Search

We isolated four Thermus thermophilus strains from Arima Hot Spring in Japan. Complete genome sequencing revealed that they showed average nucleotide identities of ≥99.21% to each other and to strains previously isolated from the same spot, but of ≤97.86% to strains from geographically different spots in Japan, reflecting habitat-specific genomic conservation.

Citrobacter braakii AN-PRR1 is a potential salt-tolerant, plant growth-promoting rice rhizobacterium isolated from Pakistani soil. The 4.9-Mb draft genome sequence contributes to its taxonomic classification and will reveal the genes putatively responsible for its osmoprotectant and plant growth-promoting activity.

Halomonas sp. strain KAO is an aerobic, Mn(II)-oxidizing, halophilic bacterium. The draft genome of the isolate contains 47 contigs encompassing 3.7 Mb and a G+C content of 64.22%. This sequence will provide essential information for future studies of Mn(II) oxidation, particularly under halophilic conditions.

Dimethylsulfoniopropionate (DMSP) is a key component of the global geochemical sulfur cycle that is a secondary metabolite produced in large quantities by marine phytoplankton and utilized as an osmoprotectant. Bacterial DMSP lyases convert DMSP to the climate active gas dimethylsulfide (DMS). Whether marine bacteria can also accumulate DMSP as an osmoprotectant to maintain the turgor pressure of the cell in response to changes in external osmolarity remains unknown. The marine halophile Vibrio parahaemolyticus, contains at least six osmolyte transporters, four betaine carnitine choline transport (BCCT) carriers BccT1-BccT4 and two ABC-family ProU transporters. In this study, we showed that DMSP is used as an osmoprotectant by V. parahaemolyticus and several other Vibrio species including V. cholerae and V. vulnificus. Using a V. parahaemolyticus proU double mutant, we demonstrated that these ABC transporters are not required for DMSP uptake. However, a bccT null mutant lacking all four BCCTs had a growth defect compared to wild type in high salt media supplemented with DMSP. Using bccT triple mutants, possessing only one functional BCCT, in growth pattern assays, we identified two BCCT-family transporters, BccT1 and BccT2 are carriers of DMSP. Vibrio cholerae and V. vulnificus, only contain a homolog of BccT3 and functional complementation in Escherichia coli MKH13 showed only V. cholerae BccT3 could transport DMSP. In V. vulnificus strains, we identified and characterized an additional BCCT transporter that was also a carrier for DMSP. Phylogenetic analysis uncovered at least 11 distinct BCCT transporters among members of the Harveyi clade, with some species having up to 9 BCCTs as exemplified by V. jasicida.ImportanceDMSP is present in the marine environment, produced in large quantities by marine phytoplankton as an osmoprotectant, and is an important component of the global geosulfur cycle. The bacterial family Vibrionaceae is comprised of marine species, many of which are halophiles such as V. parahaemolyticus, which can utilize a wide range of osmolytes and possesses at least six transporters for the uptake of these compounds. Here, we demonstrated that V. parahaemolyticus and other Vibrio species can accumulate DMSP as an osmoprotectant and show that the BCCT family transporters were required. DMSP was transported by four different BCCT transporters; BccT1, BccT2, BccT3 and BccT5 depending on the species. Bioinformatics and phylogenetics demonstrated that Vibrio species contain a large number of BCCTs and that many of these are associated with different metabolic pathways.

The draft genome sequence of a moderately halophilic bacterium, Halomonas titanicae strain TAT1, isolated from production water of the Romashkinskoe oilfield (Russia) is presented. The genome is annotated for elucidation of the metabolic pathways involved in hydrocarbon degradation and nitrate reduction in petroleum-contaminated hypersaline environments.

The halophilic bacterium Salinivibrio sp. strain EAGSL was isolated from the Great Salt Lake (Utah) for use in microbial electrochemical technologies experiencing fluctuating salt concentrations. Genome sequencing was performed with Ion Torrent technology, and the assembled genome reported here is 3,234,770 bp, with a GC content of 49.41%., The halophilic bacterium Salinivibrio sp. strain EAGSL was isolated from the Great Salt Lake (Utah) for use in microbial electrochemical technologies experiencing fluctuating salt concentrations. Genome sequencing was performed with Ion Torrent technology, and the assembled genome reported here is 3,234,770 bp with a GC content of 49.41%.

