Hymenobacter canadensis sp. nov., isolated from freshwater of the pond in Cambridge Bay, Canada

A Gram-stain-negative, aerobic, reddish-coloured, rod-shaped and non-motile strain PAMC 29467^T, was isolated from freshwater of the pond in Cambridge Bay, Canada. Strain PAMC 29467^T was closely related to Hymenobacter yonginensis (98.1 % 16S rRNA gene similarity). Genomic relatedness analyses showed that strain PAMC 29467^T is distinguishable from H. yonginensis based on average nucleotide identity (91.3 %) and digital DNA-DNA hybridization values (39.3 %). The major fatty acids (>10 %) of strain PAMC 29467^T were summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c), C_15 : 0 iso, C_16 : 1  ω5c and summed feature 4 (C_17 : 1 iso l and/or anteiso B). The major respiratory quinone was menaquinone-7. The genomic DNA G+C content was 61.5 mol%. Strain PAMC 29467^T was separated from the type species in the genus Hymenobacter by its distinct phylogenetic position and some physiological characteristics. As a result, a novel species is proposed, with the name Hymenobacter canadensis sp. nov. (type strain, PAMC 29467^T=KCTC 92787^T=JCM 35843^T).

Description of Hymenobacter sediminicola sp. nov., isolated from contaminated sediment

A polyphasic taxonomic study was conducted on two Gram-negative, non-sporulating, non-motile bacterial strains, S2-20-2^T and S2-21-1, isolated from a contaminated freshwater sediment in China. Comparative 16S rRNA gene sequence studies revealed a clear affiliation of two strains with Bacteroidetes, which showed the highest pairwise sequence similarities with Hymenobacter duratus BT646^T (99.3%), Hymenobacter psychrotolerans Tibet-IIU11^T (99.3%), Hymenobacter kanuolensis T-3^T (97.6%), Hymenobacter swuensis DY53^T (96.9%), Hymenobacter tenuis POB6^T (96.8%), Hymenobacter seoulensis 16F7G^T (96.7%), and Hymenobacter rigui KCTC 12533^T (96.5%). The phylogenetic analysis based on 16S rRNA gene sequences showed that two strains formed a clear phylogenetic lineage with the genus Hymenobacter. Major fatty acids were identified as iso-C_15:0, anteiso-C_15:0, and summed feature 3 (C_16:1 ω6c and/or C_16:1 ω7c/t) and summed feature 4 (iso-C_17:1 I and/or anteiso-C_17:1 B). Major cellular polar lipids were identified as phosphatidylethanolamine, three unidentified aminolipids, an unidentified aminophosopholipid and an unidentified lipid. The respiratory quinone was detected as MK-7 and the genomic DNA G + C content was determined to be 57.9% (genome) for type strain S2-20-2^T and 57.7 mol% (HPLC) for strain S2-21-1. The observed ANI and dDDH values between strain S2-20-2^T and its closely related strains were 75.7-91.4% and 21.2-43.9%, respectively. Based on physiological, biochemical, genetic and genomic characteristics, we propose that strains S2-20-2^T and S2-21-1 represent a novel species of the genus Hymenobacter, for which the name Hymenobacter sediminicola sp. nov. is proposed. The type strain is S2-20-2^T (= CGMCC 1.18734^T = JCM 35801^T).

Culturomics of Bacteria from Radon-Saturated Water of the World's Oldest Radium Mine

Balneotherapeutic water springs, such as those with thermal, saline, sulfur, or any other characteristics, have recently been the subject of phylogenetic studies with a closer focus on the description and/or isolation of phylogenetically novel or biotechnologically interesting microorganisms. Generally, however, most such microorganisms are rarely obtained in pure culture or are even, for now, unculturable under laboratory conditions. In this culture-dependent study of radioactive water springs of Jáchymov (Joachimstahl), Czech Republic, we investigated a combination of classical cultivation approaches with those imitating sampling source conditions. Using these environmentally relevant cultivation approaches, over 1,000 pure cultures were successfully isolated from 4 radioactive springs. Subsequent dereplication yielded 121 unique taxonomic units spanning 44 genera and 9 taxonomic classes, ~10% of which were identified as hitherto undescribed taxa. Genomes of the latter were sequenced and analyzed, with a special focus on endogenous defense systems to withstand oxidative stress and aid in radiotolerance. Due to their origin from radioactive waters, we determined the resistance of the isolates to oxidative stress. Most of the isolates were more resistant to menadione than the model strain Deinococcus radiodurans DSM 20539T. Moreover, isolates of the Deinococcacecae, Micrococcaceae, Bacillaceae, Moraxellaceae, and Pseudomonadaceae families even exhibited higher resistance in the presence of hydrogen peroxide. In summary, our culturomic analysis shows that subsurface water springs contain diverse bacterial populations, including as-yet-undescribed taxa and strains with promising biotechnological potential. Furthermore, this study suggests that environmentally relevant cultivation techniques increase the efficiency of cultivation, thus enhancing the chance of isolating hitherto uncultured microorganisms. IMPORTANCE The mine Svornost in Jáchymov (Joachimstahl), Czech Republic is a former silver-uranium mine and the world's first and for a long time only radium mine, nowadays the deepest mine devoted to the extraction of water which is saturated with radon and has therapeutic benefits given its chemical properties. This healing water, which is approximately 13 thousand years old, is used under medical supervision for the treatment of patients with neurological and rheumatic disorders. Our culturomic approach using low concentrations of growth substrates or the environmental matrix itself (i.e., water filtrate) in culturing media combined with prolonged cultivation time resulted in the isolation of a broad spectrum of microorganisms from 4 radioactive springs of Jáchymov which are phylogenetically novel and/or bear various adaptive or coping mechanisms to thrive under selective pressure and can thus provide a wide spectrum of capabilities potentially exploitable in diverse scientific, biotechnological, or medical disciplines.

