Polaribacter gen. nov., with three new species, P. irgensii sp. nov., P. franzmannii sp. nov. and P. filamentus sp. nov., gas vacuolate polar marine bacteria of the Cytophaga-Flavobacterium-Bacteroides group and reclassification of 'Flectobacillus glomeratus' as Polaribacter glomeratus comb. nov

Polaribacter uvawellassae sp. nov., a Member of the Family Flavobacteriaceae Isolated from Mud Crab (Scylla serrata)

A Gram-stain-negative, strictly aerobic, rod-shaped, and no flagella, designated SLMDC-22 T, was isolated from the intestine of a mud crab (Scylla serrata). The molecular phylogenetic analysis based on 16S rRNA gene sequences indicated that strain SLMDC-22 T belonged to the genus Polaribacter and exhibited 96.9% similarity to P. huanghezhanensis, 96.5% to P. pacificus, 95.8% to P. lacunae, and 94.1% to P. marinivivus. The G + C content of the DNA of strain SLMDC-22 T was 30.3%. Growth occurred at 4-34 °C (optimum, 23 °C), at pH 5-9 (optimum, pH 7.0), and with 0.5-2.0% (w/v) NaCl (optimum, 2%). The major fatty acid was iso-C15:0. Major polar lipids include phospholipid, phosphatidylmonomethylethanolamine, phosphatidylethanolamine, amino lipid, glycolipid, amino phospholipid, and an unknown polar lipid. The major respiratory quinone is MK-6. Based on whole-genome analysis, the orthologous average nucleotide identity (ANI) with the two closest relatives, Polaribacter huanghezhanensis and Polaribacter pacificus, were 87.3% and 75.7%, respectively. Furthermore, the digital DNA-DNA hybridization (dDDH) values against Polaribacter huanghezhanensis and Polaribacter pacificus were 75.8% and 19.6%, respectively. Notably, 25 genes of SLMDC-22 T were associated with nitrogen metabolism, including denitrification, nitrate ammonification, ammonium assimilation, and nitrosative stress. The phenotypic, genotypic, phylogenetic, and chemotaxonomic data revealed that strain SLMDC-22 T represents a novel species of the genus Polaribacter, for which the name Polaribacter uvawellassae sp. nov. is proposed. The type strain is SLMDC-22 T (= KCTC 102289 T = MCCC 1K09222T).

Thalassobellus suaedae gen. nov., sp. nov., a marine bacterium of the family Flavobacteriaceae isolated from a halophyte Suaeda japonica

Two Gram-stain-negative, facultative anaerobic, rod-shaped and non-gliding bacteria, designated as HL-DH10T and HL-DH14, were isolated from the halophyte Suaeda japonica in a mudflat, Republic of Korea. Based on the results of 16S rRNA gene pairwise analysis, the two isolates were the members of the family Flavobacteriaceae, and Aestuariibaculum suncheonense SC17T was the most closely related to strains HL-DH10T and HL-DH14 with 96.3% and 95.4% sequence similarity, respectively. The average nt identity and digital DNA-DNA hybridization values between strains HL-DH10T and HL-DH14 and other related species were all less than 79.2% and 21.9%, respectively. The genomic DNA G+C contents of strains HL-DH10T and HL-DH14 were 32.0% and 31.5%, respectively. Cells of these strains showed optimal growth at 25 °C, pH 6.5-7.0 and 2.5-4.0% (w/v) sea salts. The major respiratory quinone was menaquinone-6. The major cellular fatty acids were iso-C15:0 (14.0-16.0%), iso-C15:1 G (10.0-12.0%), iso-C17:0 3-OH (12.4-13.9%), iso-C15:0 3-OH (11.8-14.9%) and anteiso-C15:0 (9.4-10.6%). The polar lipids consisted of phosphatidylethanolamine, an unidentified aminophospholipid, two to three unidentified aminolipids and three unidentified lipids. The comprehensive phylogenetic, genomic, phenotypic and chemotaxonomic results indicate that strains HL-DH10T and HL-DH14 are considered to represent a novel genus of Flavobacteriaceae. Hence, we propose the novel genus Thalassobellus suaedae gen. nov., sp. nov. The type strain is HL-DH10T (=KCCM 90512T=JCM 36598T).

Evidence of habitat specificity in sponge microbiomes from Antarctica

BACKGROUND

Marine sponges and their microbiomes are ecosystem engineers distributed across the globe. However, most research has focused on tropical and temperate sponges, while polar regions like Antarctica have been largely neglected. Despite its harsh conditions and geographical isolation, Antarctica is densely populated by sponges. In this study, we explored the extent of habitat specificity in the diversity, community composition, and microbial co-occurrence within Antarctic sponge microbiomes, in comparison to those from other marine environments. We used massive sequencing of 16S rRNA genes and integrated multiple databases to incorporate Antarctic sponges as a habitat in global microbiome analyses.

RESULTS

Our study revealed significant differences in microbial diversity and community composition between Antarctic and non-Antarctic sponges. We found that most microorganisms present in Antarctic sponges are unique to the South Shetland Islands. Nitrosomonas oligotropha, Candidatus Nitrosopumilus, Polaribacter, SAR116 clade, and Low Salinity Nitrite-Oxidizing Bacteria (LS-NOB) are microbial members characterizing the Antarctic sponge microbiomes. Based on their exclusivity and presence across different sponges worldwide, we identified habitat-specific and habitat-generalist bacteria associated with each habitat. They are particularly abundant and connected within all the Antarctic sponges, suggesting that they may play a crucial role as keystone species within these sponge ecosystems.

CONCLUSIONS

This study provides significant insights into the microbial diversity and community composition of sponges in Antarctica and non-Antarctic ecoregions. Our findings provide evidence for habitat-specific patterns that differentiate the microbiomes of Antarctic sponges from elsewhere, indicating the strong influence of environmental selection and dispersal limitation wrapped into the Antarctic ecoregions to shape more similar microbial communities in distantly related sponges. This study contributes to understanding signatures of microbial community assembly in the Antarctic sponges and has important implications for the ecology and evolution of these unique marine environments.

Polaribacter ponticola sp. nov., isolated from seawater, reclassification of Polaribacter undariae as a later heterotypic synonym of Polaribacter sejongensis, and emended description of Polaribacter sejongensis Kim et al. 2013

A Gram-stain-negative, yellow-pigmented, and strictly aerobic bacterium, designated as strain MSW5T, was isolated from seawater of the Yellow Sea in South Korea. The cells were non-motile rods exhibiting oxidase- and catalase-positive activities. Growth was observed at 15-25 °C (optimum, 25 °C) and pH 5.0-9.0 (optimum, pH 7.0-8.0) and in the presence of 1.0-5.0% (w/v) NaCl (optimum, 2.0%). Menaquinone-6 was the sole respiratory quinone, and iso-C15 : 0, summed feature 3 (C16 : 1  ω7c and/or C16 : 1  ω6c), iso-C15 : 0 3-OH, and C15 : 1  ω6c were the major cellular fatty acids. Major polar lipids included phosphatidylethanolamine, two unidentified aminolipids, and three unidentified lipids. Phylogenetic analyses based on 16S rRNA gene sequences and 92 concatenated core protein sequences revealed that strain MSW5T formed a distinct lineage within the genus Polaribacter. The genome of strain MSW5T was 3582 kb in size with a 29.1 mol% G+C content. Strain MSW5T exhibited the highest similarity to Polaribacter atrinae WP25T, with a 97.9% 16S rRNA gene sequence similarity. However, the average nucleotide identity and digital DNA-DNA hybridization values were 79.4 and 23.3%, respectively, indicating that strain MSW5T represents a novel species. Based on its phenotypic, chemotaxonomic, and phylogenetic characteristics, strain MSW5T is proposed to represent a novel species, with the name Polaribacter ponticola sp. nov. The type strain is MSW5T (=KACC 22340T=NBRC 116025T). In addition, whole genome sequence comparisons and phenotypic features suggested that Polaribacter sejongensis and Polaribacter undariae belong to the same species, with P. undariae proposed as a later heterotypic synonym of P. sejongensis. An emended description of Polaribacter sejongensis is also proposed.

