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

<div><p>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 <i>Pseudoxanthomonas</i>, with <i>P</i>. <i>mexicana</i> AMX 26B^T (99.25% similarity), <i>P</i>. <i>japonensis</i> 12-3^T (98.9 0%), <i>P</i>. <i>putridarboris</i> WD-12^T (98.02%), and <i>P</i>. <i>indica</i> 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 <i>P</i>. <i>mexicana</i> AMX 26B^T (35.7%), <i>P</i>. <i>japonensis</i> 12-3^T (35.5%), <i>P</i>. <i>suwonensis</i> 4M1^T (35.5%), <i>P</i>. <i>wuyuanensis</i> XC21-2^T (35.0%), <i>P</i>. <i>indica</i> P15^T (32.5%), <i>P</i>. <i>daejeonensis</i> TR6-08^T (32.0%), and <i>P</i>. <i>putridarboris</i> WD12^T (22.1%). The DNA G+C content of strain KAs 5-3^T was 64.9 mol %. The predominant fatty acids were C_15:0 (37.4%), C_16:0 iso (12.6%), C_17:1 iso ω9c (10.5%), C_15:0 anteiso (9.5%), C_11:0 iso 3-OH (8.5%), and C_16:1 ω7c/ C_16:1 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 (<i>ars</i>C) for As-detoxification, nitrate- and nitrite reductase (<i>nar</i>G and <i>nir</i>S) 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 <i>Pseudoxanthomonas</i>, for which the name <i>Pseudoxanthomonas arseniciresistens</i> sp. nov. is proposed. The type strain is KAs 5-3^T (= LMG 29169^T = MTCC 12116^T = MCC 3121^T).</p>