Genomic Insights into the Radiation-Resistant Capability of Sphingomonas qomolangmaensis S5-59T and Sphingomonas glaciei S8-45T, Two Novel Bacteria from the North Slope of Mount Everest

Mount Everest provides natural advantages to finding radiation-resistant extremophiles that are functionally mechanistic and possess commercial significance. (1) Background: Two bacterial strains, designated S5-59T and S8-45T, were isolated from moraine samples collected from the north slope of Mount Everest at altitudes of 5700m and 5100m above sea level. (2) Methods: The present study investigated the polyphasic features and genomic characteristics of S5-59^T and S8-45^T. (3) Results: The major fatty acids and the predominant respiratory menaquinone of S5-59^T and S8-45^T were summed as feature 3 (comprising C16:1 ω6c and/or C16:1 ω7c) and ubiquinone-10 (Q-10). Phylogenetic analyses based on 16S rRNA sequences and average nucleotide identity values among these two strains and their reference type strains were below the species demarcation thresholds of 98.65% and 95%. Strains S5-59^T and S8-45^T harbored great radiation resistance. The genomic analyses showed that DNA damage repair genes, such as mutL, mutS, radA, radC, recF, recN, etc., were present in the S5-59^T and S8-45^T strains. Additionally, strain S5-59^T possessed more genes related to DNA protection proteins. The pan-genome analysis and horizontal gene transfers revealed that strains of Sphingomonas had a consistently homologous genetic evolutionary radiation resistance. Moreover, enzymatic antioxidative proteins also served critical roles in converting ROS into harmless molecules that resulted in resistance to radiation. Further, pigments and carotenoids such as zeaxanthin and alkylresorcinols of the non-enzymatic antioxidative system were also predicted to protect them from radiation. (4) Conclusions: Type strains S5-59^T (=JCM 35564T =GDMCC 1.3193T) and S8-45^T (=JCM 34749T =GDMCC 1.2715T) represent two novel species of the genus Sphingomonas with the proposed name Sphingomonas qomolangmaensis sp. nov. and Sphingomonas glaciei sp. nov. The type strains, S5-59^T and S8-45^T, were assessed in a deeply genomic study of their radiation-resistant mechanisms and this thus resulted in a further understanding of their greater potential application for the development of anti-radiation protective drugs.

Soil substrate culturing approaches recover diverse members of Actinomycetota from desert soils of Herring Island, East Antarctica

Antimicrobial resistance is an escalating health crisis requiring urgent action. Most antimicrobials are natural products (NPs) sourced from Actinomycetota, particularly the Streptomyces. Underexplored and extreme environments are predicted to harbour novel microorganisms with the capacity to synthesise unique metabolites. Herring Island is a barren and rocky cold desert in East Antarctica, remote from anthropogenic impact. We aimed to recover rare and cold-adapted NP-producing bacteria, by employing two culturing methods which mimic the natural environment: direct soil culturing and the soil substrate membrane system. First, we analysed 16S rRNA gene amplicon sequencing data from 18 Herring Island soils and selected the soil sample with the highest Actinomycetota relative abundance (78%) for culturing experiments. We isolated 166 strains across three phyla, including novel and rare strains, with 94% of strains belonging to the Actinomycetota. These strains encompassed thirty-five ‘species’ groups, 18 of which were composed of Streptomyces strains. We screened representative strains for genes which encode polyketide synthases and non-ribosomal peptide synthetases, indicating that 69% have the capacity to synthesise polyketide and non-ribosomal peptide NPs. Fourteen Streptomyces strains displayed antimicrobial activity against selected bacterial and yeast pathogens using an in situ assay. Our results confirm that the cold-adapted bacteria of the harsh East Antarctic deserts are worthy targets in the search for bioactive compounds.

Contrasting elevational patterns and underlying drivers of stream bacteria and fungi at the regional scale on the Tibetan Plateau

Elevational gradients are the focus of development and evaluation of general theories on biodiversity. However, elevational studies of microorganisms and the underlying mechanisms remain understudied, especially at regional scales. Here, we examined stream bacterial and fungal communities along an elevational gradient of 990-4,600 m with a geographic distance up to 500 km in the southeastern Tibetan Plateau and further analyzed their elevational patterns and drivers of three biodiversity indicators, including species richness, ecological uniqueness and community composition. Bacteria and fungi showed distinct elevational trends in species richness and consistently decreasing patterns in their ecological uniqueness. The distance-decay relationships were concordant for the two microbial groups, while fungi showed higher dissimilarity and a lower turnover rate. Interestingly, bacterial and fungal compositions substantially differed between the elevations below and above 3,000 m. Climate predictors, such as the mean annual temperature and precipitation seasonality, had greater effects than local environment drivers. Notably, fungal diversity was mainly influenced by climate, while bacterial diversity was explained by the shared contributions of climate and local factors. Collectively, these findings revealed the elevational patterns of stream microbial biodiversity across mountains on a large spatial scale and highlight their underlying response mechanisms to environmental predictors.

Hymenobacter siberiensis sp. nov., isolated from a marine sediment of the East Siberian Sea and Hymenobacter psoromatis sp. nov., isolated from an Antarctic lichen

Gram-stain-negative, strictly aerobic, red-pink-coloured, rod-shaped and non-motile bacterial strains PAMC 29290, PAMC 29294T and PAMC 29296 were isolated from marine surface sediment sampled in the East Siberian Sea and strains PAMC 26553 and PAMC 26554T were obtained from an Antarctic lichen. Strains PAMC 29290, PAMC 29294T and PAMC 29296 were closely related to Hymenobacter artigasi (98.8 % 16S rRNA gene similarity), Hymenobacter antarcticus (97.3 %) and Hymenobacter glaciei (96.9 %), and PAMC 26553 and PAMC 26554T showed high similarity to Hymenobacter ginsengisoli (97.0 %), Hymenobacter rivuli (96.1 %) and Hymenobacter setariae (95.9 %). Genomic relatedness analyses showed that strains PAMC 29290, PAMC 29294T and PAMC 29296 could be distinguished from H. artigasi by average nucleotide identity (ANI; 93.1–93.2 %) and digital DNA–DNA hybridization (dDDH; 50.3–51.0 %) values. Strains PAMC 26553 and PAMC 26554T could be clearly distinguished from H. ginsengisoli with ANI values <79.8 % and dDDH values <23.3 %. The major fatty acids of strains PAMC 29290, PAMC 29294T and PAMC 29296 were C15 : 0 iso (21.0–26.0 %), summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c; 17.4–18.2 %), C15 : 0 anteiso (12.7–19.1 %) and summed feature 4 (C17 : 1 iso I and/or anteiso B; 8.6–16.1 %) and those of strains PAMC 26553 and PAMC 26554T were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c; 20.7–22.2 %), C15 : 0 anteiso (17.5–19.7 %) and summed feature 4 (C17 : 1 iso I and/or anteiso B; 15.5–18.1 %). The major respiratory quinone was MK-7. The genomic DNA G+C contents were 60.6–60.8 mol%. The polar lipids of PAMC 29294T were found to consist of phosphatidylethanolamine, four unidentified aminolipids, an unidentified aminophospholipid and five unidentified lipids; those of PAMC 26554T were phosphatidylethanolamine, three unidentified aminolipids, four unidentified aminophospholipid and two unidentified lipids. The distinct phylogenetic position and some physiological characteristics distinguished the novel strains from closely related type strains in the genus Hymenobacter . Thus, two novel species are proposed, with the names Hymenobacter siberiensis sp. nov. (type strain, PAMC 29294T=KCTC 82466T=JCM 34574T) and Hymenobacter psoromatis sp. nov. (type strain, PAMC 26554T=KCTC 82464T=JCM 34572T), respectively.