Microbiome profile of the Antarctic clam Laternula elliptica

The filter feeder clam Laternula elliptica is a key species in the Antarctic ecosystem. As a stenothermal benthic species, it has a poor capacity for adaptation to small temperature variations. Despite their ecological importance and sensitivity to climate change, studies on their microbiomes are lacking. The goal of this study was to characterize the bacterial communities of L. elliptica and the tissues variability of this microbiome to provide an initial insight of host-microbiota interactions. We investigated the diversity and taxonomic composition of bacterial communities of L. elliptica from five regions of the body using high-throughput 16S rRNA gene sequencing. The results showed that the microbiome of L. elliptica tended to differ from that of the surrounding seawater samples. However, there were no significant differences in the microbial composition between the body sites, and only two OTUs were present in all samples, being considered core microbiome (genus Moritella and Polaribacter). No significant differences were detected in diversity indexes among tissues (mean 626.85 for observed OTUs, 628.89 Chao1, 5.42 Shannon, and 0.87 Simpson). Rarefaction analysis revealed that most tissues reached a plateau of OTU number according to sample increase, with the exception of Siphon samples. Psychromonas and Psychrilyobacter were particularly abundant in L. elliptica whereas Fluviicola dominated seawater and siphons. Typical polar bacteria were Polaribacter, Shewanella, Colwellia, and Moritella. We detected the prevalence of pathogenic bacterial sequences, particularly in the family Arcobacteraceae, Pseudomonadaceae, and Mycoplasmataceae. The prokaryotic diversity was similar among tissues, as well as their taxonomic composition, suggesting a homogeneity of the microbiome along L. elliptica body. The Antarctic clam population can be used to monitor the impact of human activity in areas near Antarctic stations that discharge wastewater.

Complete genome of Polaribacter huanghezhanensis KCTC 32516T isolated from glaciomarine fjord sediment of Svalbard

Polaribacter huanghezhanensis KCTC 32516T is an aerobic, non-flagellated, Gram-negative, orange-colony-forming bacterium that was isolated from the surficial glaciomarine sediment of inner basin of Kongsfjorden, Svalbard. The sampling site is characterized by a sedimentation of organic depleted lithogenous particles from the nearby glaciers, resulting in reduction of organic matter concentration. In order to understand microbial adaptation to the oligotrophic environment, we here sequenced the complete genome of the P. huanghezhanensis KCTC 32516T. The genome consists of 2,587,874 bp (G + C content of 31.5%) with a single chromosome, 2391 protein-coding genes, 39 tRNAs, and 2 rRNA operons. Our comparative analysis revealed that the P. huanghezhanensis possess the smallest genome in fifteen Polaribacter species with genome. The streamlined genome of this species, required less resource in replication, could evolved by the nutrient deficiency in surrounding environment. Simultaneously, the 15 KOs involved in amino acid biosynthesis and anaplerotic carbon fixation is uniquely absent in the P. huanghezhanensis. In addition, although the advantage of small genome, other 15 KOs involved in resource recycling and stress resistance is uniquely present in sequenced genome. This result demonstrates that the sequenced genome serves as a valuable model for further studies aimed at elucidating the molecular mechanisms associated with adaptation to oligotrophic habitat.

Jiella pelagia sp. nov., isolated from the phosphonate-amended seawater of the northwestern Pacific Ocean

A novel Gram-stain-negative, aerobic, rod-shaped bacterium, designated as HL-NP1T, was isolated from the surface water of the northwestern Pacific Ocean after enrichment cultivation using the organic phosphorous compound of 2-aminoethylphosphonate. Phylogenetic analysis based on 16S rRNA gene sequences showed that the strain belonged to the genus Jiella, with the highest similarity to Jiella pacifica 40Bstr34T (98.7 %). The complete genome sequence of strain HL-NP1T comprised a circular chromosome of 5.58 Mbp and two circular plasmids of 0.15 and 0.22 Mbp. Comparison of the genome sequences between strains HL-NP1T and J. pacifica 40Bstr34T revealed that average nucleotide identity, average amino acid identity and digital DNA-DNA hybridization values (88.0, 86.4 and 33.9 %, respectively) were below the recommended cut-off levels for delineating bacterial species. Strain HL-NP1T showed optimal growth at 30 °C, pH 6.5-7.0, with 2.0-2.5 % (w/v) NaCl. The sole respiratory quinone was ubiquinone-10. The predominant fatty acid was summed feature 8 (C18 : 1  ω6c and/or C18 : 1  ω7c). The polar lipids comprised diphosphatidylglycerol, phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, phosphatidylmonomethylethanolamine, an unidentified aminolipid and four unidentified lipids. The G+C content of the genomic DNA was 65.1 %. Based on phylogenetic, genotypic, phenotypic and chemotaxonomic data, strain HL-NP1T is proposed to represent a novel species of the genus Jiella, for which the name Jiella pelagia sp. nov. is proposed. The type strain is HL-NP1T (= KCCM 90499T = JCM 35838T).

Colwellia maritima sp. nov. and Polaribacter marinus sp. nov., isolated from seawater

Two Gram-stain-negative, catalase- and oxidase-positive, and aerobic bacteria, strains MSW7^T and MSW13^T, were isolated from seawater. Cells of strains MSW7^T and MSW13^T are motile and non-motile rods, respectively. Strain MSW7^T optimally grew at 25 °C and pH 7.0 and in the presence of 3 % (w/v) NaCl, whereas strain MSW13^T optimally grew at 25 °C and pH 6.0-7.0 and in the presence of 2 % NaCl. As the sole respiratory quinone and the major fatty acids and polar lipids, strain MSW7^T contained ubiquinone-8, C_16 : 0, C_15 : 1  ω8c, C_17 : 1  ω8c and summed feature 3 (C_16 : 1  ω7c and/or C_16 : 1  ω6c), and phosphatidylethanolamine and phosphatidylglycerol, respectively, whereas strain MSW13^T contained menaquinone-6, C_15 : 1  ω6c, iso-C_15 : 0, anteiso-C_15 : 0, and iso-C_15 : 0 3-OH, and phosphatidylethanolamine, respectively. The DNA G+C contents of strains MSW7^T and MSW13^T were 37.3 and 29.9 %, respectively. Phylogenetic analyses based on 16S rRNA gene sequences showed that strains MSW7^T and MSW13^T were most closely related to Colwellia echini A3^T and Polaribacter atrinae WP25^T with 98.8 and 98.1 % sequence similarities, respectively. The average nucleotide identity and digital DNA-DNA hybridization values between strain MSW7^T and C. echini A3^T and between strain MSW13^T and P. atrinae KACC 17473^T were 73.6 and 22.6 % and 80.4 and 23.8 %, respectively. Based on phenotypic, chemotaxonomic and phylogenetic data, strains MSW7^T and MSW13^T represent novel species of the genera Colwellia and Polaribacter, respectively, for which the names Colwellia maritima sp. nov. and Polaribacter marinus sp. nov. are proposed, respectively. The type strains of C. maritima sp. nov. and P. marinus sp. nov. are MSW7^T (=KACC 22339^T=JCM 35001^T) and MSW13^T (=KACC 22341^T=JCM 35021^T), respectively.

Microbial Communities in Volcanic Glacier Ecosystems

Glaciers constitute a polyextremophilic environment characterized by low temperatures, high solar radiation, a lack of nutrients, and low water availability. However, glaciers located in volcanic regions have special characteristics, since the volcanic foci provide them with heat and nutrients that allow the growth of microbial communities highly adapted to this environment. Most of the studies on these glacial ecosystems have been carried out in volcanic environments in the northern hemisphere, including Iceland and the Pacific Northwest. To better know, the microbial diversity of the underexplored glacial ecosystems and to check what their specific characteristics were, we studied the structure of bacterial communities living in volcanic glaciers in Deception Island, Antarctica, and in the Kamchatka peninsula. In addition to geographic coordinates, many other glacier environmental factors (like volcanic activity, altitude, temperature, pH, or ice chemical composition) that can influence the diversity and distribution of microbial communities were considered in this study. Finally, using their taxonomic assignments, an attempt was made to compare how different or similar are the biogeochemical cycles in which these microbiomes are involved.

