Microbial Iron Oxidation in the Arctic Tundra and Its Implications for Biogeochemical Cycling

ABSTRACTThe role that neutrophilic iron-oxidizing bacteria play in the Arctic tundra is unknown. This study surveyed chemosynthetic iron-oxidizing communities at the North Slope of Alaska near Toolik Field Station (TFS) at Toolik Lake (lat 68.63, long −149.60). Microbial iron mats were common in submerged habitats with stationary or slowly flowing water, and their greatest areal extent is in coating plant stems and sediments in wet sedge meadows. Some Fe-oxidizing bacteria (FeOB) produce easily recognized sheath or stalk morphotypes that were present and dominant in all the mats we observed. The cool water temperatures (9 to 11°C) and reduced pH (5.0 to 6.6) at all sites kinetically favor microbial iron oxidation. A microbial survey of five sites based on 16S rRNA genes found a predominance ofProteobacteria, withBetaproteobacteriaand members of the familyComamonadaceaebeing the most prevalent operational taxonomic units (OTUs). In relative abundance, clades of lithotrophic FeOB composed 5 to 10% of the communities. OTUs related to cyanobacteria and chloroplasts accounted for 3 to 25% of the communities. Oxygen profiles showed evidence for oxygenic photosynthesis at the surface of some mats, indicating the coexistence of photosynthetic and FeOB populations. The relative abundance of OTUs belonging to putative Fe-reducing bacteria (FeRB) averaged around 11% in the sampled iron mats. Mats incubated anaerobically with 10 mM acetate rapidly initiated Fe reduction, indicating that active iron cycling is likely. The prevalence of iron mats on the tundra might impact the carbon cycle through lithoautotrophic chemosynthesis, anaerobic respiration of organic carbon coupled to iron reduction, and the suppression of methanogenesis, and it potentially influences phosphorus dynamics through the adsorption of phosphorus to iron oxides.

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Microbial Infections Are Associated with Embryo Mortality in Arctic-Nesting Geese

Applied and Environmental Microbiology ◽

10.1128/aem.00706-15 ◽

2015 ◽

Vol 81 (16) ◽

pp. 5583-5592 ◽

Cited By ~ 14

Author(s):

Cristina M. Hansen ◽

Brandt W. Meixell ◽

Caroline Van Hemert ◽

Rebekah F. Hare ◽

Karsten Hueffer

Keyword(s):

Bacterial Infections ◽

Bacterial Species ◽

Breeding Population ◽

16S Rrna Genes ◽

The Arctic ◽

Rrna Genes ◽

Culture Methods ◽

Embryo Mortality ◽

Content Type ◽

Streptococcus Uberis

ABSTRACTTo address the role of bacterial infection in hatching failure of wild geese, we monitored embryo development in a breeding population of Greater white-fronted geese (Anser albifrons) on the Arctic Coastal Plain of Alaska. During 2013, we observed mortality of normally developing embryos and collected 36 addled eggs for analysis. We also collected 17 infertile eggs for comparison. Using standard culture methods and gene sequencing to identify bacteria within collected eggs, we identified a potentially novel species ofNeisseriain 33 eggs,Macrococcus caseolyticusin 6 eggs, andStreptococcus uberisandRothia nasimuriumin 4 eggs each. We detected seven other bacterial species at lower frequencies. Sequences of the 16S rRNA genes from theNeisseriaisolates most closely matched sequences fromN. animalorisandN. canis(96 to 97% identity), but phylogenetic analysis suggested substantial genetic differentiation between egg isolates and knownNeisseriaspecies. Although definitive sources of the bacteria remain unknown, we detectedNeisseriaDNA from swabs of eggshells, nest contents, and cloacae of nesting females. To assess the pathogenicity of bacteria identified in contents of addled eggs, we inoculated isolates ofNeisseria,Macrococcus,Streptococcus, andRothiaat various concentrations into developing chicken eggs. Seven-day mortality rates varied from 70 to 100%, depending on the bacterial species and inoculation dose. Our results suggest that bacterial infections are a source of embryo mortality in wild geese in the Arctic.

