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

Dissemination of genes associated with antibiotic resistance and bacterial virulence during ecosystem succession in two Tibetan glacier forefields

The release of pathogens and DNA from the cryosphere (glacier, permafrost, and, sea ice) has become a new threat to society and environment. Due to enhanced glacier retreat, the size of glacier forefields has greatly expanded. Herein, we used a combination of metagenomic and metatranscriptomic methods and adopted a sequence-based approach to investigate the distribution and changing patterns of virulence factor genes (VFGs) and antibiotic resistance genes (ARGs) in two glacier forefields. The forefields are separated by approximately 400 km located in the center and north of the Tibetan Plateau, which are used to demonstrate the gene dissemination capacity across short (10 m) and long (730 m) spatial transects. The results revealed a diverse range of actively transcribed VFGs and ARGs. The relative abundance of ARG reduced with ecosystem succession, while that of VFG was similar, suggesting that the ARG is under a stronger environmental selection pressure. VFGs and ARGs were dominated by those associated with adherence and vancomycin resistance, respectively. Notably, toxin production related genes were identified but a low abundance, indicating a low risk to health in glacier forefields. The dissemination risks were low for both VFGs and ARGs, which was strongly constrained by dispersal limitation. Additionally, the limited dissemination was mainly through vertical transmission, instead of horizontal transfer. In conclusion, the sequence-based approach revealed a low risk to health in recently deglaciated areas, with the risk of VFGs and ARGs being disseminated into downstream ecosystems remaining low.

Taxonomic and functional characterization of biofilms from a photovoltaic panel reveals high genetic and metabolic complexity of the communities

AIMS

Biofilms are complex microbial cell aggregates that attach to different surfaces in nature, industrial environments, or hospital settings. In photovoltaic panels (PVs), biofilms are related to significant energy conversion losses. In this study, our aim was to characterize the communities of microorganisms and the genes involved in biofilm formation.

METHODS AND RESULTS

In this study, biofilm samples collected from a PV system installed in southeastern Brazil were analyzed through shotgun metagenomics, and the microbial communities and genes involved in biofilm formation were investigated. A total of 2030 different genera were identified in the samples, many of which were classified as extremophiles or producers of exopolysaccharides. Bacteria prevailed in the samples (89%), mainly the genera Mucilaginibacter, Microbacterium, Pedobacter, Massilia, and Hymenobacter. The functional annotation revealed >12 000 genes related to biofilm formation and stress response. Genes involved in the iron transport and synthesis of c-di-GMP and c-AMP second messengers were abundant in the samples. The pathways related to these components play a crucial role in biofilm formation and could be promising targets for preventing biofilm formation in the PV. In addition, Raman spectroscopy analysis indicated the presence of hematite, goethite, and ferrite, consistent with the mineralogical composition of the regional soil and metal-resistant bacteria.

CONCLUSIONS

Taken together, our findings reveal that PV biofilms are a promising source of microorganisms of industrial interest and genes of central importance in regulating biofilm formation and persistence.

The distinctive weathering crust habitat of a High Arctic glacier comprises discrete microbial micro-habitats

Sunlight penetrates the ice surfaces of glaciers and ice sheets, forming a water-bearing porous ice matrix known as the weathering crust. This crust is home to a significant microbial community. Despite the potential implications of microbial processes in the weathering crust for glacial melting, biogeochemical cycles, and downstream ecosystems, there have been few explorations of its microbial communities. In our study, we used 16S rRNA gene sequencing and shotgun metagenomics of a Svalbard glacier surface catchment to characterise the microbial communities within the weathering crust, their origins and destinies, and the functional potential of the weathering crust metagenome. Our findings reveal that the bacterial community in the weathering crust is distinct from those in upstream and downstream habitats. However, it comprises two separate micro-habitats, each with different taxa and functional categories. The interstitial porewater is dominated by Polaromonas, influenced by the transfer of snowmelt, and exported via meltwater channels. In contrast, the ice matrix is dominated by Hymenobacter, and its metagenome exhibits a diverse range of functional adaptations. Given that the global weathering crust area and the subsequent release of microbes from it are strongly responsive to climate projections for the rest of the century, our results underscore the pressing need to integrate the microbiome of the weathering crust with other communities and processes in glacial ecosystems.

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.

Developing a bioinformatics pipeline for comparative protein classification analysis

BACKGROUND

Protein classification is a task of paramount importance in various fields of biology. Despite the great momentum of modern implementation of protein classification, machine learning techniques such as Random Forest and Neural Network could not always be used for several reasons: data collection, unbalanced classification or labelling of the data.As an alternative, I propose the use of a bioinformatics pipeline to search for and classify information from protein databases. Hence, to evaluate the efficiency and accuracy of the pipeline, I focused on the carotenoid biosynthetic genes and developed a filtering approach to retrieve orthologs clusters in two well-studied plants that belong to the Brassicaceae family: Arabidopsis thaliana and Brassica rapa Pekinensis group. The result obtained has been compared with previous studies on carotenoid biosynthetic genes in B. rapa where phylogenetic analysis was conducted.

RESULTS

The developed bioinformatics pipeline relies on commercial software and multiple databeses including the use of phylogeny, Gene Ontology terms (GOs) and Protein Families (Pfams) at a protein level. Furthermore, the phylogeny is coupled with "population analysis" to evaluate the potential orthologs. All the steps taken together give a final table of potential orthologs. The phylogenetic tree gives a result of 43 putative orthologs conserved in B. rapa Pekinensis group. Different A. thaliana proteins have more than one syntenic ortholog as also shown in a previous finding (Li et al., BMC Genomics 16(1):1-11, 2015).

CONCLUSIONS

This study demonstrates that, when the biological features of proteins of interest are not specific, I can rely on a computational approach in filtering steps for classification purposes. The comparison of the results obtained here for the carotenoid biosynthetic genes with previous research confirmed the accuracy of the developed pipeline which can therefore be applied for filtering different types of datasets.

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.