Stability of the Microbiome of the Sponge Mycale (Oxymycale) acerata in the Western Antarctic Peninsula

The sponge microbiome, especially in Low Microbial Abundance (LMA) species, is expected to be influenced by the local environment; however, contrasting results exist with evidence showing that host specificity is also important, hence suggesting that the microbiome is influenced by host-specific and environmental factors. Despite sponges being important members of Southern Ocean benthic communities, their relationships with the microbial communities they host remain poorly studied. Here, we studied the spatial and temporal patterns of the microbiota associated with the ecologically important LMA sponge M. acerata at sites along ∼400 km of the Western Antarctic Peninsula (WAP) to assess patterns in the core and variable microbial components of the symbiont communities of this sponge species. The analyses of 31 samples revealed that the microbiome of M. acerata is composed of 35 prokaryotic phyla (3 Archaea, 31 Bacteria, and one unaffiliated), being mainly dominated by Proteobacteria with Gammaproteobacteria as the most dominant class. The core community was composed of six prokaryotic OTUs, with gammaproteobacterial OTU (EC94 Family), showing a mean abundance over 65% of the total abundance. Despite some differences in rare OTUs, the core community did not show clear patterns in diversity and abundance associated with specific sites/environmental conditions, confirming a low variability in community structure of this species along the WAP. The analysis at small scale (Doumer Island, Palmer Archipelago) showed no differences in space and time in the microbiome M. acerata collected at sites around the island, sampled in three consecutive years (2016-2018). Our results highlight the existence of a low spatial and temporal variability in the microbiome of M. acerata, supporting previous suggestions based on limited studies on this and other Antarctic sponges.

Szabonella alba gen. nov., sp. nov., a motile alkaliphilic bacterium of the family Rhodobacteraceae isolated from a soda lake

A Gram-stain-negative, oxidase- and catalase-positive, rod-shaped, creamy white coloured bacterial strain, DMG-N-6T, was isolated from a water sample of Lake Fertő/Neusiedler See (Hungary). Phylogenetic analysis based on 16S rRNA gene sequences revealed that the strain forms a distinct linage within the family Rhodobacteraceae . Its closest relatives are Tabrizicola alkalilacus DJCT (96.76% similarity) and Tabrizicola piscis K13M18T (96.76%), followed by Tabrizicola sediminis DRYC-M-16T (96.69 %), Rhodobacter sediminicola JA983T (96.62 %), Tabrizicola aquatica RCRI19T (96.47 %) and Cereibacter johrii JA192T (96.18 %). The novel bacterial strain favours an alkaline environment (pH 8.0-12.0) and grows optimally at 18–28°C in the presence of 2–4 % (w/v) NaCl. Cells of DMG-N-6T were motile by a single subpolar flagellum. Bacteriochlorophyll a was not detected. The predominant respiratory quinone was ubiquinone Q-10. The major cellular fatty acid was C18:1 ω7c. The polar lipid profile comprised phosphatidylglycerol, diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylserine, phosphatidylcholine, an unidentified phospholipid and five unidentified lipids. The assembled draft genome of strain DMG-N-6T had 52 contigs with a total length of 4 219 778 bp and a G+C content of 64.3 mol%. Overall genome-related indices (ANI <77.8 %, AAI <69.0 %, dDDH <19.6 %) with respect to close relatives were all significantly below the corresponding threshold to demarcate bacterial genus and species. Strain DMG-N-6T (=DSM 108208T=NCAIM B.02645T) is strongly different from its closest relatives and is suggested as the type strain of a novel species of a new genus in the family Rhodobacteraceae , for which the name Szabonella alba gen. nov., sp. nov. is proposed.

Bacterioplankton Diversity and Distribution in Relation to Phytoplankton Community Structure in the Ross Sea Surface Waters

Primary productivity in the Ross Sea region is characterized by intense phytoplankton blooms whose temporal and spatial distribution are driven by changes in environmental conditions as well as interactions with the bacterioplankton community. However, the number of studies reporting the simultaneous diversity of the phytoplankton and bacterioplankton in Antarctic waters are limited. Here, we report data on the bacterial diversity in relation to phytoplankton community structure in the surface waters of the Ross Sea during the Austral summer 2017. Our results show partially overlapping bacterioplankton communities between the stations located in the Terra Nova Bay (TNB) coastal waters and the Ross Sea Open Waters (RSOWs), with a dominance of members belonging to the bacterial phyla Bacteroidetes and Proteobacteria. In the TNB coastal area, microbial communities were characterized by a higher abundance of sequences related to heterotrophic bacterial genera such as Polaribacter spp., together with higher phytoplankton biomass and higher relative abundance of diatoms. On the contrary, the phytoplankton biomass in the RSOW were lower, with relatively higher contribution of haptophytes and a higher abundance of sequences related to oligotrophic and mixothrophic bacterial groups like the Oligotrophic Marine Gammaproteobacteria (OMG) group and SAR11. We show that the rate of diversity change between the two locations is influenced by both abiotic (salinity and the nitrogen to phosphorus ratio) and biotic (phytoplankton community structure) factors. Our data provide new insight into the coexistence of the bacterioplankton and phytoplankton in Antarctic waters, suggesting that specific rather than random interaction contribute to the organic matter cycling in the Southern Ocean.

Seasonal and annual changes in the microbial communities of Ofunato Bay, Japan, based on metagenomics

Five years of datasets from 2015 to 2019 of whole genome shotgun sequencing for cells trapped on 0.2-µm filters of seawater collected monthly from Ofunato Bay, an enclosed bay in Japan, were analysed, which included the 2015 data that we had reported previously. Nucleotide sequences were determined for extracted DNA from three locations for both the upper (1 m) and deeper (8 or 10 m) depths. The biotic communities analysed at the domain level comprised bacteria, eukaryotes, archaea and viruses. The relative abundance of bacteria was over 60% in most months for the five years. The relative abundance of the SAR86 cluster was highest in the bacterial group, followed by Candidatus Pelagibacter and Planktomarina. The relative abundance of Ca. Pelagibacter showed no relationship with environmental factors, and those of SAR86 and Planktomarina showed positive correlations with salinity and dissolved oxygen, respectively. The bacterial community diversity showed seasonal changes, with high diversity around September and low diversity around January for all five years. Nonmetric multidimensional scaling analysis also revealed that the bacterial communities in the bay were grouped in a season-dependent manner and linked with environmental variables such as seawater temperature, salinity and dissolved oxygen.

The bank of swimming organisms at the micron scale (BOSO-Micro)

Unicellular microscopic organisms living in aqueous environments outnumber all other creatures on Earth. A large proportion of them are able to self-propel in fluids with a vast diversity of swimming gaits and motility patterns. In this paper we present a biophysical survey of the available experimental data produced to date on the characteristics of motile behaviour in unicellular microswimmers. We assemble from the available literature empirical data on the motility of four broad categories of organisms: bacteria (and archaea), flagellated eukaryotes, spermatozoa and ciliates. Whenever possible, we gather the following biological, morphological, kinematic and dynamical parameters: species, geometry and size of the organisms, swimming speeds, actuation frequencies, actuation amplitudes, number of flagella and properties of the surrounding fluid. We then organise the data using the established fluid mechanics principles for propulsion at low Reynolds number. Specifically, we use theoretical biophysical models for the locomotion of cells within the same taxonomic groups of organisms as a means of rationalising the raw material we have assembled, while demonstrating the variability for organisms of different species within the same group. The material gathered in our work is an attempt to summarise the available experimental data in the field, providing a convenient and practical reference point for future studies.