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Seasonal and spatial variations in microbial activity at various phylogenetic resolutions at a groundwater – surface water interface

Canadian Journal of Microbiology ◽

10.1139/cjm-2014-0048 ◽

2014 ◽

Vol 60 (5) ◽

pp. 277-286 ◽

Cited By ~ 1

Author(s):

Ran Yu ◽

Barth F. Smets ◽

Ping Gan ◽

Allison A. MacKay ◽

Joerg Graf

Keyword(s):

Surface Water ◽

16S Rrna ◽

Microbial Activity ◽

Clone Library ◽

Iron Oxidation ◽

16S Rrna Genes ◽

Rrna Genes ◽

Water Interface ◽

Microbial Activities ◽

Microbial Iron Oxidation

We investigated the seasonal and spatial variation in activity and density of the metabolically active in situ microbial community (AIMC) at a landfill leachate-impacted groundwater – surface water interface (GSI). A series of AIMC traps were designed and implemented for AIMC sampling and microbial activity and density examinations. Measurements were made not only at the level of bacterial domain but also at the levels of alphaproteobacterial Rhizobiales order and gammaproteobacterial Pseudomonas genus, both of which included a large number of iron-oxidizing bacteria as revealed from previous analysis. Consistently higher microbial activities with less variation in depth were measured in the AIMC traps than in the ambient sediments. Flood disturbance appeared to control AIMC activity distributions at the gradually elevated GSI. The highest AIMC activities were generally obtained from locations closest to the free surface water boundary except during the dry season when microbial activities were similar across the entire GSI. A clone library of AIMC 16S rRNA genes was constructed, and it confirmed the predominant role of the targeted alphaproteobacterial group in AIMC activity and composition. This taxon constituted 2%–14% of all bacteria with similar activity distribution profiles. The Pseudomonas group occupied only 0.1‰–0.5‰ of the total bacterial density, but its activity was 27 times higher than the bacterial average. Of the 16S rRNA sequences in the AIMC clone library, 7.5% were phylogenetically related to putative IOB, supporting the occurrence and persistence of active microbial iron oxidation across the studied iron-rich GSI ecosystem.

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Effects of Supplement of Marichromatium gracile YL28 on Water Quality and Microbial Structures in Shrimp Mariculture Ecosystems

Genes ◽

10.3390/genes12010040 ◽

2020 ◽

Vol 12 (1) ◽

pp. 40

Author(s):

Liang Cui ◽

Bitong Zhu ◽

Xiaobo Zhang ◽

Zhuhua Chan ◽

Chungui Zhao ◽

...

Keyword(s):

Water Quality ◽

16S Rrna ◽

Relative Abundance ◽

Animal Health ◽

Denitrifying Bacteria ◽

Nitrite Reduction ◽

16S Rrna Genes ◽

Rrna Genes ◽

Sequencing Analysis ◽

Shrimp Culture

The elevated NH3-N and NO2-N pollution problems in mariculture have raised concerns because they pose threats to animal health and coastal and offshore environments. Supplement of Marichromatium gracile YL28 (YL28) into polluted shrimp rearing water and sediment significantly decreased ammonia and nitrite concentrations, showing that YL28 functioned as a novel safe marine probiotic in the shrimp culture industry. The diversity of aquatic bacteria in the shrimp mariculture ecosystems was studied by sequencing the V4 region of 16S rRNA genes, with respect to additions of YL28 at the low and high concentrations. It was revealed by 16S rRNA sequencing analysis that Proteobacteria, Planctomycete and Bacteroidetes dominated the community (>80% of operational taxonomic units (OTUs)). Up to 41.6% of the predominant bacterial members were placed in the classes Gammaproteobacteria (14%), Deltaproteobacteria (14%), Planctomycetacia (8%) and Alphaproteobacteria (5.6%) while 40% of OTUs belonged to unclassified ones or others, indicating that the considerable bacterial populations were novel in our shrimp mariculture. Bacterial communities were similar between YL28 supplements and control groups (without addition of YL28) revealed by the β-diversity using PCoA, demonstrating that the additions of YL28 did not disturb the microbiota in shrimp mariculture ecosystems. Instead, the addition of YL28 increased the relative abundance of ammonia-oxidizing and denitrifying bacteria. The quantitative PCR analysis further showed that key genes including nifH and amoA involved in nitrification and nitrate or nitrite reduction significantly increased with YL28 supplementation (p < 0.05). The supplement of YL28 decreased the relative abundance of potential pathogen Vibrio. Together, our studies showed that supplement of YL28 improved the water quality by increasing the relative abundance of ammonia-oxidizing and denitrifying bacteria while the microbial community structure persisted in shrimp mariculture ecosystems.