Ice Melt-Induced Variations of Structural and Functional Traits of the Aquatic Microbial Community along an Arctic River (Pasvik River, Norway)

The effects of climate change-induced ice melting on the microbial communities in different glacial-fed aquatic systems have been reported, but seasonal dynamics remain poorly investigated. In this study, the structural and functional traits of the aquatic microbial community were assessed along with the hydrological and biogeochemical variation patterns of the Arctic Pasvik River under riverine and brackish conditions at the beginning (May = Ice-melt (−)) and during the ice-melting season (July = Ice-melt (+)). The microbial abundance and morphometric analysis showed a spatial diversification between the riverine and brackish stations. Results highlighted different levels of microbial respiration and activities with different carbon and phosphorous utilization pathways, thus suggesting an active biogeochemical cycling along the river especially at the beginning of the ice-melting period. At Ice-melt (−), Gammaproteobacteria and Alphaproteobacteria were dominant in riverine and brackish stations, respectively. Conversely, at Ice-melt (+), the microbial community composition was more homogeneously distributed along the river (Gammaproteobacteria > Alphaproteobacteria > Bacteroidetes). Our findings provide evidence on how riverine microbial communities adapt and respond to seasonal ice melting in glacial-fed aquatic ecosystems.

Hymenobacter guriensis sp. nov., and Hymenobacter duratus sp. nov., Radiation-Resistant Species Isolated from Soil in South Korea

Two novel Gram-stain-negative, non-motile, aerobic, rod-shaped, circular, convex, red-colored and UV-tolerant strains BT594^T and BT646^T were isolated from soil collected in Guri city (37° 36' 0″ N, 127° 9' 0″ E) and Gwangju city (37° 22' 0″ N, 127° 17' 0″ E), respectively, South Korea. 16S rDNA sequence analysis indicated that strains BT594^T and BT646^T belong to a distinct lineage within the genus Hymenobacter (family Hymenobacteraceae, order Cytophagales, class Cytophagia, phylum Bacteroidetes, kingdom Bacteria). The 16S rDNA gene sequence similarity between the two strains BT594^T and BT646^T was 96.2%. The strain BT594^T was closely related to Hymenobacter psychrotolerans Tibet-IIU11^T (97.0% 16S rDNA gene similarity) and Hymenobacter tibetensis XTM003^T (96.3%). The strain BT646^T was closely related to Hymenobacter psychrotolerans Tibet-IIU11^T (98.6%), Hymenobacter kanuolensis T-3 ^T (96.8%) and Hymenobacter perfusus LMG 26000 ^T (96.7%). The two strains were found to have the same quinone system, with MK-7 as the major respiratory quinone. The major polar lipids of strains BT594^T and BT646^T were phosphatidylethanolamine (PE) and aminophospholipids (APL). The major cellular fatty acids of strain BT594^T were anteiso-C_15:0 (17.9%), iso-C_15:0 (16.1%) and summed feature 3 (C_16:1 ω6c / C_16:1 ω7c) (10.0%). The major cellular fatty acids of strain BT646^T were summed feature 3 (C_16:1 ω6c / C_16:1 ω7c) (18.3%), C_16:0 (17.2%) and summed feature 4 (iso-C_17:1 I / anteiso-C_17:1 B) (14.5%). Based on the polyphasic analysis, strains BT594^T and BT646^T can be suggested as two novel bacterial species within the genus Hymenobacter and the proposed names are Hymenobacter guriensis and Hymenobacter duratus, respectively. The type strain of Hymenobacter guriensis is BT594^T (= KCTC 21863 ^T = NBRC 114853 ^T) and the type strain of Hymenobacter duratus is BT646^T (= KCTC 21915 ^T = NBRC 114854 ^T).

Hymenobacter terrestris sp. nov. and Hymenobacter lapidiphilus sp. nov., isolated from regoliths in Antarctica

A group of four psychrotrophic bacterial strains was isolated on James Ross Island (Antarctica) in 2013. All isolates, originating from different soil samples, were collected from the ice-free northern part of the island. They were rod-shaped, Gram-stain-negative, and produced moderately slimy red-pink pigmented colonies on R2A agar. A polyphasic taxonomic approach based on 16S rRNA gene sequencing, whole-genome sequencing, MALDI-TOF MS, rep-PCR analyses, chemotaxonomic methods and extensive biotyping was used to clarify the taxonomic position of these isolates. Phylogenetic analysis based on 16S rRNA gene sequences showed that the isolates belonged to the genus Hymenobacter. The closest relative was Hymenobacter humicola CCM 8763^T, exhibiting 98.3 and 98.9% 16S rRNA pairwise similarity with the reference isolates P5342^T and P5252^T, respectively. Average nucleotide identity, digital DNA-DNA hybridization and core gene distances calculated from the whole-genome sequencing data confirmed that P5252^T and P5342^T represent two distinct Hymenobacter species. The menaquinone systems of both strains contained MK-7 as the major respiratory quinone. The predominant polar lipids for both strains were phosphatidylethanolamine and one unidentified glycolipid. The major components in the cellular fatty acid composition were summed feature 3 (C_16:1 ω7c/C_16:1ω6c), C_16:1ω5c, summed feature 4 (anteiso-C_17:1 B/iso-C_17:1 I), anteiso-C_15:0 and iso-C_{15 : 0} for all isolates. Based on the obtained results, two novel species are proposed, for which the names Hymenobacter terrestris sp. nov. (type strain P5252^T=CCM 8765^T=LMG 31495^T) and Hymenobacter lapidiphilus sp. nov. (type strain P5342^T=CCM 8764^T=LMG 30613^T) are suggested.