Airborne bacterial community diversity, source and function along the Antarctic Coast

Antarctica is an isolated and relatively simple ecosystem dominated by microorganisms, providing a rare opportunity to study the spread of airborne microbes and to predict future global climate change. However, little is known about on the diversity and potential sources of microorganisms in the marine atmosphere along the Antarctica coast. Here we explored the airborne bacterial community (i.e., bacteriome) diversity, sources and functional potential along the Antarctic coast based on 16S rRNA gene amplicon sequencing of 25 bioaerosol samples collected during the 33rd Xuelong Antarctic scientific expedition. The results showed that bacterial communities in the Antarctic bioaerosols i) were predominated by Proteobacteria (91.3%) including Sphingomonas, ii) showed relative low alpha-diversity but high spatiotemporal variabilities; and iii) were potentially immigrated with terrestrial, marine and Antarctic polar bacteria through long-range transport and sea-air exchange pathways. Moreover, canonical correspondence analysis of bacteriome composition showed that wind speed, temperature, and organic carbon had a significant effect on the bacterial community (P < 0.05), although bacterial richness (Richness index) and diversity (Simpson index and Shannon index) showed no statistically significant differences between rainy, cloudy and snowy weather conditions (Adjust P > 0.05, ANOVA, Tukey HSD test). iv) The functional profiles predicted by Tax4fun2 suggest high representation of function genes related to fatty acid biosynthesis and metabolism, amino acid metabolism, nucleotide metabolism, and carbohydrate metabolism, which is conducive to the formation of microlayers on the surface of the ocean and the survival and growth of bacteria.

Fertoeibacter niger gen. nov., sp. nov. a novel alkaliphilic bacterium of the family Rhodobacteraceae

Three Gram-stain-negative, non-motile, oxidase- and catalase-positive, rod-shaped, black, facultative phototrophic bacterial strains, RG-N-1a^T, DMA-N-7a and RA-N-9 were isolated from the water sample from Lake Fertő/Neusiedler See (Hungary). Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the strains form a distinct linage within the family Rhodobacteraceae and their closest relatives are Tabrizicola piscis K13M18^T (96.32%) followed by Cypionkella psychrotolerans PAMC 27389^T (96.25%). The novel bacterial strains prefer alkaline environments and grow optimally at 23-33 °C in the presence of NaCl (1-2 w/v%). Bacteriochlorophyll a was detected. Cells contained exclusively ubiquinone Q-10. The major cellular fatty acids were C_{18 : 1}ω7c, C_{19 : 1}iso ω5c, C_{18 : 0} 3-OH and C_{18 : 1}ω7c 11-methyl. The polar lipid profile contains diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, an unidentified phospholipid and four unidentified lipids. The assembled draft genome of RG-N-1a^T had 33 contigs with N50 values 315 027 nt, 96× genome coverage, total length of 4 326 551 bp and a DNA G+C content of 64.9%. Genome-based calculations (genome-to-genome distance and DNA G+C percentage) and pairwise amino acid identity (AAI <73.5%) indicate that RG-N-1a^T represents a novel genus. RG-N-1a^T (=DSM 108317^T=NCAIM B.02647^T) is suggested as the type strain of a novel genus and species in the family Rhodobacteraceae, for which the name Fertoeibacter niger gen. nov., sp. nov. is proposed.

Muricauda sediminis sp. nov., isolated from western Pacific Ocean sediment

A Gram-stain-negative bacterium, designated strain 40Bstr401^T, was isolated from a sediment sample collected from the western Pacific Ocean. Analysis of its 16S rRNA gene sequence revealed that strain 40Bstr401^T belongs to the genus Muricauda and is closely related to type strains Muricauda antarctica Ar-22^T (98.2 %), Muricauda taeanensis 105^T (98.2 %) and Muricauda beolgyonensis BB-My12^T (97.4 %). The average nucleotide identity values for 40Bstr401^T with M. antarctica Ar-22^T and M. taeanensis 105^T are 79.3 % and 78.8 %, respectively. The in silico DNA-DNA hybridization values between strain 40Bstr401^T and M. antarctica Ar-22^T and M. taeanensis 105^T are 26.7 and 26.6 %, respectively. The major isoprenoid quinone of 40Bstr401^T is MK-6, and iso-C_17 : 0 3-OH and iso-C_15 : 0 are the dominant cellular fatty acids. The major polar lipids are phosphatidylethanolamine, four unidentified amino lipids and two unidentified lipids. The G+C content of the genomic DNA is 42.9 mol%. Its phylogenetic distinctiveness and chemotaxonomic differences, together with the phenotypic properties observed in this study, indicate that strain 40Bstr401^T can be differentiated from closely related species. Therefore, we propose strain 40Bstr401^T represents a novel species in the genus Muricauda, for which the name Muricauda sediminis sp. nov. is suggested. The type strain is 40Bstr401^T (=MCCC 1K04568^T=KCTC 82139^T).

Microbial Community Structure Driven by a Volcanic Gradient in Glaciers of the Antarctic Archipelago South Shetland

It has been demonstrated that the englacial ecosystem in volcanic environments is inhabited by active bacteria. To know whether this result could be extrapolated to other Antarctic glaciers and to study the populations of microeukaryotes in addition to those of bacteria, a study was performed using ice samples from eight glaciers in the South Shetland archipelago. The identification of microbial communities of bacteria and microeukaryotes using 16S rRNA and 18S rRNA high throughput sequencing showed a great diversity when compared with microbiomes of other Antarctic glaciers or frozen deserts. Even the composition of the microbial communities identified in the glaciers from the same island was different, which may be due to the isolation of microbial clusters within the ice. A gradient in the abundance and diversity of the microbial communities from the volcano (west to the east) was observed. Additionally, a significant correlation was found between the chemical conditions of the ice samples and the composition of the prokaryotic populations inhabiting them along the volcanic gradient. The bacteria that participate in the sulfur cycle were those that best fit this trend. Furthermore, on the eastern island, a clear influence of human contamination was observed on the glacier microbiome.

Patterns in Benthic Microbial Community Structure Across Environmental Gradients in the Beaufort Sea Shelf and Slope

The paradigm of tight pelagic-benthic coupling in the Arctic suggests that current and future fluctuations in sea ice, primary production, and riverine input resulting from global climate change will have major impacts on benthic ecosystems. To understand how these changes will affect benthic ecosystem function, we must characterize diversity, spatial distribution, and community composition for all faunal components. Bacteria and archaea link the biotic and abiotic realms, playing important roles in organic matter (OM) decomposition, biogeochemical cycling, and contaminant degradation, yet sediment microbial communities have rarely been examined in the North American Arctic. Shifts in microbial community structure and composition occur with shifts in OM inputs and contaminant exposure, with implications for shifts in ecological function. Furthermore, the characterization of benthic microbial communities provides a foundation from which to build focused experimental research. We assessed diversity and community structure of benthic prokaryotes in the upper 1 cm of sediments in the southern Beaufort Sea (United States and Canada), and investigated environmental correlates of prokaryotic community structure over a broad spatial scale (spanning 1,229 km) at depths ranging from 17 to 1,200 m. Based on hierarchical clustering, we identified four prokaryotic assemblages from the 85 samples analyzed. Two were largely delineated by the markedly different environmental conditions in shallow shelf vs. upper continental slope sediments. A third assemblage was mainly comprised of operational taxonomic units (OTUs) shared between the shallow shelf and upper slope assemblages. The fourth assemblage corresponded to sediments receiving heavier OM loading, likely resulting in a shallower anoxic layer. These sites may also harbor microbial mats and/or methane seeps. Substructure within these assemblages generally reflected turnover along a longitudinal gradient, which may be related to the quantity and composition of OM deposited to the seafloor; bathymetry and the Mackenzie River were the two major factors influencing prokaryote distribution on this scale. In a broader geographical context, differences in prokaryotic community structure between the Beaufort Sea and Norwegian Arctic suggest that benthic microbes may reflect regional differences in the hydrography, biogeochemistry, and bathymetry of Arctic shelf systems.

