Rufibacter immobilis sp. nov., isolated from a high-altitude saline lake

Abstract

Two pinkish-red, Gram-stain-negative, non-motile aerobic bacterial strains (MCC P1 T and MCC P2), capable of growing at low temperatures (15 6C), were isolated from water of a saline lake located in the western Himalayas of India. The strains were capable of growth in the presence of 0-2.0 % NaCl and at pH 6.5-9.0. Phylogenetic analysis based on 16S rRNA gene sequences revealed the closest similarity of 96.3 % to the type strain of the only species of the genus Rufibacter, Rufibacter tibetensis CCTCC AB 208084 T . Strains MCC P1 T and MCC P2 shared 99.0 % 16S rRNA gene sequence similarity and 88.6 % DNA-DNA relatedness. The major cellular fatty acids were iso-C 15 : 0 , C 17 : 1 v6c, summed feature 3 (C 16 : 1 v6c/C 16 : 1 v7c) and summed feature 4 (anteiso-C 17 : 1 B/iso-C 17 : 1 I). Predominant polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The respiratory quinone was MK-7. The DNA G+C content of the strains was 52.6-52.8 mol%. Based on morphological, physiological, chemotaxonomical and molecular characteristics, strains MCC P1 T and MCC P2 represent a novel species of the genus Rufibacter, for which the name Rufibacter immobilis sp. nov. is proposed. The type strain is MCC P1 T (5MCC 2268 T 5CCTCC AB 2013351 T ).Isolates MCC P1 T and MCC P2 were obtained during microbial diversity studies of one of the least explored high-altitude (4350 m) habitats, Pangong Lake, which extends from the Indian Himalayas to Tibet in China. The isolated strains were pinkish-red and belong to the genus Rufibacter (Abaydulla et al., 2012) based on 16S rRNA gene sequence analysis. The genus Rufibacter was distinguished from other genera of the family Cytophagaceae based on molecular, phylogenetic and phenotypic characters. At the time of writing, Rufibacter tibetensis CCTCC AB 208084 T is the only species of the genus Rufibacter with a validly published name. The novelty of the two isolated strains of the genus Rufibacter was confirmed in a taxonomic study using a polyphasic approach.Since the bacterial count appeared low in the collected samples, a 200 ml water sample was directly spread on agar plates of different nutrient media and grown under varied culture conditions (15-30 u C, pH 7-9, salinity 1-3 %) to correlate the parameters of the sampling habitat. Wellisolated colonies MCC P1 T and MCC P2 from Luria agar (M575; HiMedia) were further transferred onto agar stabs.Cultures were preserved as glycerol stocks and freeze-dried cell mass. Cell morphology was observed by phase-contrast microscopy (BX53; Olympus) and transmission electron microscopy (model TECNAI G2 20; FEI). Gram staining was performed by using a Gram staining kit (K001; HiMedia). Motility was tested by the hanging drop method and observed under a phase-contrast microscope (Suzuki et al., 2001), and confirmation was achieved using the molten agar test (Cruickshank, 1965). Since strains were pigmented, whole-cell absorption spectra were recorded using a Cary 300 UV-Vis spectrophotometer (Agilent Technologies). Anaerobi...

Rufibacter hautae sp. nov., a red-pigmented bacterium from freshwater lake sediment, and proposal of Rufibacter quisquiliarum as a latter heterotypic synonym of Rufibacter ruber

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“…Members of this genus are Gram-stainnegative, rod-shaped, non-spore-forming, with menaquinone 7 (MK-7) as the major respiratory quinone and phosphatidylethanolamine as the predominant polar lipid. Currently, the genus Rufibacter comprises seven species with validly published names: R. tibetensis from soil [1], R. roseus from radiation-polluted soil [4], R. immobilis from saline lake [5], R. ruber from fragmentary rock [6], R. glacialis from glacier soil [7], R. quisquiliarum from bioreactor treating landfill leachate [8] and R. sediminis from lake sediment [9]. The strains R. ruber and R. quisquiliarum were published in 2016 and the ANI and dDDH values between them were 98.0 and 83.0 %, respectively, which was all above the accepted cut-off [10].…”

Exploration of a Hot Spring for Thermostable Protease Producers

“…Sugar utilization pattern of selected isolates was determined by using dextrose, fructose, lactose, sucrose, mannitol, maltose, xylose, arabinose, galactose, glycerol, cellobiose, sorbitol, mellibiose, mannose, trehalose, ribose, salicin, rhamnose, inulin, adonitol, and raffinose (Sneath et al, 1986). Catalase and oxidase tests were performed by using 3 % hydrogen peroxide and 1 % tetramethyl-p-phenylenediamine dihydrochloride respectively (Polkade et al, 2015). Amylase, cellulase, gelatinase, pectinase and lipase production ability of selected isolates was evaluated by using starch, cellulose, gelatine, pectin and tributyrin substrates respectively.…”

“…cell shape, cell size, sporulation and motility of selected isolates were observed . Optimization of physical parameters for maximum growth of selected isolates was thoroughly assessed (Polkade et al, 2015). Sugar utilization pattern of selected isolates was determined by using dextrose, fructose, lactose, sucrose, mannitol, maltose, xylose, arabinose, galactose, glycerol, cellobiose, sorbitol, mellibiose, mannose, trehalose, ribose, salicin, rhamnose, inulin, adonitol, and raffinose (Sneath et al, 1986).…”

Rufibacter glacialis sp. nov., a psychrotolerant bacterium isolated from glacier soil

“…Menaquinone-7 (MK-7) is the major respiratory menaquinone and phosphatidylethanolamine is the predominant polar lipid of the genus Rufibacter. The genus comprises, at the time of writing, three recognized species (Abaydulla et al, 2012;Polkade et al, 2015; Zhang et al, 2015). During a study of bacterial diversity on glaciers in China, a strain producing red colonies (MDT1-10-3 T ) was isolated from soil collected from Midui glacier, Tibet, China.…”