Spirosoma aureum sp. nov., and Hymenobacter russus sp. nov., radiation-resistant bacteria in Cytophagales order isolated from soil

A Gram-stain-negative, aerobic, nonmotile, yellow-colored strain BT328^T and Gram-stain-negative, aerobic, non-motile, red-colored strain BT18^T were isolated from the soil collected in Korea. Phylogenetic analyses based on 16S rRNA gene sequence revealed that strain BT328^T formed a distinct lineage within the family Spirosomaceae (order Cytophagales, class Cytophagia) and was most closely related to a member of the genus Spirosoma, Spirosoma terrae 15J9-4^T (95.9% 16S rRNA gene sequence similarity). Optimal growth occurred at 25 °C, pH 7.0 and in the absence of NaCl. The predominant cellular fatty acids were summed feature 3 (C_16:1 ω6c/C_16:1 ω7c) and C_16:1 ω5c. The major respiratory quinone was MK-7. The major polar lipid was phosphatidylethanolamine. Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain BT18^T formed a distinct lineage within the family Hymenobacteraceae (order Cytophagales, class Cytophagia, phylum Bacteroidetes) and was most closely related to members of the genus Hymenobacter, Hymenobacter knuensis 16F7C-2^T (97.0% 16S rRNA gene sequence similarity). Optimal growth occurred at 25 °C and pH 7.0 without NaCl. The major fatty acids were iso-C_15:0 and anteiso-C_15:0. The major menaquinone was MK-7. The major polar lipid was phosphatidylethanolamine. Biochemical, chemotaxonomic and phylogenetic analyses indicated that strains BT328^T and BT18^T represents a novel bacterial species within the genus Spirosoma and Hymenobacter, respectively. For which the name Spirosoma aureum and Hymenobacter russus is proposed. The type strain of S. aureum is BT328^T (=KCTC 72365^T = NBRC 114506^T) and the type strain of H. russus is BT18^T (=KCTC 62610^T = NBRC 114380^T).

Hymenobacter baengnokdamensis sp. nov., Isolated from the Soil of a Crater Lake in Korea

An aerobic, Gram-stain-negative, non-motile, non-spore-forming, rod-shaped and pink-colored bacterial strain, designated BRD72^T, was isolated from a crater lake (Baengnokdam) at the top of Mt. Hallasan in the Republic of Korea. Cells were catalase-positive and oxidase-negative. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the isolate was a member of the genus Hymenobacter and most closely related to Hymenobacter marinus KJ035^T (96.2% similarity). The isolate was found to produce carotenoid pigment, but not flexirubin-type pigment. The predominant fatty acids of strain BRD72^T were summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c, 21.6%), iso-C_15:0 (17.9%), anteiso-C_15:0 (13.3%) and summed feature 4 (iso-C_17:1 I and/or anteiso-C_17:1 B, 11.3%). The major polar lipids were phosphatidylethanolamine, an unidentified amino lipid, and two unidentified aminophospholipids. The main respiratory quinone was menaquinone-7 (MK-7), and the main polyamine was homospermidine. The DNA G+C content was 59.8 mol%. Based on the phylogenetic, physiological, and chemotaxonomic characteristics, strain BRD72^T represents a novel species, for which the name Hymenobacter baengnokdamensis sp. nov. is proposed. The type strain is BRD72^T (= KCTC 72649^T = JCM 33837^T).

Hymenobacter artigasi sp. nov., isolated from air sampling in maritime Antarctica

A rod-shaped and Gram-stain-negative bacterial strain, 1B^T, was isolated from an air sample collected at King George Island, maritime Antarctica. Strain 1B^T is strictly aerobic, psychrophilic, catalase-positive, oxidase-positive and non-motile. Growth of strain 1B^T is observed at 0-20 °C (optimum, 10 °C), pH 6.0-8.0 (optimum, pH 8.0) and in the presence of 0-1.0% NaCl (optimum, 0.5 % NaCl). Phylogenetic analysis based on 16S rRNA gene sequences places strain 1B^T within the genus Hymenobacter and shows the highest similarity to Hymenobacter antarcticus VUG-A42aa^T (97.5 %). The predominant menaquinone of strain 1B^T is MK-7 and the major fatty acids (>10 %) comprise summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c; 32.5 %), iso-C_15 : 0 (17.6 %) and anteiso C_15 : 0 (12.3 %). The polar lipid profile consists of the major compounds phosphatidylethanolamine, phosphatidylserine, two unidentified aminolipids and one unidentified phospholipid. The DNA G+C content based on the draft genome sequence is 61.2 mol%. Based on the data from the current polyphasic study, 1B^T represents a novel species of the genus Hymenobacter, for which the name Hymenobacter artigasi sp. nov. is suggested. The type strain is 1B^T (=CCM 8970^T=CGMCC 1.16843^T).

Hymenobacter humicola sp. nov., isolated from soils in Antarctica

A set of three psychrotrophic bacterial strains was isolated from different soil samples collected at the deglaciated northern part of James Ross Island (Antarctica) in 2014. All isolates were rod-shaped, Gram-stain-negative, non-motile, catalase-positive and oxidase-negative, and produced moderately slimy red-pink pigmented colonies on Reasoner's 2A (R2A) agar. A polyphasic taxonomic approach based on 16S rRNA gene sequencing, whole-genome sequencing, automated ribotyping, MALDI-TOF MS, chemotaxonomy methods and extensive biotyping using conventional tests and commercial identification kits was applied to the isolates in order to clarify their taxonomic position. Phylogenetic analysis based on the 16S rRNA gene showed that all isolates belonged to the genus Hymenobacter with the closest relative being Hymenobacter aerophilus DSM 13606^T, exhibiting 98.5 % 16S rRNA gene pairwise similarity to the reference isolate P6312^T. Average nucleotide identity values calculated from the whole-genome sequencing data proved that P6312^T represents a distinct Hymenobacter species. The major components of the cellular fatty acid composition were summed feature 3 (C_16 : 1 ω7c/C_16 : 1 ω6c), C_16 : 1 ω5c, summed feature 4 (C_17 : 1 anteiso B/iso I), C_15 : 0 anteiso and C_15 : 0 iso. The menaquinone system of strain P6312^T contained MK-7 as the major respiratory quinone. The predominant polar lipids were phosphatidylethanolamine and an unidentified phospholipid. Moderate to minor amounts of three unidentified polar lipids, four unidentified aminophospholipids, one unidentified glycolipid and one unidentified phospholipid were also present. Based on the obtained results, we propose a novel species for which the name Hymenobacterhumicola sp. nov. is suggested, with the type strain P6312^T (=CCM 8763^T=LMG 30612^T).

