Spongiibacter marinus gen. nov., sp. nov., a halophilic marine bacterium isolated from the boreal sponge Haliclona sp. 1

Unraveling nitrogen removal performance during increasing loading rates in simultaneous nitrification and autotrophic denitrification: A functional and ecological analysis approach

Nitrogen contamination of water sources poses significant environmental and health risks. The sulfur-driven simultaneous nitrification and autotrophic denitrification (SNAD) process offers a cost-effective solution, as it operates in a single reactor, requires no organic carbon addition, and produces minimal sludge. However, this process remains underexplored, with microbial population dynamics, their interactions, and their implications for process efficiency not yet fully understood. To address this gap, this study analyzed microbial populations in a 0.8 L fluidized bed reactor performing sulfur-driven SNAD under increasing nitrogen loading rates (NLR), ranging from 11 to 105 g N/m3 d. The process achieved 93.5 % total nitrogen and 95.1 % ammonium removal at a hydraulic residence time (HRT) of 1.8 days. However, when the HRT was reduced to 0.96 days, nitrate removal instability occurred, reducing the nitrate removal efficiency to 42 %. Although increasing the HRT improved performance, two additional instability events were observed in subsequent stages at HRTs of 1.2 and 1.03 days, where nitrate removal efficiencies dropped to 11 % and 39 %, respectively. Functional analysis showed that NLR negatively impacted the proportion of sulfur-oxidizing bacteria, which was correlated with high nitrate levels in the effluent, although ammonium oxidation remained stable. Ecological network analysis revealed positive interactions between ammonia-oxidizing and heterotrophic bacteria, supporting nitrification stability. However, it also uncovered negative interactions between heterotrophic bacteria and sulfur-oxidizing denitrifiers, such as Dyella and Thiobacillus, suggesting these negative interactions contributed to temporary nitrogen removal problems in the system. This study highlights the importance of functional microbial and ecological network analyses over traditional metataxonomic approaches in understanding SNAD processes.

Marortus luteolus Yu et al. 2019 is a later heterotypic synonym of Zhongshania marina On et al. 2019

Phylogeny of 16S rRNA gene sequences showed that Marortus luteolus ZX-21T and Zhongshania marina DSW25-10T are closely related, and form a monophyletic clade affiliated with the genus Zhongshania. Whole genome sequence comparisons showed that M. luteolus ZX-21T and Z. marina DSW25-10T shared 78.8 % digital DNA-DNA hybridization, 97.6 % average nucleotide identity and 98.1 % average amino acid identity. These values exceeded the recommended threshold values for species delineation. Thus, based on the principle of priority, we propose the reclassification of Marortus luteolus Yu et al. 2019 as a later heterotypic synonym of Zhongshania marina On et al. 2019.

Dasania phycosphaerae sp. nov., isolated from phytoplankton sample from the south coast of the Republic of Korea

A novel bacterial strain, designated as GY-18T, was isolated from particulate material sampled from the Korean south coast. The bacterium was Gram-stain-negative, aerobic and rod-shaped. Oxidase and catalase were positive. Optimal growth was observed at 30 °C, pH 7.0, in the presence of 1 % (w/v) NaCl. Phylogenetic analyses based on 16S rRNA gene and whole-genome sequences suggested that strain GY-18T was a member of the genus Dasania , but represented a separate lineage. The 16S rRNA gene sequence of strain GY-18T showed high similarities to Dasania marina KCTC 12566T (98.4 %), Halioglobus japonicus KCTC 23429T (92.2 %), Marimicrobium arenosum KCTC 42300T (92.4 %) and Seongchinamella unica KCTC 62383T (92.2 %), respectively. The genome length of strain GY-18T was 3 808 450 bp with a DNA G+C content of 47.8 mol %. The major cellular fatty acids of strain GY-18T were summed feature 3 (comprising C16 : 1  ω7c and/or C16 : 1  ω6c), C16 : 0 and C10 : 0 3-OH (>10 %). Diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine and phospholipids were shown to be the major polar lipids. The predominant isoprenoid quinone was Q-8. Based on phylogenetic, phenotypic, chemotaxonomic and genomic features, we propose that strain GY-18T represents a novel species in the genus Dasania of the family Spongiibacteraceae , with the proposed name Dasania phycosphaerae sp. nov. The type strain is GY-18T (=KCTC 92290T=GDMCC 1.3586T).