The moderate halophile Alkalicoccus halolimnae BZ-SZ-XJ29 T grows optimally in a relative broad range of 8.3% to 12.3% (wt/vol) NaCl. The draft genome consists of approximately 3.66 Mb and contains 3,534 putative genes. Various genes involved in osmotic stress were predicted, providing pertinent insights into specific adaptations to the hypersaline environment.

The whole-genome shotgun sequence of a moderately halophilic bacterium, Halomonas sp. strain SBS 10, was assembled and studied. The assembled genome size was 1.5 Mb, with a G+C content of 63.6%. The genome sequence of this Halomonas sp. SBS 10 isolate will be valuable in understanding gene clusters and functions involved in the adaptability of this bacterium to hypersaline conditions.

Two extremely halophilic archaea, namely, Natrinema versiforme BOL5-4 and Natrinema pallidum BOL6-1, were isolated from a Bolivian salt mine and their genomes sequenced using single-molecule real-time sequencing. The GC-rich genomes of BOL5-4 and BOL6-1 were 4.6 and 3.8 Mbp, respectively, with large chromosomes and multiple megaplasmids. Genome annotation was incorporated into HaloWeb and methylation patterns incorporated into REBASE.

In polyextremophiles, i.e., microorganisms growing preferentially under multiple extremes, synergistic effects may allow growth when application of the same extremes alone would not. High hydrostatic pressure (HP) is rarely considered in studies of polyextremophiles, and its role in potentially enhancing tolerance to other extremes remains unclear. Here, we investigated the HP-temperature response in Clostridium paradoxum, a haloalkaliphilic moderately thermophilic endospore-forming bacterium, in the range of 50 to 70°C and 0.1 to 30 MPa. At ambient pressure, growth limits were extended from the previously reported 63°C to 70°C, defining C. paradoxum as an actual thermophile. Concomitant application of high HP and temperature compared to standard conditions (i.e., ambient pressure and 50°C) remarkably enhanced growth, with an optimum growth rate observed at 22 MPa and 60°C. HP distinctively defined C. paradoxum physiology, as at 22 MPa biomass, production increased by 75% and the release of fermentation products per cell decreased by >50% compared to ambient pressure. This metabolic modulation was apparently linked to an energy-preserving mechanism triggered by HP, involving a shift toward pyruvate as the preferred energy and carbon source. High HPs decreased cell damage, as determined by Syto9 and propidium iodide staining, despite no organic solute being accumulated intracellularly. A distinct reduction in carbon chain length of phospholipid fatty acids (PLFAs) and an increase in the amount of branched-chain PLFAs occurred at high HP. Our results describe a multifaceted, cause-and-effect relationship between HP and cell metabolism, stressing the importance of applying HP to define the boundaries for life under polyextreme conditions. IMPORTANCE Hydrostatic pressure (HP) is a fundamental parameter influencing biochemical reactions and cell physiology; however, it is less frequently applied than other factors, such as pH, temperature, and salinity, when studying polyextremophilic microorganisms. In particular, how HP affects microbial tolerance to other and multiple extremes remains unclear. Here, we show that under polyextreme conditions of high pH and temperature, Clostridium paradoxum demonstrates a moderately piezophilic nature as cultures grow to highest cell densities and most efficiently at a specific combination of temperature and HP. Our results highlight the importance of considering HP when exploring microbial physiology under extreme conditions and thus have implications for defining the limits for microbial life in nature and for optimizing industrial bioprocesses occurring under multiple extremes.

We isolated halophilic and thermophilic Thermus thermophilus strains AA2-20 and AA2-29 from nonvolcanic, oceanic Arima Onsen (hot spring) in Japan. Here, we report the complete genome sequences of these organisms to gain insights into halophilicity.

Lentibacillus salicampi SF-20T (=ATCC BAA-719T) was first isolated from a Yellow Sea salt field in Korea in 2002. Here, we report that the L. salicampi ATCC BAA-719T genome sequence has a predicted length of 3,897,716 bp, containing 3,945 total genes and a CRISPR array, with a G+C content of 43.0%.