Hymenobacter terricola sp. nov., isolated from Antarctic soil

Strain 3F2T was isolated from a soil sample obtained from the surface of Deception Island, Antarctica. The isolate was a Gram-stain-negative, aerobic, non-motile, rod-shaped bacterium, and its colonies were red to pink in colour. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 3F2T belonged to the genus Hymenobacter , family Hymenobacteraceae and was most closely related to Hymenobacter sedentarius DG5BT (97.0% sequence similarity), Hymenobacter soli PB17T (96.9%), Hymenobacter terrae DG7AT (96.8%) and Hymenobacter rufus S1-2-2-6T (96.5%). Growth occurred at 4–20 °C (optimum, 10 °C), up to 1.0 % (w/v) NaCl (optimum, 0%) and pH 6.0–8.0 (optimum, pH 7.0). The chemotaxonomic characteristics of strain 3F2T, which had MK-7 as its predominant menaquinone and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c), iso-C15:0, anteiso-C15:0 and C16:1 ω5c as its major fatty acids, were consistent with classification in the genus Hymenobacter . The polar lipid profile of strain 3F2T comprised phosphatidylethanolamine, two unidentified aminolipids, two unidentified aminophospholipids and three unidentified polar lipids. The genome of strain 3F2T was 6.56 Mbp with a G+C content of 61.5 mol%. Average nucleotide identity (ANI) values between 3F2T and the other species of the genus Hymenobacter were found to be low (ANIm <87.0%, ANIb <82.0% and OrthoANIu <83.0%). Furthermore, digital DNA–DNA hybridization and average amino acid identity values between strain 3F2T and the closely related species ranged from 20.0 to 26.3% and from 64.0 to 81.1 %, respectively. Based on the results of our phylogenetic, phenotypic, genotypic and chemotaxonomic analyses, it is concluded that strain 3F2T represents a novel species within the genus Hymenobacter , for which the name Hymenobacter terricola sp. nov. is proposed. The type strain is 3F2T (=KCTC 72468T=CGMCC 1.13716T).

Functional filtering and random processes affect the assembly of microbial communities of snow algae blooms at Maritime Antarctic

The increasing temperatures at the West Antarctic Peninsula (Maritime Antarctic) could lead to a higher occurrence of snow algal blooms which are ubiquitous events that change the snow coloration, reducing albedo and in turn exacerbating melting. However, there is a limited understanding of snow algae blooms biodiversity, composition, and their functional profiles, especially in one of the world's areas most affected by climate change. In this study we used 16S rRNA and 18S rRNA metabarcoding, and shotgun metagenomics to assess the diversity, composition, and functional potential of the snow algae blooms bacterial and eukaryotic communities at three different sites of Maritime Antarctic, between different colors of the algae blooms and between seasonal and semi-permanent snowfields. We tested the hypothesis that the functional potential of snow algae blooms is conserved despite a changing taxonomic composition. Furthermore, we determined taxonomic co-occurrence patterns of bacteria and eukaryotes and assessed the potential for the exchange of metabolites among bacterial taxa. Here, we tested the prediction that there are co-occurring taxa within snow algae whose biotic interactions are marked by the exchange of metabolites. Our results show that the composition of snow algae blooms vary significantly among sites. For instance, a higher abundance of fungi and protists were detected in Fildes Peninsula compared with Doumer Island and O'Higgins. Likewise, the composition varied between snow colors and snow types. However, the functional potential varied only among sampling sites with a higher abundance of genes involved in tolerance to environmental stress at O'Higgins. Co-occurrence patterns of dominant bacterial genera such as Pedobacter, Polaromonas, Flavobacterium and Hymenobacter were recorded, contrasting the absence of co-occurring patterns displayed by Chlamydomonadales algae with other eukaryotes. Finally, genome-scale metabolic models revealed that bacteria within snow algae blooms likely compete for resources instead of forming cooperative communities.

Hymenobacter telluris sp. nov., isolated from soil in South Korea

Two novel bacterial strains, designated as BT186^T and BT505, were isolated from a soil sample collected in South Korea and characterized. Both strains were Gram-stain-negative, rod-shaped, aerobic, circular, convex, and had red-colored colonies. The level of 16S rRNA gene sequence similarity between the strains BT186^T and BT505 was 100%, indicating that they represent an identical species. 16S rRNA sequence analysis indicated that strains BT186^T and BT505 belong to a distinct lineage within the genus Hymenobacter (family Hymenobacteraceae, order Cytophagales, class Cytophagia, phylum Bacteroidetes, Kingdom Bacteria). Both strains were closely related to Hymenobacter norwichensis DSM 15439^T (98.3% 16S rRNA gene similarity), Hymenobacter aquaticus JCM 31653^T (96.8%), and Hymenobacter perfusus LMG26000^T (96.5%). Strain BT186^T was found to have the MK-7 as the major respiratory quinone. The major polar lipid of strain BT186^T was identified to be phosphatidylethanolamine (PE). The major cellular fatty acid profiles of strain BT186^T were C_16:1 ω5c (24.3%), iso-C_15:0 (20.3%) and summed feature 3 (C_16:1 ω6c/C_16:1 ω7c) (19.9%). Characterization based on polyphasic analysis indicated that strains BT186^T and BT505 represent novel species of the genus Hymenobacter and the name Hymenobacter telluris sp. nov. is proposed. The type strain of Hymenobacter telluris is BT186^T (= KCTC 72338^T = NBRC 114968^T).

Spatial and Annual Variation in Microbial Abundance, Community Composition, and Diversity Associated With Alpine Surface Snow

Understanding microbial community dynamics in the alpine cryosphere is an important step toward assessing climate change impacts on these fragile ecosystems and meltwater-fed environments downstream. In this study, we analyzed microbial community composition, variation in community alpha and beta diversity, and the number of prokaryotic cells and virus-like particles (VLP) in seasonal snowpack from two consecutive years at three high altitude mountain summits along a longitudinal transect across the European Alps. Numbers of prokaryotic cells and VLP both ranged around 104 and 105 per mL of snow meltwater on average, with variation generally within one order of magnitude between sites and years. VLP-to-prokaryotic cell ratios spanned two orders of magnitude, with median values close to 1, and little variation between sites and years in the majority of cases. Estimates of microbial community alpha diversity inferred from Hill numbers revealed low contributions of common and abundant microbial taxa to the total taxon richness, and thus low community evenness. Similar to prokaryotic cell and VLP numbers, differences in alpha diversity between years and sites were generally relatively modest. In contrast, community composition displayed strong variation between sites and especially between years. Analyses of taxonomic and phylogenetic community composition showed that differences between sites within years were mainly characterized by changes in abundances of microbial taxa from similar phylogenetic clades, whereas shifts between years were due to significant phylogenetic turnover. Our findings on the spatiotemporal dynamics and magnitude of variation of microbial abundances, community diversity, and composition in surface snow may help define baseline levels to assess future impacts of climate change on the alpine cryosphere.