Spongiibacter thalassae sp. nov., a marine gammaproteobacterium isolated from seawater

A bacterium, designated as KMU-166^T, belonging to the class Gammaproteobacteria, was isolated from seawater collected on the coastline of Dadaepo, Republic of Korea. Strain KMU-166^T was Gram-staining-negative, ovoid-shaped, motile, strictly aerobic, beige-colored, catalase-positive, and oxidase-negative; and had a chemoorganoheterotrophic metabolism. The novel isolate was found to grow at 1-4% NaCl concentrations (w/v), pH 6.5-9.5, and 10-40 °C. The 16S rRNA gene sequence-based phylogeny showed that strain KMU-166^T affiliates to the family Spongiibacteraceae and that it shared the greatest sequence similarity (96.4%) with Spongiibacter marinus HAL40b^T. The main (> 10%) cellular fatty acids were summed feature 3 (C16:1ω7c and/or C16:1ω6c), C17:1ω8c, and C18:1ω7c. The predominant respiratory quinone was ubiquinone-8 (Q-8). Strain KMU-166^T comprised phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, and two unidentified lipids. The assembled draft genome was 4.40 Mbp in size with a DNA G+C content of 55.7%. The average nucleotide identity, digital DNA-DNA hybridization, and average amino acid identity values of KMU-166^T and Spongiibacter marinus HAL40b^T, Spongiibacter tropicus CL-CB221^T, and "Spongiibacter pelagi" KMU-158^T were found to be 77.7-79.8%, 13.7-15.4%, and 66.1-70.9%, respectively. From the distinguishable polyphasic taxonomic results obtained, the strain is considered to represent a novel species of the genus Spongiibacter for which the name Spongiibacter thalassae sp. nov. is proposed. The type strain of S. thalassae sp. nov. is KMU-166^T (= KCCM 90449^T = NBRC 114308^T).

A Deep-Sea Bacterium Senses Blue Light via a BLUF-Dependent Pathway

Light is a ubiquitous energy source and environmental signal that broadly impacts the lifestyle of a large number of photosynthetic/nonphotosynthetic microorganisms living in the euphotic layer. However, the responses of deep-sea microbes to light are largely unknown, even though blue light is proposed to be distributed in the deep ocean. Here, we successfully cultured a novel bacterial species, named Spongiibacter nanhainus CSC3.9, from deep-sea cold seep samples by a blue light induction approach. The growth of strain CSC3.9 was obviously promoted by the illumination of blue light. We next determined BLUF (a typical blue light photoreceptor) was the most essential factor directing light sensing of strain CSC3.9 through a combined proteomic and genetic method. The function of light sensing mediated by BLUF was further confirmed by the in vitro-synthesized protein. Notably, homologs of BLUF widely existed across the marine microorganisms (containing Spongiibacter species) derived from different environments, including cold seeps. This strongly indicates that the distribution of light utilization by the nonphototrophic bacteria living in the ocean is broad and has been substantially underestimated.

IMPORTANCE Extensive studies have been conducted to explore the mechanisms of light sensing and utilization by microorganisms that live in the photic zone. Strikingly, accumulated evidence shows that light is distributed in the deep biosphere. However, the existence and process of light sensing and utilization by microbes inhabiting the deep ocean have been seldom reported. In the present study, a novel bacterial strain, Spongiibacter nanhainus CSC3.9, was enriched and purified from a deep-sea cold seep sample through a blue light induction method. Combined with genomic, proteomic, genetic, and biochemical approaches, the mechanism of this novel strain sensing blue light through a BLUF-dependent pathway was detailed. Our study provides a good model to study the mechanisms of light sensing mediated by deep-sea nonphototrophic bacteria.