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Comparative Analysis of the Fecal Bacterial Microbiota of Wintering Whooper Swans (Cygnus Cygnus)

Frontiers in Veterinary Science ◽

10.3389/fvets.2021.670645 ◽

2021 ◽

Vol 8 ◽

Author(s):

Wenxia Wang ◽

Songlin Huang ◽

Liangliang Yang ◽

Guogang Zhang

Keyword(s):

Intestinal Microbiota ◽

Relative Abundance ◽

High Throughput Sequencing ◽

The Body ◽

16S Rrna Genes ◽

Rrna Genes ◽

Illumina Hiseq ◽

Linear Discriminant ◽

Bacterial Microbiota ◽

And Control

There are many and diverse intestinal microbiota, and they are closely related to various physiological functions of the body. They directly participate in the host's food digestion, nutrient absorption, energy metabolism, immune response, and many other physiological activities and are also related to the occurrence of many diseases. The intestinal microbiota are extremely important for maintaining normal physical health. In order to explore the composition and differences of the intestinal microbiota of whooper swans in different wintering areas, we collected fecal samples of whooper swans in Sanmenxia, Henan, and Rongcheng, Shandong, and we used the Illumina HiSeq platform to perform high-throughput sequencing of bacterial 16S rRNA genes. Comparison between Sanmenxia and Rongcheng showed no significant differences in ACE, Chao 1, Simpson, and Shannon indices (p > 0.05). Beta diversity results showed significant differences in bacterial communities between two groups [analysis of similarity (ANOSIM): R = 0.80, p = 0.011]. Linear discriminant analysis effect size (LEfSe) analysis showed that at the phylum level, the relative abundance of Actinobacteria was significantly higher in Sanmenxia whooper swans than Rongcheng whooper swans. At the genus level, the amount of Psychrobacter and Carnobacterium in Sanmenxia was significantly higher in Rongcheng, while the relative abundance Catellicoccus and Lactobacillus was significantly higher in Rongcheng than in Sanmenxia. This study analyzed the composition, characteristics, and differences of the intestinal microbiota of the whooper swans in different wintering environments and provided theoretical support for further exploring the relationship between the intestinal microbiota of the whooper swans and the external environment. And it played an important role in the overwintering physiology and ecology, population management, and epidemic prevention and control of whooper swans.

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Characteristics of the vaginal microbiome in cross-border female sex workers in China: a case-control study

PeerJ ◽

10.7717/peerj.8131 ◽

2019 ◽

Vol 7 ◽

pp. e8131

Author(s):

Xiang Hong ◽

Shenghao Fang ◽

Kaiping Huang ◽

Jiechen Yin ◽

Jianshuang Chen ◽

...

Keyword(s):

Relative Abundance ◽

Sex Workers ◽

Female Sex Workers ◽

16S Rrna Genes ◽

Rrna Genes ◽

Health Examination ◽

Vaginal Microbiome ◽

Cross Border ◽

Female Sex ◽

Α Diversity

Background Female sex workers (FSWs) are key groups in the transmission of sexual transmitted infections (STI), and vaginal microbiome variations play an important role in transmission. We aimed to explore the characteristics of vaginal microbiome among FSWs. Materials and Methods A total of 24 cross-border FSWs were randomly selected from a cross-sectional survey for female sex workers in southwest China. Thirty-seven female non-sex workers (FNSWs) were randomly selected from the gynecology clinic and health examination center. Vaginal swabs were collected, bacterial DNA extracted and 16S rRNA genes were sequenced. Differences in the vaginal microbiome between both groups were compared using bioinformatics analysis. Results One DNA sample was excluded due to unqualified concentration, therefore 60 samples were sequenced. FSWs had significantly different vaginal microbiota β diversity, but undifferentiated α diversity when compared with non-sex workers. The average relative abundance of Sneathia, Shigella, Neisseria, Chlamydia, Prevotella, Enterococcus and Ureaplasma among FSWs was higher than FNSWs, and relative abundance of Atopobium in FSWs was lower than FNSWs. The Lactobacillus genus was the major genus in both groups. At the species level, Lactobacllus crispatus, Lactobacllus gasseri and Lactobacllus jensenii, in female sex workers, were lower when compared to FNSWs. Conclusion There were distinct differences in vaginal bacteria variety between FSWs and FNSWs. Some disease-related genus were also more abundant in FSWs. Based on these observations, further research is required to identify microbiome communities related to high STI risks and other diseases in these cohorts.

