Seasonality in land-ocean connectivity and local processes control sediment bacterial community structure and function in a High Arctic tidal flat

Climate change is altering patterns of precipitation, cryosphere thaw, and land-ocean influxes, affecting understudied Arctic estuarine tidal flats. These transitional zones between terrestrial and marine systems are hotspots for biogeochemical cycling, often driven by microbial processes. We investigated surface sediment bacterial community composition and function from May to September along a river-intertidal-subtidal-fjord gradient. We paired metabarcoding of in situ communities with in vitro carbon-source utilization assays. Bacterial communities differed in space and time, alongside varying environmental conditions driven by local seasonal processes and riverine inputs, with salinity emerging as the dominant structuring factor. Terrestrial and riverine taxa were found throughout the system, likely transported with runoff. In vitro assays revealed sediment bacteria utilized a broader range of organic matter substrates when incubated in fresh and brackish water compared to marine water. These results highlight the importance of salinity for ecosystem processes in these dynamic tidal flats, with the highest potential for utilization of terrestrially derived organic matter likely limited to tidal flat areas (and times) where sediments are permeated by freshwater. Our results demonstrate that intertidal flats must be included in future studies on impacts of increased riverine discharge and transport of terrestrial organic matter on coastal carbon cycling in a warming Arctic.

Hydrocarbon biodegradation potential of microbial communities from high Arctic beaches in Canada's Northwest Passage

Sea ice loss is opening shipping routes in Canada's Northwest Passage, increasing the risk of an oil spill. Harnessing the capabilities of endemic microorganisms to degrade oil may be an effective remediation strategy for contaminated shorelines; however, limited data exists along Canada's Northwest Passage. In this study, hydrocarbon biodegradation potential of microbial communities from eight high Arctic beaches was assessed. Across high Arctic beaches, community composition was distinct, potential hydrocarbon-degrading genera were detected and microbial communities were able to degrade hydrocarbons (hexadecane, naphthalene, and alkanes) at low temperature (4 °C). Hexadecane and naphthalene biodegradation were stimulated by nutrients, but nutrients had little effect on Ultra Low Sulfur Fuel Oil biodegradation. Oiled microcosms showed a significant enrichment of Pseudomonas and Rhodococcus. Nutrient-amended microcosms showed increased abundances of key hydrocarbon biodegradation genes (alkB and CYP153). Ultimately, this work provides insight into hydrocarbon biodegradation on Arctic shorelines and oil-spill remediation in Canada's Northwest Passage.

Urechidicola croceus gen. nov., sp. nov., a member of the family Flavobacteriaceae

A Gram-stain-negative, rod-shaped, non-flagellated, non-gliding, aerobic bacterial strain, designated LPB0138T, was isolated from a marine spoon worm (Urechis unicinctus). The strain LPB0138T contains a circular chromosome of 3.43 Mb with a DNA G+C content of 30.4 mol%. The genome includes 2987 protein-coding genes and two copies of rRNA operons. The 16S rRNA gene sequence analysis showed that the isolate occurred within a clade containing only members of the family Flavobacteriaceae . The highest sequence similarity was observed with the genus Lutibacter (93.0–94.3 %), but the phylogenetic leaf of the new isolate did not belong to any of the genera known in the family Flavobacteriaceae . The low sequence similarity and the phylogenetic tree topology implied the novel generic status of the new isolate. The phenotypic properties of the strain LPB0138T also differentiated this isolate from its neighbour genera by showing a distinctive fatty acid composition, unique polar lipids profile, and low DNA G+C content. The LPB0138T strain contained menaquinone 6 as the isoprenoid quinone; iso-C15 : 1 G, iso-C15 : 0, iso-C15 : 0 3-OH, and iso-C17 : 0 3-OH as the major fatty acids; and phosphatidylethanolamine, unidentified aminophospholipids, unidentified aminolipids, and unidentified lipids as the major polar lipids. Based on the polyphasic taxonomic data obtained, the LPB0138T strain is considered to represent a novel species in a novel genus of the family Flavobacteriaceae, for which the name Urechidicola croceus gen. nov., sp. nov. was proposed. The type strain is LPB0138T (=KACC 18889T;=JCM 31563T).