Prokaryotic diversity of tropical coastal sand dunes ecosystem using metagenomics

Coastal sand dunes (CSDs), unique, stressed and hostile habitats act as a barrier between marine and terrestrial ecosystems. CSDs are stressed in terms of nutrition and fluctuating physio-chemical conditions. CSD is classified into several types, each of which presents different challenges for life forms. This study focuses on exploring bacterial and archaeal diversity and community structure in four CSD namely, Embryo, Fore, Gray, and Mature dunes of Keri beach, Goa along the west coast of India. The study was carried out using Next Generation Sequencing of hypervariable V3-V4 regions of the 16S rRNA gene using Illumina HiSeq platform. The present study hypothesizes that the prokaryotic communities at each dune may be different and could have different role in the ecosystem. The NGS for Embryo, Fore, Gray, and Mature dunes gave 1,045,447, 1,451,753, 1,321,867, and 1,537,758 paired-end reads, respectively, out of which 54,500, 50,032, 37,819, and 111,186 were retained through various quality filtrations. A total of 74, 63, 65, and 65% of OTUs, respectively, remained unknown at the species level. The highest bacterial and archaeal abundance was reported from Mature and Embryo dunes, respectively. Phylum Actinobacteria dominated the Embryo, Fore, and Mature dunes, whereas phylum Proteobacteria was the dominant in the Gray dune. Streptomyces was predominant in overall CSD followed by Bacillus, Acidobacterium, and Kouleothrix. The commonly and exclusively found members in each dune are cataloged. The highest species dominance, diversity, species richness, and abundance were observed in Embryo, Fore, Gray, and Mature dunes, respectively. The present study clearly elucidates that each dune has a distinct microbial community structure.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s13205-021-02809-5.

Electrochemical Bacterial Enrichment from Natural Seawater and Its Implications in Biocorrosion of Stainless-Steel Electrodes

Microbial electrochemical technologies have revealed the opportunity of electrochemical enrichment for specific bacterial groups that are able to catalyze reactions of interest. However, there are unsolved challenges towards their application under aggressive environmental conditions, such as in the sea. This study demonstrates the impact of surface electrochemical potential on community composition and its corrosivity. Electrochemical bacterial enrichment was successfully carried out in natural seawater without nutrient amendments. Experiments were carried out for ten days of exposure in a closed-flow system over 316L stainless steel electrodes under three different poised potentials (−150 mV, +100 mV, and +310 mV vs. Ag/AgCl). Weight loss and atomic force microscopy showed a significant difference in corrosion when +310 mV (vs. Ag/AgCl) was applied in comparison to that produced under the other tested potentials (and an unpoised control). Bacterial community analysis conducted using 16S rRNA gene profiles showed that poised potentials are more positive as +310 mV (vs. Ag/AgCl) resulted in strong enrichment for Rhodobacteraceae and Sulfitobacter. Hence, even though significant enrichment of the known electrochemically active bacteria from the Rhodobacteraceae family was accomplished, the resultant bacterial community could accelerate pitting corrosion in 316 L stainless steel, thereby compromising the durability of the electrodes and the microbial electrochemical technologies.

Marortus luteolus gen. nov., sp. nov., isolated from surface seawater of the East Sea in China

A Gram-stain-negative, motile, aerobic, rod-shaped bacterium with flagella, designated ZX-21^T, was isolated from surface seawater of the East Sea in Zhoushan, China. Growth of strain ZX-21T was observed at 10--35  o°C (optimum, 30 °C), at pH 6.0-8.5 (pHoptimum 6.5-7.0) and in the presence of 0.5-8 % (w/v) NaCl (optimum 3-4 %). It was positive for oxidase and catalase activity. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain ZX-21T constituted an independent lineage within the family Spongiibacteraceae and was most closely related to Zhongshania guokunii (96.83 %). Strain ZX-21T contained ubiquinone-8 (Q-8) as the sole isoprenoid quinone and summed feature 3 (C16 : 1ω77c and/or C16 : 1ω66c), summed feature 8 (C18 : 1ω77c and/or C18 : 1ω66c) and C16 : 0 as the major fatty acids. Phosphatidylglycerol (), phosphatidylethanolamine (), diphosphatidylglycerol () and an unidentified glycolipid were the major cellular polar lipids. The DNA G+C content was 49.1 mol%. Based on itsthe morphological, physiological and chemotaxonomic characteristics, strain ZX-21Tis described as a novel species in a novel genus for whichwith the name Marortus luteolus gen. nov., sp. nov. (type strain ZX-21T = MCCC 1K03431T=KCTC 62160T) is proposed.