Here, we report the complete genome sequence of Halomonas olivaria strain TYRC17, a moderately halophilic, Gram-negative bacterium that was isolated from olive processing effluents. The 5-Mbp genome consists of 7,375 protein-coding sequences, including a variety of genes involved in tyrosol metabolism, nitrate respiration, and the production of polysaccharides.

We report here the genome sequence of halophilic Halobacillus trueperi SS1, isolated from the Lunsu saltwater body in India. The bacteria are Gram positive and rod shaped., We report here the genome sequence of halophilic Halobacillus trueperi SS1, isolated from the Lunsu saltwater body in India. The bacteria are Gram positive and rod shaped. The genome of H. trueperi SS1 has 4.14 Mbp, with 4,329 coding sequences, 35 RNA genes (29 tRNAs, 2 rRNAs, and 4 noncoding RNAs), and 42.15% G+C content.

Halocella sp. strain SP3-1, a cellulose-degrading bacterium, was isolated from a hypersaline evaporation pond in Thailand. Here, we report the first complete genome sequence of strain SP3-1. This species has a genome size of 4,035,760 bases, and the genome contains several genes encoding cellulose, hemicellulose, starch-degrading enzymes, and bacteriocins.

Deep Lake in the Vestfold Hills is hypersaline and the coldest system in Antarctica known to support microbial growth (temperatures as low as −20°C). It represents a strong experimental model because the lake supports a low-complexity community of haloarchaea, with the three most abundant species totaling ∼72%. Moreover, the dominant haloarchaea are cultivatable, and their genomes are sequenced. Here we use metaproteomics linked to metagenome data and the genome sequences of the isolates to characterize the main pathways, trophic strategies, and interactions associated with resource utilization. The dominance of the most abundant member, Halohasta litchfieldiae , appears to be predicated on competitive utilization of substrates (e.g., starch, glycerol, and dihydroxyacetone) produced by Dunaliella , the lake's primary producer, while also possessing diverse mechanisms for acquiring nitrogen and phosphorus. The second most abundant member, strain DL31, is proficient in degrading complex proteinaceous matter. Hht. litchfieldiae and DL31 are inferred to release labile substrates that are utilized by Halorubrum lacusprofundi , the third most abundant haloarchaeon in Deep Lake. The study also linked genome variation to specific protein variants or distinct genetic capacities, thereby identifying strain-level variation indicative of specialization. Overall, metaproteomics revealed that rather than functional differences occurring at different lake depths or through size partitioning, the main lake genera possess major trophic distinctions, and phylotypes (e.g., strains of Hht. litchfieldiae ) exhibit a more subtle level of specialization. This study highlights the extent to which the lake supports a relatively uniform distribution of taxa that collectively possess the genetic capacity to effectively exploit available nutrients throughout the lake. IMPORTANCE Life on Earth has evolved to colonize a broad range of temperatures, but most of the biosphere (∼85%) exists at low temperatures (≤5°C). By performing unique roles in biogeochemical cycles, environmental microorganisms perform functions that are critical for the rest of life on Earth to survive. Cold environments therefore make a particularly important contribution to maintaining healthy, stable ecosystems. Here we describe the main physiological traits of the dominant microorganisms that inhabit Deep Lake in Antarctica, the coldest aquatic environment known to support life. The hypersaline system enables the growth of halophilic members of the Archaea : haloarchaea. By analyzing proteins of samples collected from the water column, we determined the functions that the haloarchaea were likely to perform. This study showed that the dominant haloarchaea possessed distinct lifestyles yet formed a uniform community throughout the lake that was collectively adept at using available light energy and diverse organic substrates for growth.

Halomonas elongata strain MH25661, a moderate halophile, was isolated from a saline creek in the Andes of Peru. Genome annotation analyses revealed genes that respond to osmotic stress and oxidative stress, genes that are involved in sporulation, and genes that are involved in transport systems and resistance to antibiotics and toxic compounds.

Halomonas sp. strain SL1, a halophilic gammaproteobacterium, was isolated from samples from the Great Salt Lake in Utah. We report here the draft genome sequence of SL1, which has an estimated total sequence length of 3.6 Mb.