Pseudonocardia cytotoxica sp. nov., a novel actinomycete isolated from an Arctic fjord with potential to produce cytotoxic compound

Herein we report the isolation of a novel actinomycete, strain MCCB 268^T, from the sediment sample collected from a high Arctic fjord Kongsfjorden. MCCB 268^T showed greater than 97% 16S rRNA gene sequence similarity with those of Pseudonocardia konjuensis LM 157^T (98.06%), Pseudonocardia soli NW8-21 (97.22%) Pseudonocardia endophytica YIM 56035 (97.08%) and Pseudonocardia nantongensis KLBMP 1282 (97.34%) showing that the strain should be assigned to the genus Pseudonocardia. DNA-DNA hybridization with Pseudonocardia konjuensis LM 157^T showed only 41.5% relatedness to strain MCCB 268^T. The whole genome of the strain MCCB 268^T was sequenced. Whole-genome average nucleotide identity, dDDH (%) and genome tree analysis demonstrated that strain significantly differed from other Pseudonocardia species. The G + C content was 70.5 mol%. MCCB 268^T exhibited in vitro cytotoxicity and through bioassay guided fractionation followed by HPLC separation a cytotoxic compound (I) was isolated. The compound (I) was identified as 1-acetyl-β-carboline through NMR spectra and high-resolution mass spectrometry. Compound (I) showed cytotoxicity against lung cancer cell line and mode of anticancer activity was found to be through the induction of apoptosis. Based on the genotypic and phenotypic features, MCCB 268^T ought to be classified as a novel species under the genus Pseudonocardia for which the name Pseudonocardia cytotoxica sp. nov. is proposed (= CCUG72333^T = JCM32718^T).

Implications of increasing Atlantic influence for Arctic microbial community structure

Increasing influence of Atlantic water in the Arctic Ocean has the potential to significantly impact regional water temperature and salinity. Here we use a rDNA barcoding approach to reveal how microbial communities are partitioned into distinct assemblages across a gradient of Atlantic-Polar Water influence in the Norwegian Sea. Data suggest that temperate adapted bacteria may replace cold water taxa under a future scenario of increasing Atlantic influence, but the eukaryote response is more complex. Some abundant eukaryotic cold water taxa could persist, while less abundant eukaryotic taxa may be replaced by warmer adapted temperate species. Furthermore, within lineages, different taxa display evidence of increased relative abundance in reaction to favourable conditions and we observed that rare microbial taxa are sample site rather than region specific. Our findings have significant implications for the vulnerability of polar associated community assemblages, which may change, impacting the ecosystem services they provide, under predicted increases of Atlantic mixing and warming within the Arctic region.

Rufibacter radiotolerans sp. nov., a novel gamma-radiation-resistant bacterium isolated from rice field

A red-pigmented isolate, designated DG31D^T, was isolated from the soil of a rice field in South Korea. Cells were strictly aerobic, short rod-shaped, Gram-negative, oxidase-positive, and catalase-positive. The major polar lipid was phosphatidylethanolamine (PE), and the predominant respiratory quinone was MK-7. DG31D^T showed high resistance to both the UV and gamma radiations. Based on the 16S rRNA gene sequence, strain DG31D^T was related to Rufibacter immobilis MCC P1^T (97.1%) and Rufibacter tibetensis 1351^T (96.5%). The average nucleotide identity (ANI) and in silico DNA-DNA hybridization (isDDH) values between the strain DG31D^T and the related Rufibacter sp. were between 74.1-77.6% and 19.9-21.9%, respectively. Strain DG31D^T grew between 15 and 30 °C (optimum, 25 °C), at pH 6.0-8.0 (optimum, pH 7.0) and tolerated up to 1.0% NaCl (w/v). The major cellular fatty acids of the novel strain were summed feature 3 (C_16:1 ω7c/C_16:1 ω6c) and C_16:1 ω5c. Flexirubin-type pigments were absent. On the basis of the phenotypic, phylogenetic, and chemotaxonomic data, strain DG31D^T represents a novel species of the genus Rufibacter, for which the name Rufibacter radiotolerans sp. nov. is proposed. The type strain is DG31D^T (= JCM 19446^T = KCTC 32454^T).

Jiella pacifica sp. nov., isolated from the West Pacific Ocean

A Gram-stain-negative bacterium, designated strain 40Bstr34^T, isolated from a sediment sample from the West Pacific Ocean, was taxonomically characterized by using a polyphasic approach. The strain was phylogenetically close to Jiella aquimaris LZB041^T and Jiella endophytica CBS5Q-3^T, with 16S rRNA gene sequence similarities of 98.5 and 97.1 %, respectively. The genome of strain 40Bstr34^T featured a G+C content of 65.7 % for a 5.8 Mb chromosome. Up-to-date bacterial core gene set analysis revealed that strain 40Bstr34^T represents one independent lineage with J.aquimaris LZB041^T. In silico DNA-DNA hybridization values between strain 40Bstr34^T and its phylogenetic neighbours ranged from 30.3-34.2 %, below the cutoff of 70 %. In addition, the corresponding average nucleotide identity values were between 81.8-83.7 %, which are lower than 95 % threshold. The predominant cellular fatty acids of strain 40Bstr34^T were summed feature 8 (C_18 : 1  ω6c and/or C_18 : 1  ω7c), cyclo-C_19 : 0  ω8c and iso-C_17 : 0 3-OH, and ubiquinone-10 as the predominant respiratory quinone. The major polar lipids included phosphatidylethanolamine, phosphatidylmonomethylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, two unidentified aminolipids and two unidentified lipids. Based on the results of phenotypic, chemotaxonomic and genetic analyses, strain 40Bstr34^T is identified as representing a novel species of the genus Jiella for which the name Jiella pacifica sp. nov. is proposed. The type strain is 40Bstr34^T (=JCM 33903^T=MCCC 1K04569^T).

Polaribacter septentrionalilitoris sp. nov., isolated from the biofilm of a stone from the North Sea

A new member of the family Flavobacteriaceae was isolated from the biofilm of a stone at Nordstrand, a peninsula at the German North Sea shore. Phylogenetic analysis of the 16S rRNA gene sequence showed that strain ANORD1^T was most closely related to the validly described type strains Polaribacter porphyrae LNM-20^T (97.0 %) and Polaribacter reichenbachii KMM 6386^T (96.9 % 16S rRNA gene sequence similarity) and clustered with Polaribacter gangjinensis K17-16^T (96.0 %). Strain ANORD1^T was determined to be mesophilic, Gram-negative, non-motile and strictly aerobic. Optimal growth was observed at 20-30 °C, within a salinity range of 2-7 % sea salt and from pH 7-10. Like other type strains of the genus Polaribacter, ANORD1^T was tested negative for flexirubin-type pigments, while carotenoid-type pigments were detected. The DNA G+C content of strain ANORD1^T was 30.6 mol%. The sole respiratory quinone detected was menaquinone 6 (MK-6). The major fatty acids identified were C_15 : 0, iso-C_15 : 0, C_15 : 1 ω6c and iso-C_15 : 0 3-OH. Based on the polyphasic approach, strain ANORD1^T represents a novel species in the genus Polaribacter, with the name Polaribacter septentrionalilitoris sp. nov. being proposed. The type strain is ANORD1^T (=DSM 110039^T=NCIMB 15081^T=MTCC 12685^T).

Liquid biopsies for omics-based analysis in sentinel mussels

Liquid biopsy of plasma is a simple and non-invasive technology that holds great promise in biomedical research. It is based on the analysis of nucleic acid-based biomarkers with predictive potential. In the present work, we have combined this concept with the FTA technology for sentinel mussels. We found that hemocytes collected from liquid biopsies can be readily fixed on FTA cards and used for long-term transcriptome analysis. We also showed that liquid biopsy is easily adaptable for metagenomic analysis of bacterial profiles of mussels. We finally provide evidence that liquid biopsies contained circulating cell-free DNA (ccfDNA) which can be used as an easily accessible genomic reservoir. Sampling of FTA-fixed circulating nucleic acids is stable at room temperature and does not necessitate a cold-chain protection. It showed comparable performance to frozen samples and is ideally adapted for sampling in remote areas, most notably in polar regions threatened by anthropogenic activities. From an ethical point of view, this minimally-invasive and non-lethal approach further reduces incidental mortality associated with conventional tissue sampling. This liquid biopsy-based approach should thus facilitate biobanking activities and development of omics-based biomarkers in mussels to assess the quality of aquatic ecosystems.