Protist-Bacteria Associations: Gammaproteobacteria and Alphaproteobacteria Are Prevalent as Digestion-Resistant Bacteria in Ciliated Protozoa

Protistan bacterivory, a microbial process involving ingestion and digestion, is ecologically important in the microbial loop in aquatic and terrestrial ecosystems. While bacterial resistance to protistan ingestion has been relatively well understood, little is known about protistan digestion in which some ingested bacteria could not be digested in cells of major protistan grazers in the natural environment. Here we report the phylogenetic identities of digestion-resistant bacteria (DRB) that could survive starvation and form relatively stable associations with 11 marine and one freshwater ciliate species. Using clone library and sequencing of 16S rRNA genes, we found that the protistan predators could host a high diversity of DRB, most of which represented novel bacterial taxa that have not been cultivated. The localization inside host cells, quantity, and viability of these bacteria were checked using fluorescence in situ hybridization. The DRB were affiliated with Actinobacteria, Bacteroidetes, Firmicutes, Parcubacteria (OD1), Planctomycetes, and Proteobacteria, with Gammaproteobacteria and Alphaproteobacteria being the most frequently occurring classes. The dominance of Gamma- and Alphaproteobacteria corresponds well to a previous study of Global Ocean Sampling metagenomic data showing the widespread types of bacterial type VI and IV secretion systems (T6SS and T4SS) in these two taxa, suggesting a putatively significant role of secretion systems in promoting marine protist-bacteria associations. In the DRB assemblages, opportunistic bacteria such as Alteromonadaceae, Pseudoalteromonadaceae, and Vibrionaceae often presented with high proportions, indicating these bacteria could evade protistan grazing thus persist and accumulate in the community, which, however, contrasts with their well-known rarity in nature. This begs the question whether viral lysis is significant in killing these indigestible bacteria in microbial communities. Taken together, our study on the identity of DRB sheds new light on microbial interactions and generates further hypotheses including the potential importance of bacterial protein secretion systems in structuring bacterial community composition and functioning of “microbial black box” in aquatic environments.

Litorivivens lipolytica gen. nov., sp. nov., a lipolytic bacterium isolated from a tidal flat

A Gram-stain-negative, flagellated, aerobic and rod-shaped or ovoid bacterial strain, designated HJTF-7(T), was isolated from a tidal flat on the South Sea of South Korea, and its taxonomic position was investigated using a polyphasic approach. Strain HJTF-7(T) grew optimally at 25 °C, at pH 7.0-8.0 and in the presence of 2.0% (w/v) NaCl. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees, based on 16S rRNA gene sequences, showed that strain HJTF-7(T) joined the cluster comprising the type strains of species of the genera Spongiibacter and Zhongshania. Strain HJTF-7(T) exhibited 16S rRNA gene sequence similarities of 90.4-92.5% to the type strains of species of the genera Spongiibacter and Zhongshania and of less than 91.5% to the type strains of other recognized species. Strain HJTF-7(T) contained Q-8 as the predominant ubiquinone. The major fatty acids were iso-C17:1ω9c, iso-C15:0, iso-C17:0, iso-C11:0 3-OH and C17:1ω8c and the major polar lipids were phosphatidylethanolamine and phosphatidylglycerol. The fatty acid and polar lipid profiles of strain HJTF-7(T) were distinct from those of members of the genera Spongiibacter and Zhongshania. The DNA G+C content of strain HJTF-7(T) was 55.9 mol%. The phylogenetic data and differential chemotaxonomic and other phenotypic properties revealed that strain HJTF-7(T) represents a novel genus and species within the class Gammaproteobacteria, for which the name Litorivivens lipolytica gen. nov., sp. nov. is proposed. The type strain of Litorivivens lipolytica is HJTF-7(T) ( =KCTC 42157(T) =CECT 8654(T)).