Hymenobacter profundi sp. nov., isolated from deep-sea water

A Gram-stain-negative, rod-shaped, red-pigmented, aerobic bacterium, strain M2^T, was isolated from a seawater sample collected from the western Pacific Ocean at a depth of 1000 m and characterized using polyphasic taxonomy. Strain M2^T was catalase-positive and oxidase-negative. Cells grew at 4-33 °C (optimum, 25 °C), at pH 6-9 (optimum, 7) and with 0-4 % (w/v) (optimum, 1 %) NaCl. Phylogenetic trees based on 16S rRNA gene sequences showed that strain M2^T was associated with the genus Hymenobacter. Strain M2^T showed the highest 16S rRNA gene sequence similarities to Hymenobacter actinosclerus CCUG 39621^T (95.7 %), Hymenobacter tibetensis XTM003^T (95.6 %) and Hymenobacter psychrotolerans Tibet-IIU11^T (95.2 %). The DNA G+C content was 59.98 mol%. Strain M2^T contained C_16 : 1ω5c (25.0 %), iso-C_15 : 0 (23.9 %) and summed feature 3 (C_16 : 1ω6c and/or C_16 : 1ω7c, 20.4 %) as major cellular fatty acids. The major quinone of strain M2^T was menaquinone 7 and the major polar lipid was phosphatidylethanolamine. The major polyamine of strain M2^T was sym-homospermidine. The phylogenetic analysis and physiological and biochemical data showed that strain M2^T should be classified as representing a novel species of the genus Hymenobacter, for which the name Hymenobacter profundi sp. nov. is proposed. The type strain is M2^T (=CCTCC AB 2017185^T=KCTC 62120^T).

Hymenobacter defluvii sp. nov., isolated from wastewater of an acidic water neutralization facility

A non-motile, pink-coloured and rod-shaped bacterium, designated strain POA9^T, was isolated from a wastewater treatment facility, Republic of Korea. Cells were Gram-reaction-negative, aerobic, catalase-positive and oxidase-negative. The major fatty acids were C16 : 1ω5c, iso-C15 : 0, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and anteiso-C15 : 0. The strain contained MK-7 as the only isoprenoid quinone, phosphatidylethanolamine as the major polar lipid and sym-homospermidine as the major polyamine. The DNA G+C content was 57 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain POA9^T forms a distinct evolutionary lineage within the radiation enclosing the members of the genus Hymenobacter, sharing the highest similarity with Hymenobacter actinosclerus CCUG 39621^T (95.5 % sequence similarity) followed by Hymenobacterseoulensis 16F7G^T (95.5 %), Hymenobactertibetensis XTM003^T (95.4 %), Hymenobacterrutilus K2-33028^T (95.4 %) and Hymenobacter psychrotolerans Tibet-IIU11^T (94.9 %). A number of phenotypic characteristics distinguished strain POA9^T from the related members of the genus Hymenobacter. On the basis of the evidence presented in this study, a novel species, Hymenobacter defluvii sp. nov., is proposed for strain POA9^T (=KCTC 52270^T=JCM 31658^T).

Microbial biodiversity assessment of the European Space Agency's ExoMars 2016 mission

BACKGROUND

The ExoMars 2016 mission, consisting of the Trace Gas Orbiter and the Schiaparelli lander, was launched on March 14 2016 from Baikonur, Kazakhstan and reached its destination in October 2016. The Schiaparelli lander was subject to strict requirements for microbial cleanliness according to the obligatory planetary protection policy. To reach the required cleanliness, the ExoMars 2016 flight hardware was assembled in a newly built, biocontrolled cleanroom complex at Thales Alenia Space in Turin, Italy. In this study, we performed microbiological surveys of the cleanroom facilities and the spacecraft hardware before and during the assembly, integration and testing (AIT) activities.

METHODS

Besides the European Space Agency (ESA) standard bioburden assay, that served as a proxy for the microbiological contamination in general, we performed various alternative cultivation assays and utilised molecular techniques, including quantitative PCR and next generation sequencing, to assess the absolute and relative abundance and broadest diversity of microorganisms and their signatures in the cleanroom and on the spacecraft hardware.

RESULTS

Our results show that the bioburden, detected microbial contamination and microbial diversity decreased continuously after the cleanroom was decontaminated with more effective cleaning agents and during the ongoing AIT. The studied cleanrooms and change room were occupied by very distinct microbial communities: Overall, the change room harboured a higher number and diversity of microorganisms, including Propionibacterium, which was found to be significantly increased in the change room. In particular, the so called alternative cultivation assays proved important in detecting a broader cultivable diversity than covered by the standard bioburden assay and thus completed the picture on the cleanroom microbiota.

CONCLUSION

During the whole project, the bioburden stayed at acceptable level and did not raise any concern for the ExoMars 2016 mission. The cleanroom complex at Thales Alenia Space in Turin is an excellent example of how efficient microbiological control is performed.

Hymenobacter tenuis sp. nov., isolated from wastewater of an acidic water neutralization facility

A non-motile, red-pink-coloured, rod-shaped bacterium, designated strain POB6T, was isolated from a wastewater treatment facility, Republic of Korea. Cells were Gram-stain-negative, aerobic, catalase-positive and oxidase-negative. The major fatty acids were iso-C15 : 0, C16 : 1ω5c, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c) and summed feature 4 (iso-C17 : 1 I and/or anteiso-C17 : 1 B). The strain contained menaquinone MK-7 as the only isoprenoid quinone, phosphatidylethanolamine as the major polar lipid and sym-homospermidine as the major polyamine. The DNA G+C content was 61 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain POB6T forms a distinct evolutionary lineage within the radiation enclosing the members of the genus Hymenobacter, sharing the highest similarity with Hymenobacterrigui WPCP131T (97.5 %) followed by Hymenobacter xinjiangensis X2-1gT (97.2 %), Hymenobacter perfusus A1-12T (97.2 %) and Hymenobacter gelipurpurascens Txg-1T (97.1 %). A number of phenotypic characteristics distinguished strain POB6T from related members of the genus Hymenobacter. On the basis of the evidence presented in this study, a novel species, Hymenobacter tenuis sp. nov., is proposed, with POB6T (=KCTC 52271T=JCM 31659T) as the type strain.