Diversity patterns and isolation of Planctomycetes associated with metalliferous deposits from hydrothermal vent fields along the Valu Fa Ridge (SW Pacific)

The microbial diversity associated with diffuse venting deep-sea hydrothermal deposits is tightly coupled to the geochemistry of the hydrothermal fluids. Previous 16S rRNA gene amplicon sequencing (metabarcoding) of marine iron-hydroxide deposits along the Arctic Mid Ocean Ridge, revealed the presence of diverse bacterial communities associated with these deposits (Storesund and Øvreås in Antonie van Leeuwenhoek 104:569-584, 2013). One of the most abundant and diverse phyla detected was the enigmatic Planctomycetes. Here we report on the comparative analyses of the diversity and distribution patterns of Planctomycetes associated with metalliferous deposits from two diffuse-flow hydrothermal vent fields (Mariner and Vai Lili) from the Valu Fa Ridge in the Southwestern Pacific. Metabarcoding of 16S rRNA genes showed that the major prokaryotic phyla were Proteobacteria (51-73% of all 16S rRNA gene reads), Epsilonbacteraeota (0.5-19%), Bacteriodetes (5-17%), Planctomycetes (0.4-11%), Candidatus Latescibacteria (0-5%) and Marine Benthic Group E (Hydrothermarchaeota) (0-5%). The two different sampling sites differed considerably in overall community composition. The abundance of Planctomycetes also varied substantially between the samples and the sites, with the majority of the sequences affiliated with uncultivated members of the classes Planctomycetacia and Phycisphaerae, and other deep branching lineages. Seven different strains affiliated with the order Planctomycetales were isolated, mostly from the Vai Lili samples, where also the highest Planctomycetales diversity was seen. Most of the isolates were affiliated with the genera Gimesia, Rhodopirellula and Blastopirellula. One isolate was only distantly related to known cultured, but uncharacterized species within the Pir4 group. This study shows that the deep-sea Planctomycetes represent a very heterogeneous group with a high phylogenetic diversity and a substantial potential for novel organism discovery in these deep ocean environments.

Biogeographic Differences in the Microbiome and Pathobiome of the Coral Cladocora caespitosa in the Western Mediterranean Sea

The endemic Mediterranean zooxanthellate scleractinian reef-builder Cladocora caespitosa is among the organisms most affected by warming-related mass mortality events in the Mediterranean Sea. Corals are known to contain a diverse microbiota that plays a key role in their physiology and health. Here we report the first study that examines the microbiome and pathobiome associated with C. caespitosa in three different Mediterranean locations (i.e., Genova, Columbretes Islands, and Tabarca Island). The microbial communities associated with this species showed biogeographical differences, but shared a common core microbiome that probably plays a key role in the coral holobiont. The putatively pathogenic microbial assemblage (i.e., pathobiome) of C. caespitosa also seemed to depend on geographic location and the human footprint. In locations near the coast and with higher human influence, the pathobiome was entirely constituted by Vibrio species, including the well-known coral pathogens Vibrio coralliilyticus and V. mediterranei. However, in the Columbretes Islands, located off the coast and the most pristine of the analyzed locations, no changes among microbial communities associated to healthy and necrosed samples were detected. Hence, our results provide new insights into the microbiome of the temperate corals and its role in coral health status, highlighting its dependence on the local environmental conditions and the human footprint.

Description of Lutimonas halocynthiae sp. nov., isolated from a golden sea squirt (Halocynthia aurantium), reclassification of Aestuariicola saemankumensis as Lutimonas saemankumensis comb. nov. and emended description of the genus Lutimonas

A Gram-stain-negative, non-motile, coccoid, ovoid or rod-shaped bacterial strain, designated RSS3-C1T, was isolated from a golden sea squirt (Halocynthia aurantium) collected from the East Sea, South Korea. Strain RSS3-C1T was found to grow optimally at 20–25 °C, at pH 7.0–8.0 and in the presence of 2.0 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences revealed that strain RSS3-C1T clustered with the type strains of Lutimonas vermicola and Aestuariicola saemankumensis . Strain RSS3-C1T exhibited 98.8 % 16S rRNA gene sequence similarity to each type strain. Strain RSS3-C1T contained MK-6 as the predominant menaquinone and iso-C15 : 0, iso-C17 : 0 3-OH and anteiso-C15 : 0 as the major fatty acids. The major polar lipids of strain RSS3-C1T were phosphatidylethanolamine and two unidentified lipids. The DNA G+C content of strain RSS3-C1T was 39.2 mol%, and DNA–DNA relatedness to the type strains of and was 21±5.3 and 26±7.5 %, respectively. The differential phenotypic properties, together with its phylogenetic and genetic distinctiveness, revealed that strain RSS3-C1T is separated from and . On the basis of the data presented, strain RSS3-C1T is considered to represent a novel species of the genus Lutimonas , for which the name Lutimonas halocynthiae sp. nov. is proposed. The type strain is RSS3-C1T ( = KCTC 32537T = CECT 8444T). In this study, it is also proposed that Aestuariicola saemankumensis should be reclassified as a member of the genus Lutimonas , as Lutimonas saemankumensis comb. nov. (type strain SMK-142T = KCTC 22171T = CCUG 55329T), and the description of the genus Lutimonas is emended.