Hymenobacter taeanensis sp. nov., radiation resistant bacterium isolated from coastal sand dune

An aerobic, Gram-stain-negative, non-motile, non-spore-forming, rod-shaped, and light pink-colored bacterial strain, designated TS19^T, was isolated from a sand sample obtained from a coastal sand dune after exposure to 3 kGy of gamma radiation. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the isolate was a member of the genus Hymenobacter and was most closely related to H. wooponensis WM78^T (98.3% similarity). Strain TS19^T and H. wooponensis showed resistance to gamma radiation with D₁₀ values (i.e., the dose required to reduce the bacterial population by tenfold) of 7.3 kGy and 3.5 kGy, respectively. The genome of strain TS19^T consists of one contig with 4,879,662 bp and has a G + C content of 56.2%. The genome contains 3,955 protein coding sequences, 44 tRNAs, and 12 rRNAs. The predominant fatty acids of strain TS19^T were iso-C_15:0, summed feature 4 (iso-C_17:1 I and/or anteiso-C_17:1 B), summed feature 3 (C_16:1 ω6c and/or C_16:1 ω7c), and C_16:1 ω5c. The major polar lipids were phosphatidylethanolamine, and one unidentified aminophospholipid. The main respiratory quinone was menaquinone-7. Based on the phylogenetic, physiological, and chemotaxonomic characteristics, strain TS19^T represents a novel species, for which the name Hymenobacter taeanensis sp. nov. is proposed. The type strain is TS19^T (= KCTC 72897^T = JCM 34023^T).

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 caeli sp. nov., an airborne bacterium isolated from King George Island, Antarctica

A rod-shaped and Gram-stain-negative bacterial strain 9A^T, was isolated from an air sample collected at King George Island, maritime Antarctica. Phylogenetic analysis based on 16S rRNA gene sequence reveals that strain 9A^T belongs to the genus Hymenobacter and shows the highest similarity to Hymenobacter coccineus CCM 8649^T (96.8 %). The DNA G+C content based on the draft genome sequence is 64.9 mol%. Strain 9A^T is strictly aerobic, psychrophilic, catalase-positive, oxidase-positive and non-motile. Growth is observed at 0-20 °C (optimum 10 °C), pH 6.0-8.0 (optimum pH 7.0), and in the absence of NaCl. The predominant menaquinone of strain 9A^T is MK-7 and the major fatty acids comprise Summed Feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c; 25.2 %), iso-C_15 : 0 (23.2 %), C_16 : 1  ω5c (11.6 %), Summed Feature 4 (anteiso-C_17 : 1 B/iso-C_17 : 1 I) (9.6 %) and anteiso-C_15 : 0 (9.6 %). The polar lipid profile consists of the major lipid phosphatidylethanolamine and moderate to minor amounts of phosphatidylserine, unidentified aminolipids, aminophospholipids, aminophosphoglycolipids, polar lipids lacking a functional group and an unidentified phospholipid and a glycolipid. In the polyamine pattern sym-homospermidine is predominant. On the basis of the results obtained, strain 9A^T is proposed as a novel species of the genus Hymenobacter, for which the name Hymenobacter caeli sp. nov. is suggested. The type strain is 9A^T (=CCM 8971^T=LMG 32109^T=DSM 111653^T).

Climate change, melting cryosphere and frozen pathogens: Should we worry…?

Permanently frozen environments (glaciers, permafrost) are considered as natural reservoirs of huge amounts of microorganisms, mostly dormant, including human pathogens. Due to global warming, which increases the rate of ice-melting, approximately 4 × 1021 of these microorganisms are released annually from their frozen confinement and enter natural ecosystems, in close proximity to human settlements. Some years ago, the hypothesis was put forward that this massive release of potentially-pathogenic microbes-many of which disappeared from the face of the Earth thousands and even millions of years ago-could give rise to epidemics. The recent anthrax outbreaks that occurred in Siberia, and the presence of bacterial and viral pathogens in glaciers worldwide, seem to confirm this hypothesis. In that context, the present review summarizes the currently available scientific evidence that allows us to imagine a near future in which epidemic outbreaks, similar to the abovementioned, could occur as a consequence of the resurrection and release of microbes from glaciers and permafrost.

Supplementary Information

The online version of this article (10.1007/s42398-021-00184-8) contains supplementary material, which is available to authorized users.

Hymenobacter negativus sp. nov., bacteria isolated from mountain soil collected in South Korea

Two novel Gram-negative bacterial strains BT442^T and BT584 were isolated from dry soil collected in mountains Busan and Guri, Korea during wintertime. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strains BT442^T and BT584 both belong to a distinct lineage within the genus Hymenobacter (family Hymenobacteraceae, order Cytophagales, class Cytophagia). Strain BT442^T was closely related to Hymenobacter soli PB17^T (98.0% 16S rRNA gene similarity) and Hymenobacter terrae POA9^T (97.6%). No other recognized bacterial species showed more than 97% 16S rRNA gene sequence similarity to strains BT442^T. The genome size of strain BT442^T was 5,143,362 bp. Bacterial growth was observed at 10-30 °C (optimum 25 °C), pH 6.0-8.0 (optimum pH 6.0) in R2A agar and in the presence up to 1% NaCl. The major cellular fatty acids of strains BT442^T and BT584 were iso-C_15:0, anteiso-C_15:0 and summed feature 3 (C_16:1 ω6c / C_16:1 ω7c). In addition, their predominant respiratory quinone was MK-7. The major polar lipids of strains BT442^T and BT584 were identified to be phosphatidylethanolamine, aminophospholipid, and aminolipid. Based on the biochemical, chemotaxonomic, and phylogenetic analyses, strains BT442^T and BT584 are novel bacterial species within the genus Hymenobacter, and the proposed name is Hymenobacter negativus. The strain type of Hymenobacter negativus is BT442^T (= KCTC 72902^T = NBRC XXXX^T).