Here, we report the genome sequence of hyperthermophilic and halophilic Parageobacillus toebii PW12, isolated from the Tattapani hot spring in the northwest Himalayas. The genome size of Parageobacillus toebii PW12 is 3,210,377 bp., Here, we report the genome sequence of hyperthermophilic and halophilic Parageobacillus toebii PW12, isolated from the Tattapani hot spring in the northwest Himalayas. The genome size of Parageobacillus toebii PW12 is 3,210,377 bp. The G+C content is 42.05%, and 3,382 coding sequences (CDS), 80 tRNAs, 5 noncoding RNAs (ncRNAs), and 4 CRISPR arrays were predicted.

Bacillus salarius IM0101 is a halophilic bacterium that was isolated from soil in Inner Mongolia, China. The genome sequence of B. salarius IM0101 contains a biomarker gene for polyhydroxyalkanoate (PHA) synthesis., Bacillus salarius IM0101 is a halophilic bacterium that was isolated from soil in Inner Mongolia, China. The genome sequence of B. salarius IM0101 contains a biomarker gene for polyhydroxyalkanoate (PHA) synthesis. This 6.9-Mb draft genome sequence of B. salarius IM0101 will provide new insights into the organism’s PHA production machinery.

Vibrio alginolyticus is a Gram-negative halophilic and mesophilic bacterium, particularly associated with severe epidemic vibriosis, which causes high mortality in marine animals, including fish, shellfish, and shrimp ([1][1]). The carbapenemase NDM-1 has been found mainly in Enterobacteriaceae

Many Arcobacter spp. are free living and are routinely recovered from marine environments., Many Arcobacter spp. are free living and are routinely recovered from marine environments. Arcobacter halophilus was isolated from hypersaline lagoon water in the Hawaiian islands, and it was demonstrated to be an obligate halophile. This study describes the complete whole-genome sequence of the A. halophilus type strain, CCUG 53805 (= LA31BT = ATCC BAA-1022T).

The halophilic, alkaliphilic bacterium Bacillus sp. strain YSP-3 was isolated from a salt lake., The halophilic, alkaliphilic bacterium Bacillus sp. strain YSP-3 was isolated from a salt lake. It grows optimally at 8% (wt/vol) NaCl (pH 9.0). The draft genome is composed of 4,006 predicted genes. Genomic analysis showed that various genes are potentially involved in the adaptation mechanisms for osmotic stress and pH homeostasis.

The aerobic halophilic bacterium Halomonas urumqiensis BZ-SZ-XJ27 T , growing optimally at 1.42 M Na + , with a range of 0.22 to 4.32 M Na + , was isolated from a salt lake in the Xinjiang Uyghur Autonomous Region of China. Here, we report the draft genome sequence of strain BZ-SZ-XJ27 T , which consists of approximately 3.97 Mb and contains 3,588 predicted genes.

The complete genome sequence of Cyanobacterium sp. strain HL-69 consists of 3,155,247 bp and contains 2,897 predicted genes comprising a chromosome and two plasmids. The genome is consistent with a halophilic nondiazotrophic phototrophic lifestyle, and this organism is able to synthesize most B vitamins and produces several secondary metabolites.

Aquaglyceroporins (GlpFs) that transport glycerol along with water and other uncharged solutes are involved in osmoregulation in myriad species. Fungal species form a large group of eukaryotic organisms, and their GlpFs may be diverse, exhibiting various activities. However, few filamentous fungal GlpFs have been biologically investigated. Here, a glpF gene from the halophilic fungus Aspergillus glaucus ( AgglpF ) was verified to be a channel of water or glycerol in Xenopus laevis oocytes and was further functionally analyzed in three heterologous systems. In Saccharomyces cerevisiae , cells overexpressing AgglpF possessed significant tolerance of drought, salt, and certain metal ions. AgglpF was then characterized in the filamentous fungus of Neurospora crassa . Based on the N. crassa aquaporin gene ( NcAQP ) disruption mutant (the Δ aqp mutant), a series of complementary strains carrying NcAQP and AgglpF and three asparagine-proline-alanine-gene ( NPA )-deleted AgglpF fragments were created. As revealed by salt resistance analysis, the AgglpF complementary strain possessed the highest salt resistance among the tested strains. In addition, the intracellular glycerol content in the AgglpF complementary strain was markedly higher than that in the other strains. The AgGlpF-green fluorescent protein (GFP) fusion protein was subcellularly localized in the plasma membrane of onion epidermal cells, suggesting that AgglpF functions in plants. Indeed, when AgglpF was expressed in Arabidopsis thaliana , transgenic lines survived under conditions of high osmotic stress and under conditions of drought stress in particular. Overall, our results revealed that AgGlpF as a water/glycerol transporter is required for survival of both fungi and plants under conditions of high osmotic stress and may have value in applications in genetic engineering for generating high salt and drought resistance.