Hymenobacter daeguensis sp. nov. isolated from river water

A Gram-stain-negative, non-motile, non-spore-forming, rod-shaped, aerobic bacterial strain, designated 16F3Y-2^T, was isolated from the Han River, South Korea, and was characterized taxonomically using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain 16F3Y-2^T belonged to the family Cytophagaceae in the phylum Bacteroidetes and was most closely related to 'Hymenobacter terrae' DG7A (98.01%), H. soli PB17^T (97.26%), H. glaciei VUG-A130^T (96.78%), H. antarcticus VUG-A42aa^T (96.72%), H. ruber PB156^T (96.61%), and H. saemangeumensis GSR0100^T (95.77%). The G+C content of the genomic DNA of strain 16F3Y-2^T was 62.9 mol%. The isolate contained MK-7 as the predominant respiratory quinone, and summed feature 3 (C_16:1 ω7c/C_16:1 ω6c; 35.5%), C_15:0 iso (16.9%), C_16:1 ω5c (10.9%), and C_15:0 anteiso (9.9%) as major fatty acids. The major polar lipid was phosphatidylethanolamine. Phenotypic and chemotaxonomic data supported the affiliation of strain 16F3Y-2^T with the genus Hymenobacter. However, strain 16F3Y-2^T exhibited relatively low levels of DNA-DNA relatedness with 'H. terrae' KCTC 32554 (44.1%) and H. soli KCTC 12607^T (24.3%), clearly indicating that the isolate constitutes a new genospecies. Strain 16F3Y-2^T could be differentiated from its phylogenetic neighbors on the basis of several phenotypic, genotypic, and chemotaxonomic features. Therefore, strain 16F3Y-2^T represents a novel species in the genus Hymenobacter, for which the name Hymenobacter daeguensis sp. nov. is proposed. The type strain is 16F3Y-2^T (=KCTC 52537^T =JCM 31654^T).

A highly diverse, desert-like microbial biocenosis on solar panels in a Mediterranean city

Microorganisms colonize a wide range of natural and artificial environments although there are hardly any data on the microbial ecology of one the most widespread man-made extreme structures: solar panels. Here we show that solar panels in a Mediterranean city (Valencia, Spain) harbor a highly diverse microbial community with more than 500 different species per panel, most of which belong to drought-, heat- and radiation-adapted bacterial genera, and sun-irradiation adapted epiphytic fungi. The taxonomic and functional profiles of this microbial community and the characterization of selected culturable bacteria reveal the existence of a diverse mesophilic microbial community on the panels’ surface. This biocenosis proved to be more similar to the ones inhabiting deserts than to any human or urban microbial ecosystem. This unique microbial community shows different day/night proteomic profiles; it is dominated by reddish pigment- and sphingolipid-producers, and is adapted to withstand circadian cycles of high temperatures, desiccation and solar radiation.

Hymenobacter wooponensis sp. nov., isolated from wetland freshwater

A non-motile and rod-shaped bacterium, designated strain WM78T, was isolated from freshwater collected from the Woopo wetland (Republic of Korea). Cells were Gram-stain-negative, aerobic, catalase-positive and oxidase-negative. The major fatty acids were iso-C15:0, anteiso-C15:0, C16:1ω7c and/or C16:1ω6c and iso-C17:1 I and/or anteiso-C17:1 B. The strain contained MK-7 as the major isoprenoid quinone, phosphatidylethanolamine as the major polar lipid and sym-homospermidine as the major polyamine. The genomic DNA G+C content was 62 mol%. A phylogenetic tree based on 16S rRNA gene sequences showed that strain WM78T forms evolutionary lineage within the radiation comprising members of the genus Hymenobacter with Hymenobacter gelipurpurascens Txg1T (97.7 % sequence similarity) as its nearest neighbour. A number of phenotypic characteristics distinguished strain WM78T from related members of the genus Hymenobacter. The evidence presented in this study support the designation of strain WM78T as a representative of a novel species in the genus Hymenobacter for which the name Hymenbactor wooponensis sp. nov. is proposed. The type strain is WM78T ( = KCTC 32528T = JCM 19491T).

Hymenobacter arcticus sp. nov., isolated from glacial till

A novel, red–pink-pigmented strain, designated R2-4T, was isolated from a till sample near Ny-Alesund, Svalbard Archipelago, Norway. Cells were aerobic, Gram-stain-negative and rod-shaped. Growth occurred at 4–30 °C (optimum, 20–22 °C), at pH 6.0–9.0 (optimum, pH 7.0) and with 0–1 % NaCl added to R2A agar. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain R2-4T belonged to the genus Hymenobacter . 16S rRNA gene sequence similarity between strain R2-4T and the type strains of related species of the genus ranged from 94.51 to 96.05 %. Strain R2-4T contained iso-C15 : 0, anteiso-C15 : 0, summed feature 3 (C16 : 1ω6c and/or C16 : 1ω7c), summed feature 4 (C17 : 1 anteiso B and/or iso I) and C16 : 1ω5c as the major cellular fatty acids, MK-7 as the major respiratory quinone, and phosphatidylethanolamine, unknown aminophospholipids, unknown aminolipids and unknown lipids as the main polar lipids. The polyamine was sym-homospermidine. The DNA G+C content of strain R2-4T was 61.6 mol%. On the basis of phylogenetic, physiological and chemotaxonomic data, strain R2-4T is considered to represent a novel species of the genus Hymenobacter , for which the name Hymenobacter arcticus sp. nov. is proposed. The type strain is R2-4T ( = CCTCC AB 2012104T = KACC 16881T).