Pigments from Antarctic bacteria and their biotechnological applications

Pigments from microorganisms have triggered great interest in the market, mostly by their "natural" appeal, their favorable production conditions, in addition to the potential new chemical structures or naturally overproducing strains. They have been used in: food, feed, dairy, textile, pharmaceutical, and cosmetic industries. The high rate of pigment production in microorganisms recovered from Antarctica in response to selective pressures such as: high UV radiation, low temperatures, and freezing and thawing cycles makes this a unique biome which means that much of its biological heritage cannot be found elsewhere on the planet. This vast arsenal of pigmented molecules has different functions in bacteria and may exhibit different biotechnological activities, such as: extracellular sunscreens, photoprotective function, antimicrobial activity, biodegradability, etc. However, many challenges for the commercial use of these compounds have yet to be overcome, such as: the low stability of natural pigments in cosmetic formulations, the change in color when subjected to pH variations, the low yield and the high costs in their production. This review surveys the different types of natural pigments found in Antarctic bacteria, classifying them according to their chemical structure. Finally, we give an overview of the main pigments that are used commercially today.

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.

Isolation and characterization of fast-growing green snow bacteria from coastal East Antarctica

Snow microorganisms play a significant role in climate change and affecting the snow melting rate in the Arctic and Antarctic regions. While research on algae inhabiting green and red snow has been performed extensively, bacteria dwelling in this biotope have been studied to a much lesser extent. In this study, we performed 16S rRNA gene amplicon sequencing of two green snow samples collected from the coastal area of the eastern part of Antarctica and conducted genotypic and phenotypic profiling of 45 fast-growing bacteria isolated from these samples. 16S rRNA gene amplicon sequencing of two green snow samples showed that bacteria inhabiting these samples are mostly represented by families Burkholderiaceae (46.31%), Flavobacteriaceae (22.98%), and Pseudomonadaceae (17.66%). Identification of 45 fast-growing bacteria isolated from green snow was performed using 16S rRNA gene sequencing. We demonstrated that they belong to the phyla Actinobacteria and Proteobacteria, and are represented by the genera Arthrobacter, Cryobacterium, Leifsonia, Salinibacterium, Paeniglutamicibacter, Rhodococcus, Polaromonas, Pseudomonas, and Psychrobacter. Nearly all bacterial isolates exhibited various growth temperatures from 4°C to 25°C, and some isolates were characterized by a high level of enzymatic activity. Phenotyping using Fourier transform infrared (FTIR) spectroscopy revealed a possible accumulation of intracellular polymer polyhydroxyalkanoates (PHA) or lipids in some isolates. The bacteria showed different lipids/PHA and protein profiles. It was shown that lipid/PHA and protein spectral regions are the most discriminative for differentiating the isolates.

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).

Resurrection of inactive microbes and resistome present in the natural frozen world: Reality or myth?

The present world faces a new threat of ancient microbes and resistomes that are locked in the cryosphere and now releasing upon thawing due to climate change and anthropogenic activities. The cryosphere act as the best preserving place for these microbes and resistomes that stay alive for millions of years. Current reviews extensively discussed whether the resurrection of microbes and resistomes existing in these pristine environments is true or just a hype. Release of these ancient microorganisms and naked DNA is of great concern for society as these microbes can either cause infections directly or they can interact with contemporary microorganisms and affect their fitness, survival, and mutation rate. Moreover, the contemporary microorganisms may uptake the unlocked naked DNA, which might transform non-pathogenic microorganisms into deadly antibiotic-resistant microbes. Additionally, the resurrection of glacial microorganisms can cause adverse effects on ecosystems downstream. The release of glacial pathogens and naked DNA is real and can lead to fatal outbreaks; therefore, we must prepare ourselves for the possible reemergence of diseases caused by these microbes. This study provides a scientific base for the adoption of actions by international cooperation to develop preventive measures.

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).

Validating biochemical features at the genome level in the Antarctic bacterium Hymenobacter sp. strain UV11

We present experimental data that complement and validate some biochemical features at the genome level in the UVC-resistant Antarctic bacterium Hymenobacter sp. UV11 strain. The genome was sequenced, assembled and annotated. It has 6 096 246 bp, a GC content of 60.6% and 5155 predicted genes. The secretome analysis, by combining in silico predictions with shotgun proteomics data, showed that UV11 strain produces extracellular proteases and carbohydrases with potential biotechnological uses. We observed the formation of outer membrane vesicles, mesosomes and carbon-storage compounds by using transmission electron microscopy. The in silico analysis of the genome revealed the presence of genes involved in the metabolism of glycogen-like molecules and starch. By HPLC-UV-Vis analysis and 1H-NMR spectra, we verified that strain UV11 produces xanthophyll-like carotenoids such as 2'-hydroxyflexixanthin, and the in silico analysis showed that this bacterium has genes involved in the biosynthesis of cathaxanthin, zeaxanthin and astaxanthin. We also found genes involved in the repair of UV-damaged DNA such as a photolyase, the nucleotide excision repair system and the production of ATP-dependent proteases that are important cellular components involved in the endurance to physiological stresses. This information will help us to better understand the ecological role played by Hymenobacter strains in the extreme Antarctic environment.