Analysis of 1,000 Type-Strain Genomes Improves Taxonomic Classification of Bacteroidetes

Although considerable progress has been made in recent years regarding the classification of bacteria assigned to the phylum Bacteroidetes, there remains a need to further clarify taxonomic relationships within a diverse assemblage that includes organisms of clinical, piscicultural, and ecological importance. Bacteroidetes classification has proved to be difficult, not least when taxonomic decisions rested heavily on interpretation of poorly resolved 16S rRNA gene trees and a limited number of phenotypic features. Here, draft genome sequences of a greatly enlarged collection of genomes of more than 1,000 Bacteroidetes and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa proposed long ago such as Bacteroides, Cytophaga, and Flavobacterium but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which can be considered valuable taxonomic markers. We detected many incongruities when comparing the results of the present study with existing classifications, which appear to be caused by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. The few significant incongruities found between 16S rRNA gene and whole genome trees underline the pitfalls inherent in phylogenies based upon single gene sequences and the impediment in using ordinary bootstrapping in phylogenomic studies, particularly when combined with too narrow gene selections. While a significant degree of phylogenetic conservation was detected in all phenotypic characters investigated, the overall fit to the tree varied considerably, which is one of the probable causes of misclassifications in the past, much like the use of plesiomorphic character states as diagnostic features.

Diversity and Composition of Pelagic Prokaryotic and Protist Communities in a Thin Arctic Sea-Ice Regime

One of the most prominent manifestations of climate change is the changing Arctic sea-ice regime with a reduction in the summer sea-ice extent and a shift from thicker, perennial multiyear ice towards thinner, first-year ice. These changes in the physical environment are likely to impact microbial communities, a key component of Arctic marine food webs and biogeochemical cycles. During the Norwegian young sea ICE expedition (N-ICE2015) north of Svalbard, seawater samples were collected at the surface (5 m), subsurface (20 or 50 m), and mesopelagic (250 m) depths on 9 March, 27 April, and 16 June 2015. In addition, several physical and biogeochemical data were recorded to contextualize the collected microbial communities. Through the massively parallel sequencing of the small subunit ribosomal RNA amplicon and metagenomic data, this work allows studying the Arctic's microbial community structure during the late winter to early summer transition. Results showed that, at compositional level, Alpha- (30.7%) and Gammaproteobacteria (28.6%) are the most frequent taxa across the prokaryotic N-ICE2015 collection, and also the most phylogenetically diverse. Winter to early summer trends were quite evident since there was a high relative abundance of thaumarchaeotes in the under-ice water column in late winter while this group was nearly absent during early summer. Moreover, the emergence of Flavobacteria and the SAR92 clade in early summer might be associated with the degradation of a spring bloom of Phaeocystis. High relative abundance of hydrocarbonoclastic bacteria, particularly Alcanivorax (54.3%) and Marinobacter (6.3%), was also found. Richness showed different patterns along the depth gradient for prokaryotic (highest at mesopelagic depth) and protistan communities (higher at subsurface depths). The microbial N-ICE2015 collection analyzed in the present study provides comprehensive new knowledge about the pelagic microbiota below drifting Arctic sea-ice. The higher microbial diversity found in late winter/early spring communities reinforces the need to continue with further studies to properly characterize the winter microbial communities under the pack-ice.

Description of Polaribacter aestuariivivens sp. nov., isolated from a tidal flat

A bacterial strain, DBTF-3T, was isolated from a tidal flat of Republic of Korea. Phylogenetic trees of 16S rRNA gene sequences showed that strain DBTF-3T belonged to the genus Polaribacter. Strain DBTF-3T exhibited 16S rRNA gene sequence similarities of 97.1-98.1% to type strains of P. dokdonensis, P. haliotis, P. marinaquae, P. insulae, P. vadi, P. glomeratus, P. irgensii and P. reichenbachii, and 94.0-96.9% to those of the other Polaribacter species. DNA-DNA relatedness values of strain DBTF-3T with type strains of P. marinaquae and P. insulae were 14-19%. Average nucleotide identity and digital DNA-DNA hybridization values between strain DBTF-3T and type strains of six other Polaribacter species were 76.5-83.5% and 20.9-27.1%, respectively. Strain DBTF-3T contained MK-6 as the predominant menaquinone, and iso-C15:0, summed feature 3, iso-C15:1 G and iso-C15:0 3-OH as the major fatty acids. The major polar lipids were phosphatidylethanolamine and one unidentified lipid. Differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain DBTF-3T is separated from Polaribacter species. On the basis of the data presented, strain DBTF-3T (= KACC 19612T = NBRC 113191T) represents a novel species of the genus Polaribacter, for which the name Polaribacter aestuariivivens sp. nov. is proposed.

Arundinibacter roseus gen. nov., sp. nov., a new member of the family Cytophagaceae

Three Gram-stain-negative, aerobic, non-motile, oxidase- and catalase positive, rod-shaped, pink-coloured bacterial strains, DMA-K-7a^T, DMA-K-1 and DMG-N-1, were isolated from water sampled at Lake Fertő/Neusiedler See (Hungary). Phylogenetic analysis based on the 16S rRNA gene sequences revealed that the strains form a distinct linage within the family Cytophagaceae of the phylum Bacteroidetes, and their closest relatives are Rhabdobacter roseus R49^T (95.66 %) and Dyadobacter sediminis Z12^T (95.38 %). The assembled genome of strain DMA-K-7a^T had a total length of 5.8 Mb and a DNA G+C content of 45.7 mol%. The major isoprenoid quinone was menaquinone-7 (MK-7). The major cellular fatty acids were C16 : 1 ω7c, iso-C15 : 0, C16 : 1 ω5c, C16 : 0 and iso-C17 : 0 3-OH. The polar lipid profile contained phosphatidylethanolamine, phosphatidylserine, an unknown aminolipid, an unknown glycolipid and five unknown lipids. Flexirubin-type pigments were absent. Strain DMA-K-7a^T (=DSM 106737^T=NCAIM B.02641^T) is proposed as the type strain of a new genus and species in the family Cytophagaceae, for which the name Arundinibacter roseus gen. nov., sp. nov. is proposed.

Genomic and metatranscriptomic analyses of carbon remineralization in an Antarctic polynya

BACKGROUND

Polynyas in the Southern Ocean are regions of intense primary production, mainly by Phaeocystis antarctica. Carbon fixed by phytoplankton in the water column is transferred to higher trophic levels, and finally, to the deep ocean. However, in the Amundsen Sea, most of this organic carbon does not reach the sediment but is degraded in the water column due to high bacterial heterotrophic activity.

RESULTS

We reconstructed 12 key bacterial genomes from different phases of bloom and analyzed the expression of genes involved in organic carbon remineralization. A high correlation of gene expression between the peak and decline phases was observed in an individual genome bin-based pairwise comparison of gene expression. Polaribacter belonging to Bacteroidetes was found to be dominant in the peak phase, and its transcriptional activity was high (48.9% of the total mRNA reads). Two dominant Polaribacter bins had the potential to utilize major polymers in P. antarctica, chrysolaminarin and xylan, with a distinct set of glycosyl hydrolases. In the decline phase, Gammaproteobacteria (Ant4D3, SUP05, and SAR92), with the potential to utilize low molecular weight-dissolved organic matter (LMW-DOM) including compatible solutes, was increased. The versatility of Gammaproteobacteria may contribute to their abundance in organic carbon-rich polynya waters, while the SAR11 clade was found to be predominant in the sea ice-covered oligotrophic ocean. SAR92 clade showed transcriptional activity for utilization of both polysaccharides and LMW-DOM; this may account for their abundance both in the peak and decline phases. Ant4D3 clade was dominant in all phases of the polynya bloom, implicating the crucial roles of this clade in LMW-DOM remineralization in the Antarctic polynyas.