Hymenobacter qilianensis sp. nov., isolated from a subsurface sandstone sediment in the permafrost region of Qilian Mountains, China and emended description of the genus Hymenobacter

A red-pink, Gram-negative, rod-shaped, non-motile, non-spore-forming bacterium, designated strain DK6-37 was isolated from the permafrost region of Qilian Mountains in northwest of China. Phylogenetic analysis based on 16S rRNA gene sequencing indicated that this isolate represents a novel member of the genus Hymenobacter, with low sequence similarities (<97 %) to recognized Hymenobacter species. Optimum growth was observed at 28 °C, pH 7.0 and 0 % NaCl. The strain was found to contain MK-7 as the predominant menaquinone. The polar lipids were identified as phosphatidylethanolanmine, two unknown aminophospholipids, one unknown aminolipid and three unknown polar lipids. The major fatty acids were identified as summed feature 3 (C16:1 ω7c/C16:1 ω6c as defined by MIDI), summed feature 4 (anteiso-C17:1 B/iso-C17:1 I), C16:1 ω5c, iso-C17:0 3-OH, iso-C15:0 and C18:0. The DNA G + C content was determined to be 67.4 mol %. On the basis of the polyphasic evidence presented, it is proposed that strain DK6-37 represents a novel species of the genus Hymenobacter, for which the name Hymenobacter qilianensis sp. nov. is proposed. The type strain is DK6-37(T) (= CGMCC 1.12720(T) = JCM 19763(T)).

Hymenobacter kanuolensis sp. nov., a novel radiation-resistant bacterium

A Gram-reaction-negative, rod-shaped, non-motile, red-pigmented, radiation-resistant, aerobic bacterium designated T-3(T) was isolated from a soil sample from the Qinghai-Tibet Plateau in Tibet, China, after exposure to 10 kGy gamma radiation. Phylogenetic analysis based on 16S rRNA sequences indicated that this isolate represented a novel member of the genus Hymenobacter. Sequence identities of the 16S rRNA gene of strain T-3(T) with the type strains of species of the genus Hymenobacter with validly published names range from 89% to 97%, and the most closely related species is Hymenobacter psychrotolerans Tibet-IIU11(T) (97%). The DNA-DNA relatedness between strain T-3(T) and H. psychrotolerans is 59.10%. The major fatty acids of strain T-3(T) were iso-C(15 : 0) (27.66%), summed feature 4 (iso-C(17 : 1)I and/or anteiso-C(17 : 1)B, 15.84%), anteiso-C(15 : 0) (14.08%) and summed feature 3 (C(16 : 1)ω7c and/or C(16 : 1)ω6c, 12.38%). The major menaquinone of strain T-3(T) was MK-7. Phosphatidylethanolamine (PE) was predominant in the polar lipid profile. The G+C content of the DNA of strain T-3(T) was 69.17 mol%. On the basis of the results of the polyphasic characterization presented in this study, it is concluded that strain T-3(T) represents a novel species of the genus Hymenobacter, for which the name Hymenobacter kanuolensis is proposed. The type strain is T-3(T) ( = ACCC 05760(T) = KCTC 32407(T)).

Description of Hymenobacter arizonensis sp. nov. from the southwestern arid lands of the United States of America

Strain OR362-8(T) was isolated from a biological soil crust sample collected from the southwestern arid lands of the United States of America, using BG11-PGY medium. Cells of OR362-8(T) were found to be rod shaped; occur singly, as pairs and in groups; non-motile; positive for catalase, oxidase, phosphatase and gelatinase; hydrolyze starch; contain iso-C(15:0), anteiso-C(15:0), iso-C(15:1)G, C(16:1ω5c) and summed feature 3 (C(16:1(ω7c))/iso-C(15:0) 2OH as defined by the MIDI system) as the major fatty acids; and MK-7 as the sole respiratory quinone. A BLAST sequence similarity search using 16S rRNA gene sequence of OR362-8(T) identified Hymenobacter as the nearest genus with a similarity of 90.4-96.9 %. The phylogenetic analyses based on the phenetic methods UPGMA, NJ, ME and DNA parsimony resulted in the clustering of OR362-8(T) with Clade 1 Hymenobacter species represented by Hymenobacter glaciei, Hymenobacter antarcticus, Hymenobacter flocculans, Hymenobacter metalli and Hymenobacter soli with the closest being the Hymenobacter glaciei (96.9 % 16S rRNA gene sequence similarity). Besides the strong phylogentic affiliation, OR362-8(T) also exhibited significant phenotypic and chemotaxonomic differences with the members of Clade 1 Hymenobacter spp. More importantly, the DNA G+C content (mol%) of OR362-8(T) is very high (70 %) compared to the nearest species identified by phylogenetic analysis. Based on the phylogenetic, phenotypic and chemotaxonomic characteristics, OR362-8(T) was assigned to a novel species for which we propose here the name Hymenobacter arizonensis sp. nov., with OR362-8(T) (=ATCC BAA 1266(T) = DSM 17860(T) = JCM 13504(T)) as the type strain.

Hymenobacter ginsengisoli sp. nov., isolated from soil of a ginseng field

A Gram-stain-negative, non-motile, red bacterium, designated DCY57(T), was isolated from soil of a ginseng field in a mountainous region of Chungnam province in South Korea. Strain DCY57(T) grew with 0-1 % (w/v) NaCl and the optimum temperature for growth was 30 °C. Strain DCY57(T) contained MK-7 as the predominant menaquinone. The polyamine was sym-homospermidine. The major fatty acids were C(16:1)ω5c, iso-C(15:0), anteiso-C(15:0) and summed feature 3 (containing C(16:1)ω7c and/or C(16:1)ω6c). The major polar lipids were phosphatidylethanolamine, unknown aminophospholipids, unknown aminolipids and unknown lipids. The DNA G+C content was 58.9 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain DCY57(T) was most closely related to members of the genus Hymenobacter. The isolate exhibited 91.7 % 16S rRNA gene sequence similarity with H. soli PB17(T), 94.5 % with H. flocculans A2-50A(T) and 95.8 % with H. metalli A2-91(T). On the basis of the evidence presented in this study, strain DCY57(T) represents a novel species within the genus Hymenobacter, for which the name Hymenobacter ginsengisoli sp. nov. is proposed. The type strain is DCY57(T) ( = KCTC 23674(T) = JCM 17841(T)).