Anaerobic oxidation of methane (AOM) coupled to nitrite reduction is a novel AOM process that is mediated by denitrifying methanotrophs. To date, enrichments of these denitrifying methanotrophs have been confined to freshwater systems; however, the recent findings of 16S rRNA and pmoA gene sequences in marine sediments suggest a possible occurrence of AOM coupled to nitrite reduction in marine systems. In this research, a marine denitrifying methanotrophic culture was obtained after 20 months of enrichment. Activity testing and quantitative PCR (qPCR) analysis were then conducted and showed that the methane oxidation activity and the number of NC10 bacteria increased correlatively during the enrichment period. 16S rRNA gene sequencing indicated that only bacteria in group A of the NC10 phylum were enriched and responsible for the resulting methane oxidation activity, although a diverse community of NC10 bacteria was harbored in the inoculum. Fluorescence in situ hybridization showed that NC10 bacteria were dominant in the enrichment culture after 20 months. The effect of salinity on the marine denitrifying methanotrophic culture was investigated, and the apparent optimal salinity was 20.5‰, which suggested that halophilic bacterial AOM coupled to nitrite reduction was obtained. Moreover, the apparent substrate affinity coefficients of the halophilic denitrifying methanotrophs were determined to be 9.8 ± 2.2 μM for methane and 8.7 ± 1.5 μM for nitrite.

Cell motility in pure cultures of halophilic archaea was first observed almost a century ago and, in methanogens, at least as long ago as 1951, when Methanococcus vannielii was first isolated. Although M. vannielii was reported as being motile, no flagella were observed until nearly three decades later. Other researchers from that era reported seeing fimbriae (pili) or flagella on a variety of different archaea, including methanogens, halophiles, and Sulfolobus. However, during that period the members of the archaea were still considered bacteria, predating the groundbreaking realignment of the tree of life into the three domains of Archaea, Bacteria, and Eukarya by Carl Woese.

We examined the diversity and community structure of members of the halophilic Archaea (class Halobacteria ) in samples from central and southern Tunisian endorheic salt lakes and sebkhet (also known as sebkha) systems using targeted 16S rRNA gene diversity survey and quantitative PCR (qPCR) approaches. Twenty-three different samples from four distinct locations exhibiting a wide range of salinities (2% to 37%) and physical characteristics (water, salt crust, sediment, and biofilm) were examined. A total of 4,759 operational taxonomic units at the 0.03 (species-level) cutoff (OTU 0.03 s) belonging to 45 currently recognized genera were identified, with 8 to 43 genera (average, 30) identified per sample. In spite of the large number of genera detected per sample, only a limited number (i.e., 2 to 16) usually constituted the majority (≥80%) of encountered sequences. Halobacteria diversity showed a strong negative correlation to salinity (Pearson correlation coefficient = −0.92), and community structure analysis identified salinity, rather than the location or physical characteristics of the sample, as the most important factor shaping the Halobacteria community structure. The relative abundance of genera capable of biosynthesis of the compatible solute(s) trehalose or 2-sulfotrehalose decreased with increasing salinities (Pearson correlation coefficient = −0.80). Indeed, qPCR analysis demonstrated that the Halobacteria otsB (trehalose-6-phosphatase)/16S rRNA gene ratio decreases with increasing salinities (Pearson correlation coefficient = −0.87). The results highlight patterns and determinants of Halobacteria diversity at a previously unexplored ecosystem and indicate that genera lacking trehalose biosynthetic capabilities are more adapted to growth in and colonization of hypersaline (>25% salt) ecosystems than trehalose producers.