CONCLUSIONS

Genomic reconstruction and in situ gene expression analyses revealed the unique metabolic potential of dominant bacteria of the Antarctic polynya at a finer taxonomic level. The information can be used to predict temporal community succession linked to the availability of substrates derived from the P. antarctica bloom. Global warming has resulted in compositional changes in phytoplankton from P. antarctica to diatoms, and thus, repeated parallel studies in various polynyas are required to predict global warming-related changes in carbon remineralization.

From Ecology to Biotechnology, Study of the Defense Strategies of Algae and Halophytes (from Trapani Saltworks, NW Sicily) with a Focus on Antioxidants and Antimicrobial Properties

This study aimed at the characterization of the antioxidant power of polyphenol extracts (PE) obtained from the algae Cystoseira foeniculacea (CYS) (Phaeophyta) and from the halophyte Halocnemum strobilaceum (HAL), growing in the solar saltworks of western Sicily (Italy), and at the evaluation of their anti-microfouling properties, in order to correlate these activities to defense strategies in extreme environmental conditions. The antioxidant properties were assessed in the PE based on the total antioxidant activity test and the reducing power test; the anti-microfouling properties of the two PE were evaluated by measuring the growth inhibition of marine fish and shellfish pathogen bacteria as well as marine surface fouling bacteria and microalgae exposed to the fractions. Similar polyphenol content (CYS 5.88 ± 0.75 and HAL 6.03 ± 0.25 mg gallic acid equivalents (GAE) g-1 dried weight, DW) and similar reducing power percentage (93.91 ± 4.34 and 90.03 ± 6.19) were recorded for both species, even if they exhibited a different total antioxidant power (measured by the percentage of inhibition of the radical 2,2 diphenyl-1-picrylhydrazyl DPPH), with CYS (79.30) more active than HAL (59.90). Both PE showed anti-microfouling properties, being inhibitors of adhesion and growth of marine fish and shellfish pathogen bacteria (V. aestuarianus, V. carchariae, V. harveyi, P. elyakovii, H. aquamarina) and fouling bacteria (V. natriegens, V. proteolyticus, P. iirgensii, R. litoralis) with minimum inhibitory concentrations comparable to the commercial antifouling products used as a positive control (SEA-NINE™ 211N). Only CYS was a significant inhibitor of the microalgae strains tested, being able to reduce E. gayraliae and C. closterium growth (MIC 10 µg·mL-1) and the adhesion of all three strains tested (E. gayraliae, C. closterium and P. purpureum), suggesting its promise for use as an antifouling (AF) product.

Taxonomic profiles in metagenomic analyses of free-living microbial communities in the Ofunato Bay

The Ofunato Bay in Iwate Prefecture, Japan is a deep coastal bay located at the center of the Sanriku Rias Coast and considered an economically and environmentally important asset. Here, we describe the first whole genome sequencing (WGS) study on the microbial community of the bay, where surface water samples were collected from three stations along its length to cover the entire bay; we preliminarily sequenced a 0.2 μm filter fraction among sequentially size-fractionated samples of 20.0, 5.0, 0.8 and 0.2 μm filters, targeting the free-living fraction only. From the 0.27-0.34 Gb WGS library, 0.9 × 10⁶-1.2 × 10⁶ reads from three sampling stations revealed 29 bacterial phyla (~80% of assigned reads), 3 archaeal phyla (~4%) and 59 eukaryotic phyla (~15%). Microbial diversity obtained from the WGS approach was compared with 16S rRNA gene results by mining WGS metagenomes, and we found similar estimates. The most frequently recovered bacterial sequences were Proteobacteria, predominantly comprised of 18.0-19.6% Planktomarina (Family Rhodobacteraceae) and 13.7-17.5% Candidatus Pelagibacter (Family Pelagibacterales). Other dominant bacterial genera, including Polaribacter (3.5-6.1%), Flavobacterium (1.8-2.6%), Sphingobacterium (1.4-1.6%) and Cellulophaga (1.4-2.0%), were members of Bacteroidetes and likely associated with the degradation and turnover of organic matter. The Marine Group I Archaea Nitrosopumilus was also detected. Remarkably, eukaryotic green alga Bathycoccus, Ostreococcus and Micromonas accounted for 8.8-15.2%, 3.6-4.9% and 2.1-3.1% of total read counts, respectively, highlighting their potential roles in the phytoplankton bloom after winter mixing.

Changchengzhania lutea gen. nov., sp. nov., a new member of the family Flavobacteriaceae isolated from Antarctic intertidal sediment

A Gram-negative, aerobic, yellow pigmented, non-flagellated, non-gliding, rod-shaped bacterial strain, designated SM1355^T, was isolated from Antarctic intertidal sediment collected near the Chinese Antarctic Great Wall Station. The strain grew at 4-35 °C and with 0.5-7.0 % (w/v) NaCl. It hydrolysed aesculin but didn't reduce nitrate to nitrite. Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain SM1355^T formed a distinct phylogenetic lineage within the family Flavobacteriaceae, sharing the highest 16S rRNA gene sequence similarity with Flaviramulus ichthyoenteri (96.3 %) and fairly high sequence similarities (95.0-96.0 %) with over 20 recognized species in eight genera of the family Flavobacteriaceae. The predominant fatty acids were anteiso-C15 : 0, iso-C15 : 0 and iso-C15 : 1 G. The major polar lipids were phosphatidylethanolamine and one unidentified lipid. The genomic DNA G+C content of strain SM1355^T was 36.2 mol%. Based on the results of the polyphasic characterization for strain SM1355^T, it is identified as the representative of a novel species in a new genus of the family Flavobacteriaceae, for which the name Changchengzhania lutea gen. nov., sp. nov. is proposed. The type strain of Changchengzhania lutea is SM1355^T (=JCM 30336^T=CCTCC AB 2014246^T).

Polaribacter insulae sp. nov., isolated from a tidal flat

A Gram-stain-negative, aerobic, non-motile and ovoid or rod-shaped bacterial strain, designated OITF-22^T, was isolated from a tidal flat of Oido, an island of South Korea, and subjected to a polyphasic taxonomic study. Strain OITF-22^T grew optimally at 25 °C, at pH 7.0-8.0 and in the presence of 2.0-3.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences showed that strain OITF-22^T fell within the clade comprising the type strains of Polaribacter species. Strain OITF-22^T exhibited 16S rRNA gene sequence similarity values of 97.2-99.4 % to the type strains of Polaribacter vadi, P. haliotis, P. atrinae, P. dokdonensis, P. litorisediminis,P. reichenbachii, P. irgensii and P. marinaquae, and of 93.0-96.9 % to the type strains of the other Polaribacter species. Strain OITF-22^T contained MK-6 as the predominant menaquinone and iso-C15 : 0 and iso-C15 : 0 3-OH as the major fatty acids. The major polar lipids detected in strain OITF-22^T were phosphatidylethanolamine and one unidentified lipid. The DNA G+C content of strain OITF-22^T was 32.3 mol% and its DNA-DNA relatedness values with the type strains of the eight phylogenetically most closely related Polaribacter species were 9-32 %. Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, revealed that strain OITF-22^T is separated from recognized species of the genus Polaribacter. On the basis of the data presented, strain OITF-22^T is considered to represent a novel species of the genus Polaribacter, for which the name Polaribacter insulae sp. nov. is proposed. The type strain is OITF-22^T (=KCTC 52658^T=NBRC 112706^T).