Hymenobacter lutimineralis sp. nov., belonging to the family Hymenobacteraceae, isolated from zeolite

A red-pigmented bacterial strain, designated KIGAM108^T, within the family Hymenobacteraceae was isolated from zeolite in the Gampo-41 mine of the Gyeongju, Republic of Korea. This strain was a Gram-negative, strictly aerobic, non-spore forming, rod-shaped bacterium. Phylogenetic analysis of the 16S rRNA gene sequence of strain KIGAM108^T found that it was related to the genus Hymenobacter, with similarities of 96.6, 96.4, 95.5, and 95.0% to H. fastidiosus VUG-A124^T, H. algoricola VUG-A23a^T, H. crusticola MIMBbqt21^T, and H. daecheongensis DSM 21074^T, respectively. Strain KIGAM108^T grew in the presence of 0-0.5% (w/v) NaCl at 4-37 °C and pH 6.0-10.0. This isolate contained MK-7 as a respiratory quinone. The polar lipids of strain KIGAM108^T were identified as phosphatidylethanolamine, two unidentified aminophospholipids, one unidentified phospholipid and five unidentified lipids. The major fatty acids profile showed summed feature 3 (C_16:1ω6c and/or C_16:1ω7c) (22.3%), anteiso-C_15:0 (17.1%), C_16:1ω5c (13.3%), and iso-C_15:0 (11.0%). The genomic DNA G + C content was 60.0 mol%. Based on the polyphasic taxonomic data, strain KIGAM108^T is considered to represent a novel species of the genus Hymenobacter, for which the name Hymenobacter lutimineralis sp. nov. is proposed. The type strain is KIGAM108^T (=KCTC 72263^T =JCM 33444^T).

Hymenobacter jejuensis sp. nov., a UV radiation-tolerant bacterium isolated from Jeju Island

A novel Gram-stain negative, aerobic, rod-shaped, non-motile and pink-coloured bacterium, designated strain 17J68-5^T, was isolated from soil in Jeju Island, Korea. The strain was found to grow at 18-37 °C (optimum 25 °C) in R2A medium at pH (6.0 to 7.5; optimum 6.5) in the presence of 0% (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain 17J68-5^T forms a distinct lineage within the family Hymenobacteraceae and is closely related to Hymenobacter daecheongensis DSM 21074^T (94.9% 16S rRNA gene sequence similarity), Hymenobacter rutilus K2-33028^T (94.6%) and Hymenobacter tibetensis XTM003^T (94.3%). The draft genome sequence of strain 17J68-5^Tis 5.1 Mb size. The calculated average nucleotide identity and the digital DNA-DNA hybridization between strain 17J68-5^T and closely related type strains were 81.3 to 84.1  % and 25.5 to 28.1%. The major cellular fatty acids (≥ 10%) of the strain 17J68-5^T were identified as summed feature 3 (C_16:1ω6c/C_16:1ω7c; 21.2%), iso-C_15:0 (19.1%), summed feature 4 (C_17:1 iso I/C_17:1 anteiso B; 17.9%) and C_16:1ω5c (13.1%). The predominant respiratory quinones were found to be menaquinone 7 and 6 (MK-7 and MK-6). The major polar lipid was found to be phosphatidylethanolamine. The genomic DNA G + C content based on the whole genome sequence is 59.6 mol %. The phenotypic, chemotaxonomic and genotypic properties clearly indicated that isolate 17J68-5^T represents a novel species within the genus Hymenobacter, for which the name Hymenobacter jejuensis sp. nov. is proposed. The type strain of Hymenobacter jejuensis is 17J68-5^T (= KCTC 62224^T = JCM 33182^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).

Antarctic heterotrophic bacterium Hymenobacter nivis P3T displays light-enhanced growth and expresses putative photoactive proteins

Hymenobacter nivis P3^T is a heterotrophic bacterium isolated from Antarctic red snow generated by algal blooms. Despite being non-photosynthetic, H. nivis was dominantly found in the red snow environment that is exposed to high light and UV irradiation, suggesting that this species can flourish under such harsh conditions. In order to further understand the adaptive strategies on the snow surface environment of Antarctica, the genome of H. nivis P3^T was sequenced and analyzed, which identified genes putatively encoding for light-reactive proteins such as proteorhodopsin, phytochrome, photolyase and several copies of cryptochromes. Culture-based experiments revealed that H. nivis P3^T growth was significantly enhanced under light conditions, while dark conditions had increased extracellular polymeric substances. Furthermore, the expression of several putative light-reactive proteins was determined by proteomic analysis. These results indicate that H. nivis P3^T is able to potentially utilize light, which may explain its dominance on the red snow surface environment of Antarctica. ORIGINALITY-SIGNIFICANCE STATEMENT: The role of proteorhodopsin in heterotrophic bacteria is not well-characterized, as only a handful of proteorhodopsin-harbouring isolates were shown to have a light-enhanced phenotype through culture-based experiments to date. This is the first study that demonstrates light-stimulated growth and protein expression evidence of photoactive proteins for a non-marine psychrophile and for a member of the genus Hymenobacter. It is also the first study that provides comprehensive proteome information for this genus. This study presents significant results in understanding the adaptive mechanism of a heterotrophic non-photosynthetic bacterium thriving on the snow surface environment of Antarctica as well as demonstrating the role of light-utilization in promoting growth, possibly through proteorhodopsin.

Hymenobacter persicinus sp. nov., a novel member of the family Hymenobacteraceae

A bacterial strain, 1-3-3-3^T, was isolated from a soil sample collected in Jeollabuk-do province, South Korea. Cells were observed to be Gram-stain negative, short rod-shaped and colonies to be red-pink in colour. Analysis of 16S rRNA gene sequences identified this strain as a member of the genus Hymenobacter in the family Hymenobacteraceae, with high levels of 16S rRNA sequence similarity with Hymenobacter algoricola VUG-A23a^T (98.0%), Hymenobacter knuensis 16F7C-2 (97.9%), Hymenobacter fastidiosus VUG-A124^T (97.1%), Hymenobacter elongatus VUG-A112^T (97.0%), Hymenobacter chitinivorans Txc1^T (97.0%) and Hymenobacter aquaticus 16F3P^T (96.7%). Growth of strain 1-3-3-3^T was observed at 10-30 °C, pH 6-8 and in the presence of 0-1.0% NaCl. The genomic G + C content was determined to be 61.6 mol %. The predominant respiratory quinone of the isolate was found to be MK-7; the major fatty acids were identified as iso-C_15:0 (19.9%), summed feature 3 (C_16:1ω7c/C_16:1ω6c, 19.7%), summed feature 4 (iso-C_17:1 I/anteiso-C_17:1 B, 17.8%), C_16:1ω5c (12.5%) and anteiso-C_15:0 (11.2%), and the major polar lipid was found to be phosphatidylethanolamine. The phenotypic and chemotaxonomic data support the affiliation of strain 1-3-3-3^T with the genus Hymenobacter. However, the DNA-DNA relatedness between the isolate and its closest phylogenetic neighbours was lower than 34%. The DNA-DNA hybridization result and the differentiating phenotypic properties clearly indicate that strain 1-3-3-3^T represents a novel species in the genus Hymenobacter, for which the name Hymenobacter persicinus sp. nov. is proposed. The type strain is 1-3-3-3^T (= KCTC 52742^T = JCM 32191^T).