Ochrovirga pacifica gen. nov., sp. nov., a novel agar-lytic marine bacterium of the family Flavobacteriaceae isolated from a seaweed

A strain designated as S85(T) was isolated from a seaweed collected from coastal area of Chuuk State in Micronesia. The strain was gram-negative, rod-shaped, and non-motile and formed yellow colonies on the SWY agar (0.2 % yeast extract and 1.5 % agar in seawater) and Marine agar 2216. The strain grew at pH 5-9 (optimum, pH 8), at 15-40 °C (optimum, 25-28 °C), and with 1-9 % (w/v) NaCl (optimum, 3 %). The phylogenetic analysis based on 16S rRNA gene sequence showed that strain S85(T) was related to Lutibacter litoralis CL-TF09(T) and Maritimimonas rapanae A31(T) with 91.4 % and with 90.5 % similarity, respectively. The dominant fatty acids were iso-C15:0, iso-C15:0 3-OH and iso-C17:0 3-OH, C16:0 3-OH and summed feature 3 (C16:1 ω7c and/or iso-C15:0 2-OH). The major isoprenoid quinone was MK-6. The DNA G+C content of the type strain was 34.6 mol %. The major polar lipids were phosphatidylethanolamine, an unknown glycolipid and two unknown polar lipids. Based on this polyphasic taxonomic data, strain S85(T) stands for a novel species of a new genus, and we propose the name Ochrovirga pacifica gen. nov., sp. nov. The type strain of O. pacifica is S85(T) (=KCCM 90106 =JCM 18327(T)).

Long-term microfouling on commercial biocidal fouling control coatings

The current study investigated the microbial community composition of the biofilms that developed on 11 commercial biocidal coatings, including examples of the three main historic types, namely self-polishing copolymer (SPC), self-polishing hybrid (SPH) and controlled depletion polymer (CDP), after immersion in the sea for one year. The total wet weight of the biofilm and the total bacterial density were significantly influenced by all coatings. Pyrosequencing of 16S rRNA genes revealed distinct bacterial community structures on the different types of coatings. Flavobacteria accounted for the dissimilarity between communities developed on the control and SPC (16%) and the control and SPH coatings (17%), while Alphaproteobacteria contributed to 14% of the dissimilarity between the control and CDP coatings. The lowest number of operational taxonomic units was found on Intersmooth 100, while the lowest biomass and density of bacteria was detected on other SPC coatings. The experiments demonstrated that the nature and quantity of biofilm present differed from coating to coating with clear differences between copper-free and copper-based biocidal coatings.

Aureivirga marina gen. nov., sp. nov., a marine bacterium isolated from the Mediterranean sponge Axinella verrucosa

Two bacterial strains, VI.14 and VIII.04T, were isolated from the Mediterranean sponge Axinella verrucosa collected off the Israeli coast near Sdot Yam. The non-motile, aerobic, Gram-negative isolates were oxidase-negative and catalase-positive, and formed golden-brown colonies on marine agar 2216. The pigment was neither diffusible nor flexirubin-like. Strain VIII.04T grew at 15–37 °C, at pH 6.0–9.0, in the presence of 20–50 g NaCl l−1 and 20–80 g sea salts l−1, The spectrum was narrower for strain VI.14, with growth at pH 7.0–8.0. and in the presence of 30–50 g NaCl l−1 and 30–70 g sea salts l−1. The predominant fatty acid (>50 %) in both strains was iso-C15 : 0, and the major respiratory quinone was MK-6. The DNA G+C content was 30.7 and 31.1 mol% for VIII.04T and VI.14, respectively. Results from 16S rRNA sequence similarity and phylogenetic analyses indicated that both strains are closely related to members of the family Flavobacteriaceae within the phylum Bacteroidetes , with as much as 91.7 % 16S rRNA sequence similarity. On the basis of data from the polyphasic analysis, we suggest that the strains represent a novel species in a new genus within the family Flavobacteriaceae , for which the name Aureivirga marina gen. nov., sp. nov. is proposed. Strain VIII.04T ( = ATCC BAA-2394T = LMG 26721T) is the type strain of Aureivirga marina.