Zhongshania aliphaticivorans sp. nov., an aliphatic hydrocarbon-degrading bacterium isolated from marine sediment, and transfer of Spongiibacter borealis Jang et al. 2011 to the genus Zhongshania as Zhongshania borealis comb. nov

A Gram-staining-negative, facultatively aerobic bacterium, designated SM-2(T), was isolated from a sea-tidal flat of Yellow Sea, South Korea. Cells were catalase- and oxidase-positive motile rods with a single polar flagellum. Growth of strain SM-2(T) was observed at 10-37 °C (optimum, 25-30 °C), at pH 5.5-8.5 (optimum, pH 7.0-7.5) and in the presence of 0-11% (w/v) NaCl (optimum, 2%). Strain SM-2(T) contained ubiquinone-8 (Q-8) as the sole isoprenoid quinone and C(17:1)ω8c, summed feature 3 (comprising C(16:1)ω7c and/or iso-C(15:0) 2-OH), C(17:0) and C(18:1)ω7c as the major fatty acids. Phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an unidentified lipid were identified as the major cellular polar lipids. The G+C content of the genomic DNA was 52.2 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain SM-2(T) formed a tight phyletic lineage with Zhongshania antarctica ZS5-23(T), Zhongshania guokunii ZS6-22(T) and Spongiibacter borealis CL-AS9(T), but that S. borealis CL-AS9(T) was distinct from other species of the genus Spongiibacter. Based on 16S rRNA gene sequence similarities, strain SM-2(T) was most closely related to S. borealis CL-AS9(T), Z. antarctica ZS5-23(T) and Z. guokunii ZS6-22(T), with similarities of 99.5%, 98.9% and 98.7%, respectively, but the DNA-DNA hybridization values among these species were clearly lower than 70%. On the basis of chemotaxonomic data and molecular properties, we propose strain SM-2(T) represents a novel species of the genus Zhongshania with the name Zhongshania aliphaticivorans sp. nov. (type strain SM-2(T) =KACC 18120(T) =JCM 30138(T)). We also propose the transfer of Spongiibacter borealis Jang et al. 2011 to the genus Zhongshania as Zhongshania borealis comb. nov. (type strain CL-AS9(T) =KCCM 90094(T) =JCM 17304(T)).

Taxonomy and evolution of bacteriochlorophyll a-containing members of the OM60/NOR5 clade of marine gammaproteobacteria: description of Luminiphilus syltensis gen. nov., sp. nov., reclassification of Haliea rubra as Pseudohaliea rubra gen. nov., comb. nov., and emendation of Chromatocurvus halotolerans

Background

Aerobic gammaproteobacteria affiliated to the OM60/NOR5 clade are widespread in saline environments and of ecological importance in several marine ecosystems, especially the euphotic zone of coastal areas. Within this group a close relationship between aerobic anoxygenic photoheterotrophs and non-phototrophic members has been found.

Results

Several strains of aerobic red-pigmented bacteria affiliated to the OM60/NOR5 clade were obtained from tidal flat sediment samples at the island of Sylt (North Sea, Germany). Two of the novel isolates, Rap1red and Ivo14^T, were chosen for an analysis in detail. Strain Rap1red shared a 16S rRNA sequence identity of 99% with the type strain of Congregibacter litoralis and was genome-sequenced to reveal the extent of genetic microheterogeneity among closely related strains within this clade. In addition, a draft genome sequence was obtained from the isolate Ivo14^T, which belongs to the environmental important NOR5-1 lineage that contains so far no cultured representative with a comprehensive description. Strain Ivo14^T was characterized using a polyphasic approach and compared with other red-pigmented members of the OM60/NOR5 clade, including Congregibacter litoralis DSM 17192^T, Haliea rubra DSM 19751^T and Chromatocurvus halotolerans DSM 23344^T. All analyzed strains contained bacteriochlorophyll a and spirilloxanthin as photosynthetic pigments. Besides a detailed phenotypic characterization including physiological and chemotaxonomic traits, sequence information based on protein-coding genes and a comparison of draft genome data sets were used to identify possible features characteristic for distinct taxa within this clade.