Lake Vanda is a perennially ice-covered and stratified lake in the McMurdo Dry Valleys, Antarctica. The lake develops a distinct chemocline at about a 50-m depth, where the waters transition from cool, oxic, and fresh to warm, sulfidic, and hypersaline. The bottom water brine is unique, as the highly chaotropic salts CaCl 2 and MgCl 2 predominate, and CaCl 2 levels are the highest of those in any known microbial habitat. Enrichment techniques were used to isolate 15 strains of heterotrophic bacteria from the Lake Vanda brine. Despite direct supplementation of the brine samples with different organic substrates in primary enrichments, the same organism, a relative of the halophilic bacterium Halomonas ( Gammaproteobacteria ), was isolated from all depths sampled. The Lake Vanda (VAN) strains were obligate aerobes and showed broad pH, salinity, and temperature ranges for growth, consistent with the physicochemical properties of the brine. VAN strains were halophilic and quite CaCl 2 tolerant but did not require CaCl 2 for growth. The fact that only VAN strain-like organisms appeared in our enrichments hints that the highly chaotropic nature of the Lake Vanda brine may place unusual physiological constraints on the bacterial community that inhabits it.

Haloarcula japonica, an extremely halophilic archaeon that requires high concentrations of NaCl for growth, accumulates the C50carotenoid bacterioruberin (BR). By homology analysis, a gene cluster, includingc0507,c0506, andc0505, was found and predicted to be involved in the synthesis of bacterioruberin. To elucidate the function of the encoded enzymes, we constructedHa. japonicamutants of these genes and analyzed carotenoids produced by the mutants. Our research showed thatc0507,c0506, andc0505encoded a carotenoid 3,4-desaturase (CrtD), a bifunctional lycopene elongase and 1,2-hydratase (LyeJ), and a C50carotenoid 2″,3″-hydratase (CruF), respectively. The above three carotenoid biosynthetic enzymes catalyze the reactions that convert lycopene to bacterioruberin inHa. japonica. This is the first identification of functional CrtD and CruF in archaea and elucidation of the complete biosynthetic pathway of bacterioruberin from lycopene.IMPORTANCEHaloarcula japonica, an extremely halophilic archaeon, accumulates the C50carotenoid bacterioruberin (BR). In this study, we have identified three BR biosynthetic enzymes and have elucidated their functions. Among them, two enzymes were found in an archaeon for the first time. Our results revealed the biosynthetic pathway responsible for production of BR inHa. japonicaand provide a basis for investigating carotenoid biosynthetic pathways in other extremely halophilic archaea. Elucidation of the carotenoid biosynthetic pathway inHa. japonicamay also prove useful for producing the C50carotenoid BR efficiently by employing genetically modified haloarchaeal strains.

Vibrio parahaemolyticus is a halophile that is the predominant cause of bacterial seafood-related gastroenteritis worldwide. To survive in the marine environment, V. parahaemolyticus must have adaptive strategies to cope with salinity changes. Six putative compatible solute (CS) transport systems were previously predicted from the genome sequence of V. parahaemolyticus RIMD2210633. In this study, we determined the role of the four putative betaine-carnitine-choline transporter (BCCT) homologues VP1456, VP1723, VP1905, and VPA0356 in the NaCl stress response. Expression analysis of the four BCCTs subjected to NaCl upshock showed that VP1456, VP1905, and VPA0356, but not VP1723, were induced. We constructed in-frame single-deletion mutant strains for all four BCCTs, all of which behaved similarly to the wild-type strain, demonstrating a redundancy of the systems. Growth analysis of a quadruple mutant and four BCCT triple mutants demonstrated the requirement for at least one BCCT for efficient CS uptake. We complemented Escherichia coli MHK13, a CS synthesis- and transporter-negative strain, with each BCCT and examined CS uptake by growth analysis and 1 H nuclear magnetic resonance (NMR) spectroscopy analyses. These data demonstrated that VP1456 had the most diverse substrate transport ability, taking up glycine betaine (GB), proline, choline, and ectoine. VP1456 was the sole ectoine transporter. In addition, the data demonstrated that VP1723 can transport GB, proline, and choline, whereas VP1905 and VPA0356 transported only GB. Overall, the data showed that the BCCTs are functional and that there is redundancy among them.

The halotolerant alga Dunaliella salina is a model for stress tolerance and is used commercially for production of beta-carotene (=pro-vitamin A). The presented draft genome of the genuine strain CCAP19/18 will allow investigations into metabolic processes involved in regulation of stress responses, including carotenogenesis and adaptations to life in high-salinity environments.