Hymenobacter crusticola sp. nov., isolated from biological soil crust

A Gram-stain-negative, aerobic, light-pink, short rod-shaped, non-spore-forming bacterial strain was isolated from biological soil crust sampled in the Hopq Desert, Inner Mongolia, China, designated MIMBbqt21^T. The G+C content of the genomic DNA was 55.1 mol%. Phylogenetic analysis of the 16S rRNA gene sequence showed that strain MIMBbqt21^T belonged to the genus Hymenobacter and had the highest sequence similarity to Hymenobacter cavernaeK1E01-27^T (94.35 %). Cell growth could be observed at 4-29 °C (optimum, 24 °C), pH of 6.0-8.6 (optimum, 6.0) and in the presence of 1 % (w/v) NaCl (optimum, 0 %). The major fatty acids of strain MIMBbqt21^T were iso-C15 : 0, C16 : 1ω5c and summed feature 3 (C16 : 1ω7c/C16 : 1ω6c). The main polar lipids were phosphatidylethanolamine, five unidentified aminophospholipids, an unidentified glycolipid and four unidentified polar lipids. The sole respiratory quinone was menaquinone MK-7. Based on the results of the phylogenetic, chemotaxonomic and phenotypic studies, strain MIMBbqt21^T could be distinguished from all known Hymenobacter species and represents a novel species, for which the name Hymenobactercrusticola sp. nov. is proposed. The type strain is MIMBbqt21^T (=MCCC 1K01312^T=KCTC 42804^T).

Hymenobacter pomorum sp. nov., Isolated from Apple Orchard Soil

A Gram-stain-negative, non-motile, rod-shaped bacterial strain, designated 9-2-1-1^T, was isolated from apple orchard soil in Daegu, Republic of Korea. Comparative 16S rRNA gene sequence analysis showed that the isolate belongs to the family Cytophagaceae, Bacteroidetes and it is most closely related to Hymenobacter metalli A2-91^T (97.8% similarity) and Hymenobacter marinus KJ035^T (96.6%). Growth of strain 9-2-1-1^T was observed at 4-30 °C, pH 6-8, and in the presence of 0-1.0% NaCl. The G+C content of the genomic DNA was 62.0 mol%. The predominant respiratory quinone of the isolate was MK-7; the major fatty acids were C_15:0 iso (29.3%), C_16:1ω5c (15.4%), C_15:0 anteiso (12.5%), summed feature 3 (C_16:1ω7c/C_16:1ω6c; 12.3%), and C_16:0 (10.6%); and the major polar lipid was phosphatidylethanolamine. The phenotypic and chemotaxonomic data supported the affiliation of strain 9-2-1-1^T with the genus Hymenobacter. However, the DNA-DNA relatedness between the isolate and H. metalli and H. marinus were 31.3% and 24.7%, respectively. The DNA-DNA hybridization result and the differentiating phenotypic properties clearly indicate that strain 9-2-1-1^T is the representative of a novel species in the genus Hymenobacter, for which the name Hymenobacter pomorum sp. nov. is proposed. The type strain is 9-2-1-1^T (=KCTC 52740^T = JCM 32193^T).

Hymenobacter rufus sp. nov., a bacterium isolated from soil

A bacterial strain, S1-2-2-6^T, was isolated from a soil sample collected in Jeollabuk-do province, Republic of Korea. Cells of this strain were observed to be Gram-stain-negative, short and rod-shaped, and colonies were red to pink in colour. Analysis of 16S rRNA gene sequences identified this strain as representing a member of the genus Hymenobacter in the family Cytophagaceae, with the highest levels of sequence similarity being observed in relation to Hymenobacter terrae DG7A^T (98.2 %), Hymenobacter rubidus DG7B^T (97.9 %), Hymenobacter soli PB17^T (97.7 %), and Hymenobacter daeguensis 16F3Y-2^T (97.3 %). Growth of S1-2-2-6^T was observed at 4-30 °C, pH 6-8 and in the presence of 0-0.5 % NaCl. The predominant respiratory quinone of this strain was menaquinone-7, the major fatty acids were C15 : 0 iso, C15 : 0 anteiso, and Summed feature 3 (C16 : 1ω7c/C16 : 1ω6c), and the major polar lipid was phosphatidylethanolamine. The genomic DNA G+C content of S1-2-2-6^T was 60.7 mol%. DNA-DNA hybridization experiments with H. terrae, H. rubidus, H. soli and H. daeguensisresulted in relatedness values of 35.9 and 38.4 %, 34.2 and 30.4 %, 28.3 and 33.1 %, and 23.5 and 27.9 %, respectively. These DNA-DNA hybridization results, in addition to some differentiating phenotypic properties, clearly indicate that S1-2-2-6^T is a representative of a novel species of the genus Hymenobacter, for which the name Hymenobacter rufus sp. nov. is proposed. The type strain is S1-2-2-6^T (=KCTC 52736^T=JCM 32196^T).