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Rhizobium azibense sp. nov., a nitrogen fixing bacterium isolated from root-nodules of Phaseolus vulgaris

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.058651-0 ◽

2014 ◽

Vol 64 (Pt_5) ◽

pp. 1501-1506 ◽

Cited By ~ 32

Author(s):

Bacem Mnasri ◽

Tian Yan Liu ◽

Sabrine Saidi ◽

Wen Feng Chen ◽

Wen Xin Chen ◽

...

Keyword(s):

Type Species ◽

Root Nodules ◽

16S Rrna Genes ◽

Rrna Genes ◽

The Novel ◽

Content Type ◽

Link Type ◽

Physiological Properties ◽

Microbial Strains ◽

Type Strains

Three microbial strains isolated from common beans, 23C2T (Tunisia), Gr42 (Spain) and IE4868 (Mexico), which have been identified previously as representing a genomic group closely related to Rhizobium gallicum , are further studied here. Their 16S rRNA genes showed 98.5–99 % similarity with Rhizobium loessense CCBAU 7190BT, R. gallicum R602spT, Rhizobium mongolense USDA 1844T and Rhizobium yanglingense CCBAU 71623T. Phylogenetic analysis based on recA, atpD, dnaK and thrC sequences showed that the novel strains were closely related and could be distinguished from the four type strains of the closely related species. Strains 23C2T, Gr42 and IE4868 could be also differentiated from their closest phylogenetic neighbours by their phenotypic and physiological properties and their fatty acid contents. All three strains harboured symbiotic genes specific to biovar gallicum. Levels of DNA–DNA relatedness between strain 23C2T and the type strains of R. loessense , R. mongolense , R. gallicum and R. yanglingense ranged from 58.1 to 61.5 %. The DNA G+C content of the genomic DNA of strain 23C2T was 59.52 %. On the basis of these data, strains 23C2T, Gr42 and IE4868 were considered to represent a novel species of the genus Rhizobium for which the name Rhizobium azibense is proposed. Strain 23C2T ( = CCBAU 101087T = HAMBI3541T) was designated as the type strain.

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Application of a Euryarchaeota-Specific Helicase from Thermococcus kodakarensis for Noise Reduction in PCR

Applied and Environmental Microbiology ◽

10.1128/aem.04116-15 ◽

2016 ◽

Vol 82 (10) ◽

pp. 3022-3031 ◽

Cited By ~ 8

Author(s):

Ayako Fujiwara ◽

Katsuhiro Kawato ◽

Saori Kato ◽

Kiyoshi Yasukawa ◽

Ryota Hidese ◽

...

Keyword(s):

Noise Reduction ◽

Dna Polymerase ◽

Biological Activities ◽

Genetic Diagnosis ◽

Gc Content ◽

Dna Amplification ◽

16S Rrna Genes ◽

Rrna Genes ◽

Content Type ◽

Thermococcus Kodakarensis

ABSTRACTDNA/RNA helicases, which are enzymes for eliminating hydrogen bonds between bases of DNA/DNA, DNA/RNA, and RNA/RNA using the energy of ATP hydrolysis, contribute to various biological activities. In the present study, theEuryarchaeota-specific helicase EshA (TK0566) from the hyperthermophilic archaeonThermococcus kodakarensis(Tk-EshA) was obtained as a recombinant form, and its enzymatic properties were examined.Tk-EshA exhibited maximal ATPase activity in the presence of RNA at 80°C. Unwinding activity was evaluated with various double-stranded DNAs (forked, 5′ overhung, 3′ overhung, and blunt end) at 50°C.Tk-EshA unwound forked and 3′ overhung DNAs. These activities were expected to unwind the structured template and to peel off misannealed primers whenTk-EshA was added to a PCR mixture. To examine the effect ofTk-EshA on PCR, various target DNAs were selected, and DNA synthesis was investigated. When 16S rRNA genes were used as a template, several misamplified products (noise DNAs) were detected in the absence ofTk-EshA. In contrast, noise DNAs were eliminated in the presence ofTk-EshA. Noise reduction byTk-EshA was also confirmed whenTaqDNA polymerase (a family A DNA polymerase, PolI type) and KOD DNA polymerase (a family B DNA polymerase, α type) were used for PCR. Misamplified bands were also eliminated duringtoxAgene amplification fromPseudomonas aeruginosaDNA, which possesses a high GC content (69%).Tk-EshA addition was more effective than increasing the annealing temperature to reduce misamplified DNAs duringtoxAamplification.Tk-EshA is a useful tool to reduce noise DNAs for accurate PCR.IMPORTANCEPCR is a technique that is useful for genetic diagnosis, genetic engineering, and detection of pathogenic microorganisms. However, troubles with nonspecific DNA amplification often occur from primer misannealing. In order to achieve a specific DNA amplification by eliminating noise DNAs derived from primer misannealing, a thermostableEuryarchaeota-specific helicase (Tk-EshA) was included in the PCR mixture. The addition ofTk-EshA has reduced noise DNAs in PCR.