Hahella sp. strain CCB-MM4 is a halophilic bacterium isolated from estuarine mangrove sediment. The genome sequence of Hahella sp. CCB-MM4 provides insights into exopolysaccharide biosynthesis and the lifestyle of the bacterium thriving in a saline mangrove environment.

Here, we report the draft genome sequence of Rubricoccus marinus SG-29 T , a bacterium isolated from the western North Pacific Ocean. R. marinus SG-29 T possesses two different types of rhodopsin genes and belongs to the family Rhodothermaceae , with which halophilic, thermophilic, and marine bacteria are associated.

Halotolerant enzymes are beneficial for industrial processes requiring high salt concentrations and low water activity. Most halophilic proteins are evolved to have reduced hydrophobic interactions on the surface and in the hydrophobic cores for their haloadaptation. However, in this study, we improved the halotolerance of a thermolabile esterase, E40, by increasing intraprotein hydrophobic interactions. E40 was quite unstable in buffers containing more than 0.3 M NaCl, and its k cat and substrate affinity were both significantly reduced in 0.5 M NaCl. By introducing hydrophobic residues in loop 1 of the CAP domain and/or α7 of the catalytic domain in E40, we obtained several mutants with improved halotolerance, and the M3 S202W I203F mutant was the most halotolerant. (“M3” represents a mutation in loop 1 of the CAP domain in which residues R22-K23-T24 of E40 are replaced by residues Y22-K23-H24-L25-S26 of Est2.) Then we solved the crystal structures of the S202W I203F and M3 S202W I203F mutants to reveal the structural basis for their improved halotolerance. Structural analysis revealed that the introduction of hydrophobic residues W202 and F203 in α7 significantly improved E40 halotolerance by strengthening intradomain hydrophobic interactions of F203 with W202 and other residues in the catalytic domain. By further introducing hydrophobic residues in loop 1, the M3 S202W I203F mutant became more rigid and halotolerant due to the formation of additional interdomain hydrophobic interactions between the introduced Y22 in loop 1 and W204 in α7. These results indicate that increasing intraprotein hydrophobic interactions is also a way to improve the halotolerance of enzymes with industrial potential under high-salt conditions. IMPORTANCE Esterases and lipases for industrial application are often subjected to harsh conditions such as high salt concentrations, low water activity, and the presence of organic solvents. However, reports on halotolerant esterases and lipases are limited, and the underlying mechanism for their halotolerance is still unclear due to the lack of structures. In this study, we focused on the improvement of the halotolerance of a salt-sensitive esterase, E40, and the underlying mechanism. The halotolerance of E40 was significantly improved by introducing hydrophobic residues. Comparative structural analysis of E40 and its halotolerant mutants revealed that increased intraprotein hydrophobic interactions make these mutants more rigid and more stable than the wild type against high concentrations of salts. This study shows a new way to improve enzyme halotolerance, which is helpful for protein engineering of salt-sensitive enzymes.

The anaerobic, halophilic, alkaliphilic, thermotolerant bacterium Natranaerobius trueperi was isolated from a soda lake in Wadi An Natrun, Egypt. It grows optimally at 3.7 M Na + , pH 9.5, and 43°C. The draft genome consists of 2.63 Mb and is composed of 2,681 predicted genes. Genomic analysis showed that various genes are potentially involved in the adaptation mechanisms for osmotic stress, pH homeostasis, and high temperatures.

Pseudoalteromonas piscicida strain DE2-B is a halophilic bacterium which has broad inhibitory activity toward vibrios and other human and fish pathogens. We report the first closed genome sequence for this species, which consists of two chromosomes (4,128,210 and 1,188,838 bp). Annotation revealed multiple genes encoding proteases with potential antibacterial properties.

A draft genome sequence of a neutrophilic halophile capable of thiocyanate degradation, Thiohalobacter thiocyanaticus FOKN1, was determined using a PacBio RSII sequencer. A 3.23-Mb circular genome sequence was assembled, in which 3,026 gene-coding sequences, 45 tRNAs, and 1 rrn operon were annotated.

The draft genome sequences of 5 type strains of species of the halophilic genus Salinivibrio and 29 new isolates from different hypersaline habitats belonging to the genus Salinivibrio have been determined. The genomes have 3,123,148 to 3,641,359 bp, a G+C content of 49.2 to 50.9%, and 2,898 to 3,404 open reading frames (ORFs).