Conclusions

Comparative sequence analyses of the pufLM genes of genome-sequenced representatives of the OM60/NOR5 clade indicated that the photosynthetic apparatus of these species was derived from a common ancestor and not acquired by multiple horizontal gene transfer from phylogenetically distant species. An affiliation of the characterized bacteriochlorophyll a-containing strains to different genera was indicated by significant phenotypic differences and pufLM nucleotide sequence identity values below 82%. The revealed high genotypic and phenotypic diversity of closely related strains within this phylogenetic group reflects a rapid evolution and frequent niche separation in the OM60/NOR5 clade, which is possibly driven by the necessities of an adaptation to oligotrophic marine habitats.

Alkane biodegradation genes from chronically polluted subantarctic coastal sediments and their shifts in response to oil exposure

Although sediments are the natural hydrocarbon sink in the marine environment, the ecology of hydrocarbon-degrading bacteria in sediments is poorly understood, especially in cold regions. We studied the diversity of alkane-degrading bacterial populations and their response to oil exposure in sediments of a chronically polluted Subantarctic coastal environment, by analyzing alkane monooxygenase (alkB) gene libraries. Sequences from the sediment clone libraries were affiliated with genes described in Proteobacteria and Actinobacteria, with 67 % amino acid identity in average to sequences from isolated microorganisms. The majority of the sequences were most closely related to uncultured microorganisms from cold marine sediments or soils from high latitude regions, highlighting the role of temperature in the structuring of this bacterial guild. The distribution of alkB sequences among samples of different sites and years, and selection after experimental oil exposure allowed us to identify ecologically relevant alkB genes in Subantarctic sediments, which could be used as biomarkers for alkane biodegradation in this environment. 16 S rRNA amplicon pyrosequencing indicated the abundance of several genera for which no alkB genes have yet been described (Oleispira, Thalassospira) or that have not been previously associated with oil biodegradation (Spongiibacter-formerly Melitea-, Maribius, Robiginitomaculum, Bizionia and Gillisia). These genera constitute candidates for future work involving identification of hydrocarbon biodegradation pathway genes.

Halioglobus japonicus gen. nov., sp. nov. and Halioglobus pacificus sp. nov., members of the class Gammaproteobacteria isolated from seawater

Two coccoid, non-motile bacteria were isolated from seawater in the north-western Pacific Ocean near Japan. The two strains, designated S1-36T and S1-72T, were Gram-negative, obligately aerobic, heterotrophic and catalase-negative. They were able to reduce nitrate to nitrogen. Both strains required NaCl for growth, with optimum growth in 2 % NaCl, and grew at 15–30 °C, with optimum growth at 20–25 °C. Genomic DNA G+C contents of strains S1-36T and S1-72T were 59.6 and 59.4 mol%, respectively. The predominant isoprenoid quinone was Q-8 and major cellular fatty acids were C16 : 1ω7c, C18 : 1ω7c and C17 : 1ω8c. Analyses of 16S rRNA gene sequences revealed that strains S1-36T and S1-72T were related to each other (96.1 % sequence similarity) and both strains showed 92.3–94.7 % sequence similarity with members of the genus Haliea . On the basis of phenotypic and phylogenetic features, strains S1-36T and S1-72T should be classified as representatives of two novel species in a new genus, Halioglobus gen. nov., within the class Gammaproteobacteria . The names proposed are Halioglobus japonicus sp. nov., the type species of the genus, with S1-36T ( = NBRC 107739T = KCTC 23429T) as type strain, and Halioglobus pacificus sp. nov., with S1-72T ( = NBRC 107742T = KCTC 23430T) as type strain.