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Alkalibacterium gilvum sp. nov., slightly halophilic and alkaliphilic lactic acid bacterium isolated from soft and semi-hard cheeses

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.042556-0 ◽

2013 ◽

Vol 63 (Pt_4) ◽

pp. 1471-1478 ◽

Cited By ~ 21

Author(s):

Morio Ishikawa ◽

Kazuhide Yamasato ◽

Kayo Kodama ◽

Hinako Yasuda ◽

Mioko Matsuyama ◽

...

Keyword(s):

Lactic Acid ◽

Sequence Similarity ◽

16S Rrna Genes ◽

Rrna Genes ◽

Molar Ratio ◽

Phylogenetic Position ◽

Growth Responses ◽

Cultivation Conditions ◽

Content Type ◽

Link Type

Nine novel strains of halophilic and alkaliphilic lactic acid bacteria isolated from European soft and semi-hard cheeses by using a saline, alkaline medium (7 % NaCl, pH 9.5) were taxonomically characterized. The isolates were Gram-stain-positive, non-sporulating and non-motile. They lacked catalase and quinones. Under anaerobic cultivation conditions, lactate was produced from d-glucose with the production of formate, acetate and ethanol with a molar ratio of approximately 2 : 1 : 1. Under aerobic cultivation conditions, acetate and lactate were produced from d-glucose. The isolates were slightly halophilic, highly halotolerant and alkaliphilic. The optimum NaCl concentration for growth ranged between 2.0 % and 5.0 % (w/v), with a growth range of 0–1 % to 15–17.5 %. The optimum pH for growth ranged between 8.5 and 9.5, with a growth range of 7.0–7.5 to 9.5–10.0. Comparative sequence analysis of the 16S rRNA genes revealed that the isolates occupied a phylogenetic position within the genus Alkalibacterium , showing the highest sequence similarity (98.2 %) to Alkalibacterium kapii T22-1-2T. The isolates constituted a single genomic species with DNA–DNA hybridization values of 79–100 % among the isolates and <29 % between the isolates and other members of the genus Alkalibacterium , from which the isolates were different in motility and flagellation, growth responses to NaCl concentrations and pH, and profiles of sugar fermentation. The DNA G+C contents were between 36.0 and 37.6 mol%. The cell-wall peptidoglycan was type A4β, Orn-d-Asp. The major components of cellular fatty acids were C14 : 0, C16 : 0 and C16 : 1ω9c. Based on the phenotypic characteristics and genetic distinctness, the isolates are classified as a novel species within the genus Alkalibacterium , for which the name Alkalibacterium gilvum sp. nov. is proposed. The type strain is 3AD-1T ( = DSM 25751T = JCM 18271T).

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Insights from mercury stable isotopes on terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra

Biogeosciences ◽

10.5194/bg-16-4051-2019 ◽

2019 ◽

Vol 16 (20) ◽

pp. 4051-4064 ◽

Cited By ~ 11

Author(s):

Martin Jiskra ◽

Jeroen E. Sonke ◽

Yannick Agnan ◽

Detlev Helmig ◽

Daniel Obrist

Keyword(s):