Hymenobacter jeollabukensis sp. nov., isolated from soil

A Gram-stain-negative, non-motile, rod-shaped, aerobic bacterial strain, designated 1-3-3-8^T, was isolated from soil and characterized taxonomically using a polyphasic approach. Comparative 16S rRNA gene sequence analysis showed that strain 1-3-3-8^T belongs to the family Cytophagaceae of phylum Bacteroidetes and is most closely related to Hymenobacter paludis KBP-30^T (96.8% similarity), Hymenobacter ocellatus Myx2105^T (96.8%), Hymenobacter coalescens WW84^T (95.6%), and Hymenobacter deserti ZLB-3^T (95.4%). The G + C content of the genomic DNA of strain 1-3-3-8^T was 63.6 mol%. The isolate contained C_15:0 iso (28.4%), summed feature 4 (C_17:1 anteiso B/C_17:1 iso I; 18.9%), and C_15:0 anteiso (17.6%) as major fatty acids, MK-7 as the predominant respiratory quinone, and sym-homospermidine as the predominant polyamine. The major polar lipids were phosphatidylethanolamine and an unidentified lipid. The phenotypic and chemotaxonomic data supported the affiliation of strain 1-3-3-8^T with the genus Hymenobacter. The DNA-DNA relatedness between strain 1-3-3-8^T and H. paludis KCTC 32237^T and H. ocellatus DSM 11117^T were 24.5 and 27.4% respectively, clearly showing that the isolate is not related to them at the species level. Overall, the novel strain could be differentiated from its phylogenetic neighbors on the basis of several phenotypic, genotypic, and chemotaxonomic features. Therefore, strain 1-3-3-8^T represents a novel species of the genus Hymenobacter, for which the name Hymenobacter jeollabukensis sp. nov. has been proposed. The type strain is 1-3-3-8^T (= KCTC 52741^T = JCM 32192^T).

Description of Hymenobacter daejeonensis sp. nov., isolated from grass soil, based on multilocus sequence analysis of the 16S rRNA gene, gyrB and tuf genes

A polyphasic taxonomic study was carried out on strains PB105^T and PB108 isolated from a grass soil in Korea. The cells of the strains were Gram-stain negative, non-spore-forming, non-motile, and rod-shaped. Comparative 16S rRNA gene sequence studies showed a clear affiliation of these strains with Bacteroidetes, which showed high pairwise sequence similarities with Hymenobacter algoricola VUG-A23a^T (99.2%), Hymenobacter fastidiosus VUG-A124a^T (97.4%), and Hymenobacter daecheongensis Dae14^T (96.9%). The phylogenetic analysis based on 16S rRNA gene sequences showed that the strains formed a clear phylogenetic lineage with the genus Hymenobacter. The major fatty acids were identified as C_15:0 iso, C_15:0 anteiso, C_16:1 ω5c, C_15:0 iso 3-OH, C_17:0 iso 3-OH, summed feature 3 (C_16:1 ω6c and/or C_16:1 ω7c/t), and summed feature 4 (C_17:1 anteiso B and/or C_17:1 iso I). The major cellular polar lipids were identified as phosphatidylethanolamine, an unidentified aminolipid, and two unidentified lipids. The respiratory quinone was identified as MK-7 and the genomic DNA G+C content was determined to be 64.5 mol% for strain PB105^T and 64.1 mol% for strain PB108. DNA-DNA hybridization value of type strain PB105^T with H. algoricola VUG-A23a^T was 32.3% (reciprocal 39.2). Based on the combined genotypic and phenotypic data, we propose that strains PB105^T and PB108 represent a novel species of the genus Hymenobacter, for which the name Hymenobacter daejeonensis sp. nov. is proposed. The type strain is PB105^T (= KCTC 52579^T = JCM 31885^T).

Hymenobacter segetis sp. nov., isolated from soil

A polyphasic taxonomic study was performed on a novel strain designated as S7-3-11^T, which was isolated from soil of the Gyeongsangnam-do province in Republic of Korea. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain S7-3-11^T belongs to the genus Hymenobacter and is most closely related to Hymenobacter ruber PB156^T (97.9%), Hymenobacter daeguensis 16F3Y-2^T (97.8%), Hymenobacter glaciei VUG-A130^T (97.7%), Hymenobacter soli PB17^T (97.5%), Hymenobacter terrae DG7A^T (97.5%), and Hymenobacter antarcticus VUG-A42aa^T (97.3%). However, DNA-DNA hybridization results showed less than 50% relatedness with respect to the type strains of the six most closely related species. The DNA G + C content of strain S7-3-11^T was 60.2 mol%. MK-7 was identified as the predominant respiratory quinone, and summed feature 3 (C_16:1 ω7c/C_16:1 ω6c; 21.5%), C_15:0 iso (16.8%), C_15:0 anteiso (16.2%), and C_15:1 iso G (10.8%) were the major fatty acids. Phosphatidylethanolamine, an unidentified aminolipid, and an unidentified aminophospholipid were detected as major polar lipids. On the basis of the polyphasic evidence presented, strain S7-3-11^T is considered to represent a novel species of the genus Hymenobacter, for which the name Hymenobacter segetis sp. nov. is proposed. The type strain is S7-3-11^T (= KCTC 52732^T = JCM 32197^T).

Back to the future in a petri dish: Origin and impact of resurrected microbes in natural populations

Current natural populations face new interactions because of the re-emergence of ancient microbes and viruses. These risks come from the re-emergence of pathogens kept in laboratories or from pathogens that are retained in the permafrost, which become available upon thawing due to climate change. We here focus on the effects of such re-emergence in natural host populations based on evolutionary theory of virulence and long-term studies, which investigate host-pathogen adaptations. Pathogens tend to be locally and temporally adapted to their co-occurring hosts, but when pathogens from a different environment or different time enter the host community, the degree to which a new host-pathogen interaction is a threat will depend on the specific genotypic associations, the time lag between the host and the pathogen, and the interactions with native or recent host and pathogen species. Some insights can be obtained from long-term studies using a resurrection ecology approach. These long-term studies based on time-shift experiments are essential to obtain insight into the mechanisms underlying host-pathogen coevolution at several ecological and temporal scales. As past pathogens and their corresponding host(s) can differ in infectivity and susceptibility, strong reciprocal selective pressures can be induced by the pathogen. These strong selective pressures often result in an escalating arms race, but do not necessarily result in increased infectivity over time. Human health can also be impacted by these resurrected pathogens as the majority of emerging infectious diseases are zoonoses, which are infectious diseases originating from animal populations naturally transmitted to humans. The sanitary risk associated with pathogen emergence from different environments (spatial or temporal) depends on a combination of socioeconomic, environmental, and ecological factors that affect the virulence or the pathogenic potential of microbes and their ability to infect susceptible host populations.

