaminated groundwater of India. Strain KAs 5-3^T displayed high 16S rRNA gene sequence similarity to the members of the genus Pseudoxanthomonas, with P. mexicana AMX 26B^T (99.25% similarity), P. japonensis 12-3^T (98.9 0%), P. putridarboris WD-12^T (98.02%), and P. indica P15^T (97.27%) as closest phylogenetic neighbours. DNA-DNA hybridization study unambiguously indicated that strain KAs 5-3^T represented a novel species that was separate from reference strains of P. mexicana AMX 26B^T (35.7%), P. japonensis 12-3^T (35.5%), P. suwonensis 4M1^T (35.5%), P. wuyuanensis XC21-2^T (35.0%), P. indica P15^T (32.5%), P. daejeonensis TR6-08^T (32.0%), and P. putridarboris WD12^T (22.1%). The DNA G+C content of strain KAs 5-3^T was 64.9 mol %. The predominant fatty acids were C15:0 (37.4%), C16:0 iso (12.6%), C17:1 iso ω9c (10.5%), C15:0 anteiso (9.5%), C11:0 iso 3-OH (8.5%), and C16:1 ω7c/ C16:1 ω6c (7.5%). The major polar lipids were diphosphatidylglycerol, phosphatidyldimethylethanolamine, phosphatidylcholine, and two unknown phospholipids (PL1, PL2). Ubiquinone 8 (Q8) was the predominant respiratory quinone and spermidine was the major polyamine of the strain KAs 5-3^T. Cells of strain KAs 5-3^T showed the ability to use O2, As⁵⁺, NO3^-, NO2^-, and Fe³⁺ as terminal electron acceptors as well as to reduce As⁵⁺ through the cytosolic process under aerobic incubations. Genes encoding arsenate reductase (arsC) for As-detoxification, nitrate- and nitrite reductase (narG and nirS) for denitrification were detected in the strain KAs 5-3^T. Based on taxonomic and physiological data, strain KAs 5-3^T is described as a new representative member of the genus Pseudoxanthomonas, for which the name Pseudoxanthomonas arseniciresistens sp. nov. is proposed. The type strain is KAs 5-3^T (= LMG 29169^T = MTCC 12116^T = MCC 3121^T).