Stable Isotope ◽

Dominant Role ◽

Arctic Tundra ◽

Atmospheric Mercury ◽

The Arctic ◽

Night Time ◽

Field Station ◽

Terrestrial Atmosphere ◽

Tundra Ecosystem ◽

Flux Measurements

Abstract. The tundra plays a pivotal role in the Arctic mercury (Hg) cycle by storing atmospheric Hg deposition and shuttling it to the Arctic Ocean. A recent study revealed that 70 % of the atmospheric Hg deposition to the tundra occurs through gaseous elemental mercury (GEM or Hg(0)) uptake by vegetation and soils. Processes controlling land–atmosphere exchange of Hg(0) in the Arctic tundra are central, but remain understudied. Here, we combine Hg stable isotope analysis of Hg(0) in the atmosphere, interstitial snow air, and soil pore air, with Hg(0) flux measurements in a tundra ecosystem at Toolik Field Station in northern Alaska (USA). In the dark winter months, planetary boundary layer (PBL) conditions and Hg(0) concentrations were generally stable throughout the day and small Hg(0) net deposition occurred. In spring, halogen-induced atmospheric mercury depletion events (AMDEs) occurred, with the fast re-emission of Hg(0) after AMDEs resulting in net emission fluxes of Hg(0). During the short snow-free growing season in summer, vegetation uptake of atmospheric Hg(0) enhanced atmospheric Hg(0) net deposition to the Arctic tundra. At night, when PBL conditions were stable, ecosystem uptake of atmospheric Hg(0) led to a depletion of atmospheric Hg(0). The night-time decline of atmospheric Hg(0) was concomitant with a depletion of lighter Hg(0) isotopes in the atmospheric Hg pool. The enrichment factor, ε202Hgvegetationuptake=-4.2 ‰ (±1.0 ‰) was consistent with the preferential uptake of light Hg(0) isotopes by vegetation. Hg(0) flux measurements indicated a partial re-emission of Hg(0) during daytime, when solar radiation was strongest. Hg(0) concentrations in soil pore air were depleted relative to atmospheric Hg(0) concentrations, concomitant with an enrichment of lighter Hg(0) isotopes in the soil pore air, ε202Hgsoilair-atmosphere=-1.00 ‰ (±0.25 ‰) and E199Hgsoilair-atmosphere=0.07 ‰ (±0.04 ‰). These first Hg stable isotope measurements of Hg(0) in soil pore air are consistent with the fractionation previously observed during Hg(0) oxidation by natural humic acids, suggesting abiotic oxidation as a cause for observed soil Hg(0) uptake. The combination of Hg stable isotope fingerprints with Hg(0) flux measurements and PBL stability assessment confirmed a dominant role of Hg(0) uptake by vegetation in the terrestrial–atmosphere exchange of Hg(0) in the Arctic tundra.

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Halobaculum magnesiiphilum sp. nov., a magnesium-dependent haloarchaeon isolated from commercial salt

INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY ◽

10.1099/ijs.0.037432-0 ◽

2013 ◽

Vol 63 (Pt_3) ◽

pp. 861-866 ◽

Cited By ~ 15

Author(s):

Hirokazu Shimoshige ◽

Tomoaki Yamada ◽

Hiroaki Minegishi ◽

Akinobu Echigo ◽

Yasuhiro Shimane ◽

...

Keyword(s):

Type Species ◽

Lipid Analysis ◽

Halophilic Archaea ◽

Single Species ◽

16S Rrna Genes ◽

Rrna Genes ◽

Content Type ◽

Link Type ◽

Physiological And Biochemical Characteristics ◽

Low Levels

Two extremely halophilic archaea, strains MGY-184T and MGY-205, were isolated from sea salt produced in Japan and rock salt imported from Bolivia, respectively. Both strains were pleomorphic, non-motile, Gram-negative and required more than 5 % (w/v) NaCl for growth, with optimum at 9–12 %, in the presence of 2 % (w/v) MgCl2 . 6H2O. In the presence of 18 % (w/v) MgCl2 . 6H2O, however, both strains showed growth even at 1.0 % (w/v) NaCl. Both strains possessed two 16S rRNA genes (rrnA and rrnB), and they revealed closest similarity to Halobaculum gomorrense JCM 9908T, the single species with a validly published name of the genus Halobaculum , with similarity of 97.8 %. The rrnA and rrnB genes of both strains were 100 % similar. The rrnA genes were 97.6 % similar to the rrnB genes in both strains. DNA G+C contents of strains MGY-184T and MGY-205 were 67.0 and 67.4 mol%, respectively. Polar lipid analysis revealed that the two strains contained phosphatidylglycerol and phosphatidylglycerol phosphate methyl ester derived from C20C20 archaeol. The DNA–DNA hybridization value between the two strains was 70 % and both strains showed low levels of DNA–DNA relatedness (48–50 %) with Halobaculum gomorrense JCM 9908T. Physiological and biochemical characteristics allowed differentiation of strains MGY-184T and MGY-205 from Halobaculum gomorrense JCM 9908T. Therefore, strains MGY-184T and MGY-205 represent a novel species of the genus Halobaculum , for which the name Halobaculum magnesiiphilum sp. nov. is proposed; the type strain is MGY-184T ( = JCM 17821T = KCTC 4100T).

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