Tetragenococcus muriaticus strains 3MR10-3 and PMC-11-5 are homofermentative halophilic lactic acid bacteria isolated from Thai fish sauce during natural fermentation. Their draft genomes were sequenced. Our interest in these organisms is related to their impact on fish sauce flavor and their high osmotolerance.

The complete genome sequence of Methanohalophilus halophilus DSM 3094 T , a member of the Methanosarcinaceae family and the Methanosarcianales order, consists of 2,022,959 bp in one contig and contains 2,137 predicted genes. The genome is consistent with a halophilic methylotrophic anaerobic lifestyle, including the methylotrophic and CO 2 -H 2 methanogensis pathways.

Halolamina pelagica strain CDK2, a halophilic archaeon (growth range 1.36 to 5.12 M NaCl), was isolated from rhizosphere of wild grasses of hypersaline soil of the Rann of Kutch, Gujarat, India. Its draft genome contains 2,972,542 bp and 3,485 coding sequences, depicting genes for halophilic serine proteases and trehalose synthesis.

Recent metagenomic studies on saltern ponds with intermediate salinities have determined that their microbial communities are dominated by both Euryarchaeota and halophilic bacteria, with a gammaproteobacterium closely related to the genera Alkalilimnicola and Arhodomonas being one of the most predominant microorganisms, making up to 15% of the total prokaryotic population. Here we used several strategies and culture media in order to isolate this organism in pure culture. We report the isolation and taxonomic characterization of this new, never before cultured microorganism, designated M19-40 T , isolated from a saltern located in Isla Cristina, Spain, using a medium with a mixture of 15% salts, yeast extract, and pyruvic acid as the carbon source. Morphologically small curved cells (young cultures) with a tendency to form long spiral cells in older cultures were observed in pure cultures. The organism is a Gram-negative, nonmotile bacterium that is strictly aerobic, non-endospore forming, heterotrophic, and moderately halophilic, and it is able to grow at 10 to 25% (wt/vol) NaCl, with optimal growth occurring at 15% (wt/vol) NaCl. Phylogenetic analysis based on 16S rRNA gene sequence comparison showed that strain M19-40 T has a low similarity with other previously described bacteria and shows the closest phylogenetic similarity with species of the genera Alkalilimnicola (94.9 to 94.5%), Alkalispirillum (94.3%), and Arhodomonas (93.9%) within the family Ectothiorhodospiraceae . The phenotypic, genotypic, and chemotaxonomic features of this new bacterium showed that it constitutes a new genus and species, for which the name Spiribacter salinus gen. nov., sp. nov., is proposed, with strain M19-40 T (= CECT 8282 T = IBRC-M 10768 T = LMG 27464 T ) being the type strain.

Wallemia ichthyophaga is a fungus from the ancient basidiomycetous genus Wallemia (Wallemiales, Wallemiomycetes) that grows only at salinities between 10% (wt/vol) NaCl and saturated NaCl solution. This obligate halophily is unique among fungi. The main goal of this study was to determine the optimal salinity range for growth of the halophilic W. ichthyophaga and to unravel its osmoadaptation strategy. Our results showed that growth on solid growth media was extremely slow and resulted in small colonies. On the other hand, in the liquid batch cultures, the specific growth rates of W. ichthyophaga were higher, and the biomass production increased with increasing salinities. The optimum salinity range for growth of W. ichthyophaga was between 15 and 20% (wt/vol) NaCl. At 10% NaCl, the biomass production and the growth rate were by far the lowest among all tested salinities. Furthermore, the cell wall content in the dry biomass was extremely high at salinities above 10%. Our results also showed that glycerol was the major osmotically regulated solute, since its accumulation increased with salinity and was diminished by hypo-osmotic shock. Besides glycerol, smaller amounts of arabitol and trace amounts of mannitol were also detected. In addition, W. ichthyophaga maintained relatively small intracellular amounts of potassium and sodium at constant salinities, but during hyperosmotic shock, the amounts of both cations increased significantly. Given our results and the recent availability of the genome sequence, W. ichthyophaga should become well established as a novel model organism for studies of halophily in eukaryotes.