Description of Spongiibacter borealis sp. nov., isolated from Arctic seawater, and reclassification of Melitea salexigens Urios et al. 2008 as a later heterotypic synonym of Spongiibacter marinus Graeber et al. 2008 with emended descriptions of the genus Spongiibacter and Spongiibacter marinus

A Gram-negative, rod-shaped and motile strain, designated CL-AS9(T), was isolated from polar seawater of the Arctic. Analysis of the 16S rRNA gene sequence of the strain showed an affiliation with the genus Spongiibacter, sharing 93.9% and 93.7% sequence similarities with the type strains of Spongiibacter tropicus CL-CB221(T) and Spongiibacter marinus HAL40b(T), respectively. Phylogenetic analyses revealed that strain CL-AS9(T) formed a separate branch that was distinct from a clade comprising Spongiibacter marinus HAL40b(T), Spongiibacter tropicus CL-CB221(T) and Melitea salexigens 5IX/A01/131(T). Cells of the strain grew optimally at 20-25 °C and pH 6.6-8.0 in the presence of 3-4% (w/v) sea salts. The major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and an unidentified aminophospholipid. The major quinone was ubiquinone 8. The major cellular fatty acids were C(16:1)ω7c and/or iso-C(15:0) 2-OH (23.1%), C(17:1)ω8c (22.1%) and C(18:1)ω7c (15.6%). The genomic DNA G+C content was 53.6 mol%. Based on the phylogenetic, chemotaxonomic and phenotypic data presented, we propose the name Spongiibacter borealis sp. nov. with the type strain CL-AS9(T) (=KCCM 90094(T) =JCM 17304(T)) and the reclassification of Melitea salexigens as a later heterotypic synonym of Spongiibacter marinus. We also provide emended descriptions of the genus Spongiibacter and Spongiibacter marinus.

Zhongshania antarctica gen. nov., sp. nov. and Zhongshania guokunii sp. nov., gammaproteobacteria respectively isolated from coastal attached (fast) ice and surface seawater of the Antarctic

Two Gram-negative, motile, aerobic, catalase- and oxidase-positive, rod-shaped strains, designated ZS5-23(T) and ZS6-22(T), were respectively isolated from Antarctic coastal attached (fast) ice and surface seawater samples. Both strains could grow at 4-35 °C (optimum 30 °C) and in the absence of NaCl. Analyses of 16S rRNA gene sequences revealed that strains ZS5-23(T) and ZS6-22(T) were closely related to each other (99.0 % sequence similarity) and belonged to the class Gammaproteobacteria, with their closest relatives being Spongiibacter and Melitea species (93.1-94.3 % sequence similarity). The predominant cellular fatty acids in both strains were C₁₇:₁ω8c, C₁₇:₀ and summed feature 3 (C₁₆:₁ω7c and/or iso-C₁₅:₀ 2-OH). Genomic DNA G+C contents of strains ZS5-23(T) and ZS6-22(T) were 51.5 and 51.8 mol%, respectively. The DNA-DNA relatedness between strains ZS5-23(T) and ZS6-22(T) was 50.9 %. Strains ZS5-23(T) and ZS6-22(T) could be differentiated from each other and from Spongiibacter and Melitea species by differences in a number of phenotypic properties. Based on the data presented, strains ZS5-23(T) and ZS6-22(T) represent two novel species in a new genus in the class Gammaproteobacteria, for which the names Zhongshania antarctica gen. nov., sp. nov. (the type species) and Zhongshania guokunii sp. nov. are proposed. The type strain of Zhongshania antarctica is ZS5-23(T) ( = KACC 14066(T)  = CCTCC AB 209246(T)) and that of Zhongshania guokunii is ZS6-22(T) ( = KACC 14532(T)  = CCTCC AB 209247(T)).

Arenicella xantha gen. nov., sp. nov., a gammaproteobacterium isolated from a marine sandy sediment

A Gram-negative, aerobic, yellow-pigmented, rod-shaped, non-motile bacterium, strain KMM 3895T, was isolated from a marine sandy sample collected offshore from the Sea of Japan. Phylogenetic analysis based on the 16S rRNA gene sequence placed strain KMM 3895T in the class Gammaproteobacteria, forming a separate branch, sharing 89.5 % sequence similarity with Nitrincola lacisaponensis 4CAT and 88–87 % similarity with the other members of the cluster, including members of Kangiella, Spongiibacter, Alcanivorax and Microbulbifer. The major isoprenoid quinone was Q-8. Polar lipids consisted of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, aminophospholipid and an unknown phospholipid. Fatty acid analysis revealed C16 : 1 ω7, iso-C16 : 0, iso-C18 : 0 and C18 : 1 ω7 as dominant components. The DNA G+C content was determined to be 48.1 mol%. Based on its unique phenotypic characteristics and phylogenetic distance, the marine coastal sediment isolate KMM 3895T should be classified as a representative of a novel genus and species, for which the name Arenicella xantha gen. nov., sp. nov. is proposed. The type strain of Arenicella xantha is KMM 3895T (=NRIC 0759T =JCM 16153T).

