Search

Genome of Alcanivorax sp. IO_7, an alkane degrading deep-sea bacteria isolated from hydrothermally-influenced Southwest Indian Ridge was sequenced and analysed. Genomic data mining revealed gene clusters for degrading n-alkane and cycloalkanes, including biosurfactant production. The strain was shown to grow on hexadecane as its sole carbon source, supporting the findings of genomic analysis. Presence of cyclohexanone monooxygenase among genomic islands suggest that this strain may have used gene transfer to enhance its hydrocarbon degradation ability. Genes encoding for heavy metal resistance, multidrug resistance and multiple natural product biosynthesis crucial for survival in the hydrothermally influenced deep sea environment were detected. In our comparative genome analysis, it was evident that marine Alcanivorax strains contain a suite of enzymes for n-alkane and haloalkanoate degradation. Comparative genome and genomic synteny analysis provided insights into the physiological features and adaptation strategies of Alcanivorax sp. IO_7 in the deep-sea hydrothermal environment.

A Gram-negative, aerobic, non-motile, oxidase-positive, catalase-positive, rod-shaped bacterium, designated strain MCCB 386T was isolated from sediment samples collected from Kongsfjorden, an Arctic fjord. The strain MCCB 386T showed growth at 4–37 °C (optimum 27°C) in the presence of 1–8% NaCl (w/v, optimum 3.5%) and at pH 6.0–8.0 (optimum pH 7.0). The major fatty acids were C18:1ω7c (54.0%) and 11-methyl C18:1ω7c (22.6%). The dominant respiratory quinone was Q-10. The major polar lipids comprised of phosphatidylcholine (PC), diphosphatidylglycerol (DPG), phosphatidylglycerol (PG), phosphoglycolipid (PGL), one unidentified aminolipid, two glycolipids and two unidentified lipids. The genomic G+C content of the strain MCCB 386T was 68.1 mol%. The 16 S rRNA gene sequences based phylogenetic analysis of MCCB 386T showed that Psychromarinibacter halotolerans YBW34T (95.88%) is the most closely related species. In addition, overall genome relatedness indices (OGRI) of MCCB 386T with closely related strains were lower than threshold level for species and genus delineation. The analysis of Biosynthetic Gene clusters (BGCs) revealed the potential of this strain for production of novel bioactive secondary metabolites. As per polyphasic taxonomic characterisation, strain MCCB 386T represents a novel species of a novel genus for which the name Roseitranquillus sediminis gen. nov., sp. nov. is suggested. The type strain of the species is MCCB 386T (= JCM 33,538T= KACC 21,531T).

The bacterial reduction of mercury is one of the transformation processes where ionic form (Hg2+) converts into elemental form (Hg0). The biological reduction of mercury is facilitated by the mercuric reductase (merA) gene. The significance of understanding the role of microbial mercury reduction in the Arctic during the changing climate conditions is high as it acts as the sink as well as a source of mercury. The present study was carried out to assess the prevalence of mercury tolerant bacteria and to know the distribution of merA in the Arctic bacterial communities. Citrobacter freundii strain MM7, a psychrotrophic, gram-negative, facultative anaerobic, non-traditional sulphate-reducing bacterium, isolated from the sediments of Kongsfjorden showed tolerance to mercury up to 10.0 mg/L in vitro. Mercury removal experiment confirmed the removal of ∼80% of mercury mediated by plasmid-borne merA gene. Studies using Fourier transform infrared (FTIR) showed the metabolic changes incited by mercury, and the spectroscopic differences reflected that the functional groups like alkynes, aromatic phosphates, organic phosphates, methyl, methylene, and amide groups present in the bacterial surface owe a significant part in Hg biosorption and removal. The present study provides insights on the mercury resistance in an Arctic bacterial strain and suggests the potential application of Citrobacter freundii strain MM7 in the bioremediation of mercury from the natural environment.

The whole genome of Alteromonas pelagimontana 5.12T, a psychrotolerant deep-sea bacterium isolated from the sediment sample of eastern Southwest Indian Ridge, was sequenced and analysed for understanding its metabolic capacities and biosynthesis potential of natural products. The circular genome contained 4.3 Mb with a GC content of 42.6 mol%. Genomic data mining revealed a gene cluster for heavy metal resistance (czcABC, acrB, arsR1, copA, nikA, mntH, mntP), exopolysaccharides (EPS; epsCDEFHLM) and polyhydroxyalkanoates (PHA; phbC) production, as well as genes involved in complex polysaccharide degradation. Genes that could allow strain 5.12T to cope with acid stress (ibaG) and heat shock (ibpA, hslR) were observed along with ten chaperone-encoding genes which could possibly play vital role in adaptability of this strain to the hydrothermally influenced environment. Gene clusters for secondary metabolite production such as bacteriocin and arylpolyene were also predicted. Thus, genome sequencing and data mining provided insights into the molecular mechanisms involved in the adaptation to hydrothermally influenced deep-sea environment that could promote further experimental exploration.