Hymenobacter yonginensis sp. nov., isolated from a mesotrophic artificial lake

A non-motile, red-pigmented bacterium, designated strain HMD1010T, was isolated from an artificial lake located within the campus of Hankuk University of Foreign Studies, Yongin, Korea. A phylogenetic tree based on 16S rRNA gene sequences showed that strain HMD1010T formed a lineage within the genus Hymenobacter and was closely related to the type strains of Hymenobacter rigui (96.7 % sequence similarity) and H. gelipurpurascens (95.6 %). The major fatty acids were C16 : 1ω5c (21.9 %), summed feature 3 (iso-C15 : 0 2-OH and/or C16 : 1ω7c; 17.2 %), iso-C15 : 0 (14.5 %) and summed feature 4 (anteiso-C17 : 1 B and/or iso-C17 : 1 I; 11.9 %). The DNA G+C content was 60.4 mol%. On the basis of the evidence presented in this study, strain HMD1010T represents a novel species of the genus Hymenobacter, for which the name Hymenobacter yonginensis sp. nov. was proposed. The type strain is HMD1010T ( = KCTC 22745T  = CECT 7546T).

Characterization of Hymenobacter isolates from Victoria Upper Glacier, Antarctica reveals five new species and substantial non-vertical evolution within this genus

We isolated several Hymenobacter-like strains from Victoria Upper Glacier, Antarctica, basal ice that diverged substantially from currently defined Hymenobacter species according to their 16S rRNA and gyrB gene phylogenies. All strains were psychrotolerant, heterotrophic aerobes which grew preferentially on low salt and low nutrient strength agar. Further phenotypic and chemotaxonomic characterization of these isolates supported their assignment as five novel species: H. algoricola sp. nov., H. antarcticus sp. nov., H. elongatus sp. nov., H. fastidiosus sp. nov., and H. glaciei sp. nov. Remarkable among these data was the prevalence of horizontal gene transfers and phenotypic variation, even between apparently closely related strains. These results suggest extensive non-vertical evolution within the genus Hymenobacter, and may reflect evolutionary trajectories resulting from dormancy, e.g., during interment in glacial ice.

Hymenobacter perfusus sp. nov., Hymenobacter flocculans sp. nov. and Hymenobacter metalli sp. nov. three new species isolated from an uranium mine waste water treatment system

Three red-pink pigmented strains, designated A1-12(T), A2-50A(T) and A2-91(T), were recovered from two different sites in a uranium mine. For all strains, the optimum growth temperature was 25°C, the optimum pH was 6.0-6.5 and the DNA G+C contents were between 60 and 63.4 mol%. The major respiratory quinone was menaquinone 7 (MK-7) and the fatty acid profiles contained iso- and anteiso-branched C15 fatty acids, summed feature 3 (16:1 ω6c and/or ω7c and/or 15:0 iso 2-OH), summed feature 4 (17:1 anteiso B and/or iso I) and the unsaturated fatty acid 16:1 ω5c as the major components. Phylogenetic analysis of the 16S rRNA gene sequences showed that these organisms represented three distinct branches within the family Flexibacteraceae most closely related to the members of the genus Hymenobacter. Strain A1-12(T) formed a distinct phylogenetic line along with H. rigui KCTC 12533(T) and they shared approximately 98.9% 16S rRNA gene sequence similarity. However, these two strains shared only 14.7% pairwise similarity in their genomic DNA. Strains A2-50A(T) and A2-91(T) formed two distinct lineages, related to the species H. soli KCTC 12607(T), sharing about 95.5% 16S rRNA gene sequence similarity between themselves, and 88.3 and 92.0% with other members of the genus Hymenobacter. Based on the phylogenetic analysis and physiological and biochemical characteristics, these isolates were considered to represent three novel species for which we propose the names Hymenobacter perfusus for strain A1-12(T) (=CIP 110166=LMG 26000), Hymenobacter flocculans for strain A2-50A(T) (=CIP 110139=LMG 25699) and Hymenobacter metalli for strain A2-91(T) (=CIP 110140=LMG 25700).

Hymenobacter psychrophilus sp. nov., a psychrophilic bacterium isolated from soil

A non-motile, rod-shaped, red-pigmented bacterium, designated strain BZ33r(T), was isolated from soil of an industrial site. Cells stained Gram-negative and were aerobic and psychrophilic, showing good growth at 1-20 °C. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain BZ33r(T) was related to members of the genus Hymenobacter and had highest sequence similarity with Hymenobacter aerophilus DSM 13606(T) (97.5 %). The predominant cellular fatty acids were anteiso-C(15 : 0) (20.3 %), summed feature 3 (C(16 : 1)ω7c and/or iso-C(15 : 0) 2-OH; 20.2 %), iso-C(15 : 0) (20.0 %), summed feature 4 (iso-C(17 : 1) I and/or anteiso-C(17 : 1) B; 8.2 %) and C(16 : 1)ω5c (7.9 %). Strain BZ33r(T) had MK-7 as the major menaquinone. The polyamine pattern contained sym-homospermidine as the major compound with moderate amounts of spermidine. Phosphatidylethanolamine, three unknown aminophospholipids, two unknown aminolipids, two unknown glycolipids and five unknown polar lipids were present in the polar lipid profile. The G+C content of the DNA was 61.6 mol%. On the basis of phenotypic characteristics, phylogenetic analysis and DNA-DNA relatedness data, strain BZ33r(T) is considered to represent a novel species of the genus Hymenobacter, for which the name Hymenobacter psychrophilus sp. nov. is proposed. The type strain is BZ33r(T) ( = DSM 22290(T)  = CGMCC 1.8975(T)  = LMG 25548(T)).

Microbial community structure, pigment composition, and nitrogen source of red snow in Antarctica

"Red snow" refers to red-colored snow, caused by bloom of cold-adapted phototrophs, so-called snow algae. The red snow found in Langhovde, Antarctica, was investigated from several viewpoints. Various sizes of rounded red cells were observed in the red snow samples under microscopy. Pigment analysis demonstrated accumulation of astaxanthin in the red snow. Community structure of microorganisms was analyzed by culture-independent methods. In the analyses of small subunit rRNA genes, several species of green algae, fungus, and various phylotypes of bacteria were detected. The detected bacteria were closely related to psychrophilic or psychrotolerant heterotrophic strains, or sequences detected from low-temperature environments. As predominant lineage of bacteria, members of the genus Hymenobacter were consistently detected from samples obtained in two different years. Nitrogen isotopic compositions analysis indicated that the red snow was significantly 15N-enriched. Based on an estimation of trophic level, it was suggested that primary nitrogen sources of the red snow were supplied from fecal pellet of seabirds including a marine top predator of Antarctica.