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).

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.

Diversity structure of culturable bacteria isolated from the Fildes Peninsula (King George Island, Antarctica): A phylogenetic analysis perspective

It has been proposed that Antarctic environments select microorganisms with unique biochemical adaptations, based on the tenet 'Everything is everywhere, but, the environment selects' by Baas-Becking. However, this is a hypothesis that has not been extensively evaluated. This study evaluated the fundamental prediction contained in this hypothesis-in the sense that species are structured in the landscape according to their local habitats-, using as study model the phylogenetic diversity of the culturable bacteria of Fildes Peninsula (King George Island, Antarctica). Eighty bacterial strains isolated from 10 different locations in the area, were recovered. Based on phylogenetic analysis of 16S rRNA gene sequences, the isolates were grouped into twenty-six phylotypes distributed in three main clades, of which only six are exclusive to Antarctica. Results showed that phylotypes do not group significantly by habitat type; however, local habitat types had phylogenetic signal, which support the phylogenetic niche conservatism hypothesis and not a selective role of the environment like the Baas-Becking hypothesis suggests. We propose that, more than habitat selection resulting in new local adaptations and diversity, local historical colonization and species sorting (i.e. differences in speciation and extinction rates that arise by interaction of species level traits with the environment) play a fundamental role on the culturable bacterial diversity in Antarctica.

Hymenobacter aquaticus sp. nov., a radiation-resistant bacterium isolated from a river

A Gram-stain-negative, non-motile, non-spore-forming, rod-shaped, aerobic bacterial strain, designated 16F3PT, was isolated from the Han River, South Korea, and characterized taxonomically using a polyphasic approach. Phylogenetic analysis based on 16S rRNA gene sequences revealed 16F3PT to be within the genus Hymenobacter, and most closely related to Hymenobacterchitinivorans Txc1T (98.62 %) and Hymenobacterelongatus VUG-A112T (98.46 %). The phylogenetic distance from other species of the genus Hymenobacter with validly published names was greater than 4 % (i.e. sequence similarity was less than 96.0 %). Chemotaxonomic data also supported the classification of strain 16F3PT within the genus Hymenobacter. C16 : 0 (19.8 %), summed feature 3 (C16 : 1ω7c/C16 : 1ω6c; 15.4 %) and iso-C15 : 0 (13.0 %) were the major fatty acids, MK-7 was the predominant respiratory quinone, and phosphatidylethanolamine was the major polar lipid. The G+C content of the genomic DNA of strain 16F3PT was 61.9 mol%. DNA-DNA hybridization experiments showed that the values for DNA-DNA relatedness between strain 16F3PT and the phylogenetically closest neighbours were below 19 %. On the basis of its phenotypic properties and phylogenetic distinctiveness, strain 16F3PT represents a novel species of the genus Hymenobacter, for which the name Hymenobacter aquaticus sp. nov. is proposed. The type strain is 16F3PT (=KCTC 52194T=JCM 31653T).

Arcticibacterium luteifluviistationis gen. nov., sp. nov., isolated from Arctic seawater

A Gram-staining-negative, aerobic, non-motile and yellow-pigmented bacterium, designated strain SM1504T, was isolated from Arctic seawater. It hydrolysed aesculin and gelatin but did not reduce nitrate to nitrite. Phylogenetic analysis of 16S rRNA gene sequences revealed that strain SM1504T constituted a distinct phylogenetic line within the family Cytophagaceae and was closely related to species of the genera Lacihabitans, Emticicia, Fluviimonas and Leadbetterella, with respect to which low sequence similarities between 88.9 and 91.6 % were observed. The major fatty acids of strain SM1504T were summed feature 3 (comprising C16 : 1ω7c and/or iso-C15 : 0 2-OH) and iso-C15 : 0. The predominant polar lipids of strain SM1504T were phosphatidylethanolamine and one unidentified lipid. The only respiratory quinone detected in strain SM1504T was MK7. The DNA G+C content of strain SM1504T was 40.8 mol%. On the basis of the phylogenetic, chemotaxonomic and phenotypic characterization in this study, strain SM1504T is considered to represent a novel species in a new genus of the family Cytophagaceae, for which the name Arcticibacterium luteifluviistationis gen. nov., sp. nov. is proposed. The type strain is SM1504T (=KCTC 42716T=CCTCC AB 2015348T).

Hymenobacter knuensis sp. nov., Isolated From River Water

A Gram-stain-negative, non-motile, non-spore-forming, rod-shaped, aerobic bacterial strain, designated 16F7C-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 16F7C-2^T belonged to the family Cytophagaceae in the phylum Bacteroidetes and was most closely related to Hymenobacter algoricola VUG-A23a^T (98.3%) and Hymenobacter fastidiosus VUG-A124^T (97.7%). The G + C content of the genomic DNA of strain 16F7C-2^T was 63.4 mol%. The detection of menaquinone MK-7 as the predominant respiratory quinone; a fatty acid profile with summed feature 3 (C_16:1 ω7c/C_16:1 ω6c; 19.5%), summed feature 4 (C_17:1 iso I/C_17:1 anteiso B; 15.9%), C_15:0 iso (12.6%), C_16:1 ω5c (10.5%), and C_15:0 anteiso (10.4%) as the major components; and a polar lipid profile with phosphatidylethanolamine as the major component also supported the affiliation of strain 16F7C-2^T to the genus Hymenobacter. The DNA-DNA relatedness between strain 16F7C-2^T and H. algoricola JCM 17214^T and H. fastidiosus JCM17224^T were 45.2 ± 5.8 and 40.3 ± 2.9%, respectively, clearly showing that the isolate constitutes a new genospecies. Strain 16F7C-2^T could be clearly differentiated from its closest neighbors on the basis of its phenotypic, genotypic, and chemotaxonomic features. Therefore, strain 16F7C-2^T represents a novel species of the genus Hymenobacter, for which the name Hymenobacter knuensis sp. nov. is proposed. The type strain is 16F7C-2^T (=KCTC 52538^T = JCM 31814^T).