A novel exopolysaccharide-producing strain, designated as 5.12T, was isolated from a sediment sample from the Southwest Indian Ridge, Indian Ocean. The strain was Gram-stain-negative, motile, strictly aerobic, and oxidase- and catalase-positive. It grew optimally at 35 °C, at pH 6.0 and in the presence of 3.5 % (w/v) NaCl. Its major isoprenoid quinone was ubiquinone-8 (Q-8) and summed feature 3 (comprising C16 : 1ω6c and/or C16 : 1ω7c), C16 : 0 and C18 : 1ω7c were the major cellular fatty acids. The DNA G+C content was 46.1 mol%. 16S rRNA gene sequence analysis suggested that strain 5.12T is a member of the genus Alteromonas . Strain 5.12T exhibited close 16S rRNA gene sequence similarity to Alteromonas lipolytica JW12T (96.1 %), Alteromonas hispanica F-32T (95.9 %), Alteromonas confluentis DSSK2-12T (95.9 %), Alteromonas litorea TF-22T (95.6 %) and Alteromonas mediterranea DET (95.5 %). Strain 5.12T contained phosphatidylethanolamine and phosphatidylglycerol as the major polar lipids. Owing to significant differences in the 16S rRNA gene sequences, as well as the phenotypic and chemotaxonomic characteristics, the novel isolate described here merits classification as a representative of a novel species of the genus Alteromonas , for which the name Alteromonas pelagimontana sp. nov. is proposed. The type strain of this species is 5.12T (LMG 29661T= MCC 3250T).

Idiomarina sp. strain 5.13, able to produce biopolymer and exopolysaccharide, was isolated from a sediment sample collected from the Southwest Indian Ridge, Indian Ocean. Analysis of its draft genome sequence provides insights into its remarkable stress tolerance and offers the genetic basis for harnessing the biotechnological potential of this strain.

We report the expression pattern of heat shock proteins (HSPs) in an Antarctic psychrotrophic strain of Cellulosimicrobium cellulans (DSM 22151) by comparing with its mesophilic counterpart (DSM 43879T) at different temperatures. In both strains, the synthesis of HSPs declined with growth phase. The Antarctic isolate could upregulate 60 kDa, 52 kDa and 41.6 kDa HSPs at 60°C while for its mesophilic counterpart, regulation was restricted to a 64 kDa fraction. The highly unstable nature of this fraction could have led to the impaired thermotolerance exhibited by the mesophilic strain. The downshift of thermal shock from 60°C to 45°C resulted in further upregulation of HSPs in the psychrotrophic strain, while there was no marked variation in the mesophilic strain. This work highlights the significance of a 60 kDa protein in the Antarctic strain of C. cellulans and also indicates the role of a 52 kDa protein in the previously reported heat shock response. Contrary to expectations, the psychrotrophic strain was found to have better mechanisms to tolerate higher temperatures—a property that could give valuable insights into the evolution and adaptation of cold-adapted bacteria.

Metal tolerant bacterial strains viz Bacillus cereus (RS-1), Bacillus sp. (RS-2) and Chromohalobacter beijerinckii (RS-3) were isolated from the surface sediments of a solar saltern in Ribandar Goa, situated in the vicinity of the Mandovi estuary influenced by mining activities. RS-1 that showed optimal growth at 20 psu salinity was tolerant to 10 mM Co2+ while hypersaline isolates RS-2 (100 psu) and RS-3 (200 psu) were tolerant to Ni2+ and Mn2+ at 1 mM and 10 mM respectively. Experimental studies revealed that growth was stimulated at low concentrations of metal amendments for all the isolates. Growth of RS-1 was stimulated by ~450% on addition of 100 µM Co2+ whereas for RS-2 and RS-3 it was at 100 µM Ni2+ (70%) and 5 mM Mn2+ (450%). The stimulation in growth was coupled to a dip in respiration rates for the isolates RS-1 and RS-3 when compared to metal unamended controls. The respiration rates for RS-1 and RS-3 during peak growth in the presence of metal were 17.0 and 27.5 compared to the controls which were 24.7 and 473.4 pg formazan cell-1 day-1 respectively. Presence of Ni2+ stimulated the respiration rate (26%) in RS-2 when compared to the control (417.4 pg formazan cell-1 day-1). Co2+ and Mn2+ had a significant negative impact on the utilization of carbohydrates and carboxylic acids in RS-1 and RS-3 respectively. Ni2+ had a stimulatory effect on the utilization of BIOLOG GP2 substrates by RS-2. The phenotypic expressions observed above were correlated with the changes in whole cell protein profiles in the presence and absence of added metal. Addition of Co2+ to RS-1 resulted in a significant up-regulation of 57 kDa fraction while there was a conspicuous down-regulation of 29 kDa protein. The major protein fraction up-regulated in RS-2 in the presence of Ni2+ was a 59 kDa protein while most of the fractions were down-regulated. In RS-3, the addition of Mn2+ at 10, 100 and 1000 µM up-regulated a 50 kDa protein while the 53 kDa fraction was down-regulated. This study relates the metal induced regulation of proteins to phenotypic variations encountered in growth and substrate utilization.

The diversity and abundance of retrievable pelagic heterotrophic bacteria in Kongsfjorden, an Arctic fjord, was studied during the summer of 2011 (June, August, and September). Retrievable bacterial load ranged from 10 3 to 10 7 CFU L −1 in June, while it was 10 4 –10 6 CFU L −1 in August and September. Based on 16S rRNA gene sequence similarities, a higher number of phylotypes was observed during August (22 phylotypes) compared to that during June (6 phylotypes) and September (12 phylotypes). The groups were classified into four phyla: Firmicutes, Actinobacteria, Proteobacteria , and Bacteroidetes. Bacteroidetes was represented only by a single member Leewenhoekiella aequorea during the three months and was dominant (40%) in June. However, this dominance changed in August to a well-known phytopathogenic species Rhodococcus fascians (32%), which could be a result of decrease in the phytoplankton biomass following the secondary bloom. It is the first report of Halomonas titanicae isolation from the Arctic waters. It showed an increase in its abundance with the intrusion of Atlantic water into Kongsfjorden. Increased abundance of Psychrobacter species in the late summer months coincided with the presence of cooler waters. Thus, the composition and function of heterotrophic bacterial community was fundamentally different in different months. This could be linked to the changes in the water masses and/or phytoplankton bloom dynamics occurring in Arctic summer.