Larkinella ripae sp. nov., isolated from seashore soil

Strain 15J11-11^T was isolated from soil collected at the seashore and was Gram-staining-negative, short-rod-shaped, gliding and pale-pink pigmented. Flexirubin-type pigments were absent. The isolate grew at a temperature range of 15 to 30 °C and a pH range of 7 to 8. Comparative 16S rRNA gene sequence studies showed that strain 15J11-11^T belonged to the genus Larkinella within the phylum Bacteroidetes and was most closely related to Larkinella arboricola Z0532^T (95.6 %), Larkinella bovis M2TB15^T (95.4 %), and Larkinella insperata LMG 22510^T (95.2 %). The genomic DNA G+C content of strain 15J11-11^T was 53.2 mol%. The strain contained phosphatidylethanolamine, phosphatidylserine, an unidentified aminophospholipid and two unidentified polar lipids as the major polar lipids; menaquinone-7 as the predominant quinone and C16 : 1ω5c, iso-C15 : 0 and iso-C17 : 0 3-OH as the major fatty acids which supported the affiliation of strain 15J11-11^T to the genus Larkinella. Based on its phenotypic properties and phylogenetic distinctiveness, strain 15J11-11^T represents a novel species of the genus Larkinella, for which the name Larkinella ripae sp. nov. is proposed. The type strain is 15J11-11^T (=KCTC 42996^T=JCM 31657^T).

Polaribacter pacificus sp. nov., isolated from a deep-sea polymetallic nodule from the Eastern Pacific Ocean

A Gram-staining-negative, yellow-colony-forming, rod-shaped, non-flagellated and facultatively aerobic strain, designed HRA130-1T, was isolated from a deep-sea polymetallic nodule from the Pacific Clarion-Clipperton Fracture Zone (CCFZ). Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain HRA130-1T belonged to the genus Polaribacter (96.3-93.2 % 16S rRNA gene sequence similarity), and exhibited 94 % 16S rRNA gene sequence similarity to Polaribacter filamentus KCTC 23135T (type species) and the highest sequence similarity to Polaribacter huanghezhanensis KCTC 32516T (96.3 %). Optimal growth occurred in the presence of 4 % (w/v) NaCl, at pH 7.0 and 16 °C. The DNA G+C content of strain HRA130-1T was 35.9 mol%. The major fatty acid was iso-C15 : 0. The predominant respiratory quinone was menaquinone-6 (MK-6). The major polar lipids were phosphatidylethanolamine, phosphatidylglycerol, one unidentified phospholipid and an unidentified aminolipid. On the basis of data from the present taxonomic study using a polyphasic approach, strain HRA130-1T represents a novel species of the genus Polaribacter, for which the name Polaribacter pacificus sp. nov. is proposed. The type strain is HRA130-1T (=KCTC 52370T=MCCC 1K03199T=JCM 31460T=CGMCC 1.15763T).

Polaribacter litorisediminis sp. nov., isolated from a tidal flat

A Gram-stain-negative, aerobic, non-motile and ovoid or rod-shaped bacterial strain, designated OITF-11T, was isolated from a tidal flat in Oido, an island of South Korea, and subjected to a polyphasic taxonomic study. Strain OITF-11T grew optimally at 25 °C, at pH 7.0-8.0 and in the presence of 2.0 % (w/v) NaCl. The phylogenetic trees based on 16S rRNA gene sequences showed that strain OITF-11T belonged to the genus Polaribacter. Strain OITF-11T exhibited 16S rRNA gene sequence similarity values of 97.4-98.1 % to Polaribacter haliotis RA4-7T, Polaribacter atrinae KACC 17473T, Polaribacter dokdonensis DSW-5T and Polaribacter marinaquae KCTC 42664T, and of 94.1-96.9 % to the type strains of the other Polaribacter species. Strain OITF-11T contained menaquinone MK-6 as the predominant menaquinone and iso-C15 : 0, iso-C15 : 1 G, iso-C15 : 0 3-OH, iso-C17 : 0 3-OH and C15 : 1ω6c as the major fatty acids. The major polar lipids detected in strain OITF-11T were phosphatidylethanolamine, phosphatidylmonomethylethanolamine and one unidentified lipid. The DNA G+C content of strain OITF-11T was 32.2 mol% and its DNA-DNA relatedness values with the type strains of P. haliotis, P. atrinae, P. dokdonensis and P. marinaquae were 14-33 %. Differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain OITF-11T is separated from recognized species of the genus Polaribacter. On the basis of the data presented, strain OITF-11T is considered to represent a novel species of the genus Polaribacter, for which the name Polaribacter litorisediminis sp. nov. is proposed. The type strain is OITF-11T (=KCTC 52500T=NBRC 112457T).

Microbial Community Response to Terrestrially Derived Dissolved Organic Matter in the Coastal Arctic

Warming at nearly twice the global rate, higher than average air temperatures are the new ‘normal’ for Arctic ecosystems. This rise in temperature has triggered hydrological and geochemical changes that increasingly release carbon-rich water into the coastal ocean via increased riverine discharge, coastal erosion, and the thawing of the semi-permanent permafrost ubiquitous in the region. To determine the biogeochemical impacts of terrestrially derived dissolved organic matter (tDOM) on marine ecosystems we compared the nutrient stocks and bacterial communities present under ice-covered and ice-free conditions, assessed the lability of Arctic tDOM to coastal microbial communities from the Chukchi Sea, and identified bacterial taxa that respond to rapid increases in tDOM. Once thought to be predominantly refractory, we found that ∼7% of dissolved organic carbon and ∼38% of dissolved organic nitrogen from tDOM was bioavailable to receiving marine microbial communities on short 4 – 6 day time scales. The addition of tDOM shifted bacterial community structure toward more copiotrophic taxa and away from more oligotrophic taxa. Although no single order was found to respond universally (positively or negatively) to the tDOM addition, this study identified 20 indicator species as possible sentinels for increased tDOM. These data suggest the true ecological impact of tDOM will be widespread across many bacterial taxa and that shifts in coastal microbial community composition should be anticipated.

Spirosoma swuense sp. nov., isolated from wet soil

Strain JBM2-3T, a pale-yellow-coloured, aerobic, catalase-negative, oxidase-positive and Gram-stain-negative bacterium, was isolated from wet soil. The isolate grew aerobically at 25-30 °C (optimum 25 °C), pH 6.0-8.0 (optimum pH 7.0) and in the presence of 0-0.5 % (w/v) NaCl (optimum 0 % NaCl). Phylogenetic analysis based on 16S rRNA gene sequence indicated that strain JBM2-3T belonged to the genus Spirosoma, with a sequence similarity of 96.2 % with Spirosoma panaciterrae Gsoil 1519T. The strain showed the typical chemotaxonomic characteristics of the genus Spirosoma, with the presence of menaquinone 7 as the respiratory quinone; the major fatty acids were summed feature 3 (composed of C16: 1ω6c/ω7c), C16: 1ω5c and iso-C15: 0. The DNA G+C content of strain JBM2-3T was 47.4 mol%. The polar lipid profile contained major amounts of phosphatidylethanolamine and aminophospholipids. On the basis of its phenotypic and genotypic properties, and phylogenetic distinctiveness, strain JBM2-3T should be classified as a representative of a novel species in the genus Spirosoma, for which the name Spirosoma swuense sp. nov. is proposed. The type strain is JBM2-3T (=KCTC 52176T=JCM 31298T).

Microbial communities of aquatic environments on Heard Island characterized by pyrotag sequencing and environmental data

Heard Island in the Southern Ocean is a biological hotspot that is suffering the effects of climate change. Significant glacier retreat has generated proglacial lagoons, some of which are open to the ocean. We used pyrotag sequencing of SSU rRNA genes and environmental data to characterize microorganisms from two pools adjacent to animal breeding areas, two glacial lagoons and Atlas Cove (marine site). The more abundant taxa included Actinobacteria, Bacteroidetes and Proteobacteria, ciliates and picoflagellates (e.g. Micromonas), and relatively few Archaea. Seal Pool, which is rich in organic matter, was characterized by a heterotrophic degradative community, while the less eutrophic Atlas Pool had more eucaryotic primary producers. Brown Lagoon, with the lowest nutrient levels, had Eucarya and Bacteria predicted to be oligotrophs, possess small cell sizes, and have the ability to metabolize organic matter. The marine influence on Winston Lagoon was evident by its salinity and the abundance of marine-like Gammaproteobacteria, while also lacking typical marine eucaryotes indicating the system was still functioning as a distinct niche. This is the first microbiology study of Heard Island and revealed that communities are distinct at each location and heavily influenced by local environmental factors.