Porticoccus litoralis gen. nov., sp. nov., a gammaproteobacterium isolated from the Yellow Sea

A marine bacterium, designated IMCC2115T, was isolated from coastal seawater (Yellow Sea, Korea) using a high throughput cultivation method based on dilution-to-extinction, and taxonomically investigated. Cells of the strain formed tiny, beige to off-white colonies and were Gram-stain-negative, obligately aerobic, chemoheterotrophic, non-motile cocci. Based on 16S rRNA gene sequence comparisons, the strain was most closely related to the genera Marinimicrobium (92.0–92.4 %) and Microbulbifer (91.6–92.8 %), but phylogenetic trees showed that the strain formed a distinct phyletic line in the class Gammaproteobacteria adjacent to the OM60 and SAR92 clades. The DNA G+C content of the strain was 47.8 mol% and the predominant cellular fatty acids were anteiso-C15 : 0 (67.6 %), anteiso-C17 : 0 (14.4 %) and C16 : 0 (6.9 %). The 16S rRNA gene sequence analyses and phenotypic and chemotaxonomic tests allowed the differentiation of IMCC2115T from other related genera in the class Gammaproteobacteria. Therefore, strain IMCC2115T (=KCCM 42369T =NBRC 102686T) is proposed as the representative of a new genus and species, for which the name Porticoccus litoralis gen. nov., sp. nov. is proposed.

The photosynthetic apparatus and its regulation in the aerobic gammaproteobacterium Congregibacter litoralis gen. nov., sp. nov

BACKGROUND

There is accumulating evidence that in some marine environments aerobic bacteriochlorophyll a-producing bacteria represent a significant part of the microbial population. The interaction of photosynthesis and carbon metabolism in these interesting bacteria is still largely unknown and requires further investigation in order to estimate their contribution to the marine carbon cycle.

METHODOLOGY/PRINCIPAL FINDINGS

Here, we analyzed the structure, composition and regulation of the photosynthetic apparatus in the obligately aerobic marine gammaproteobacterium KT71(T). Photoheterotrophically grown cells were characterized by a poorly developed lamellar intracytoplasmic membrane system, a type 1 light-harvesting antenna complex and a photosynthetic reaction center associated with a tetraheme cytochrome c. The only photosynthetic pigments produced were bacteriochlorophyll a and spirilloxanthin. Under semiaerobic conditions KT71(T) cells expressing a photosynthetic apparatus showed a light-dependent increase of growth yield in the range of 1.3-2.5 fold. The expression level of the photosynthetic apparatus depended largely on the utilized substrate, the intermediary carbon metabolism and oxygen tension. In addition, pigment synthesis was strongly influenced by light, with blue light exerting the most significant effect, implicating that proteins containing a BLUF domain may be involved in regulation of the photosynthetic apparatus. Several phenotypic traits in KT71(T) could be identified that correlated with the assumed redox state of growing cells and thus could be used to monitor the cellular redox state under various incubation conditions.

CONCLUSIONS/SIGNIFICANCE

In a hypothetical model that explains the regulation of the photosynthetic apparatus in strain KT71(T) we propose that the expression of photosynthesis genes depends on the cellular redox state and is maximal under conditions that allow a balanced membrane redox state. So far, bacteria capable of an obligately aerobic, photosynthetic metabolism constitute a unique phenotype within the class Gammaproteobacteria, so that it is justified to propose a new genus and species, Congregibacter litoralis gen. nov, sp. nov., represented by the type strain KT71(T) ( = DSM 17192(T) = NBRC 104960(T)).