Family Alteromonadaceae Research Articles

Unraveling microbial community variation along a salinity gradient and indicative significance to groundwater salinization in the coastal aquifer

Saltwater intrusion poses a global environmental challenge in coastal regions, profoundly influencing groundwater microbial communities and biogeochemical processes. This study aims to elucidate the origin of groundwater salinity and understand the response of microbial interactions to groundwater salination through stable isotopes and 16S rDNA gene sequencing. The findings reveal a significant increase in groundwater TDS from inland to the coastline, ranging from 0.5 g/L to 144.6 g/L. Ionic relationship and isotopic fractionation indicate that the high salinity in groundwater originates not only from paleo–seawater but also from the dissolution of halite. Salty groundwater exhibits lower species richness and diversity than fresh groundwater. TDS, SO42–, and NO2– are the pivotal factors shaping the microbial community of salty groundwater, while NO3– and H2SiO3 are dominant variables influencing fresh groundwater community. This study identifies the order Alteromonadales, family Alteromonadaceae, and genus Marinobacter as potential biomarkers of seawater or paleo–seawater sources. Phylogenetic molecular network analysis of microbial communities illustrates that groundwater salinization results in a more compact microbial network but enhances microbial interactions. Predicted functional genes indicate that sulfate reduction genes (sat, met3, aprA, aprB, dsrA, and dsrB) are more abundant in salty groundwater than in fresh groundwater, suggesting a high metabolic potential for sulfate. These results elucidate the pivotal role of groundwater salinization in microbial community evolution, shaping specific functional zones in coastal groundwater.

The Phylogeny and Metabolic Potentials of a Lignocellulosic Material-Degrading Aliiglaciecola Bacterium Isolated from Intertidal Seawater in East China Sea.

Lignocellulosic materials are composed of cellulose, hemicellulose and lignin and are one of the most abundant biopolymers in marine environments. The extent of the involvement of marine microorganisms in lignin degradation and their contribution to the oceanic carbon cycle remains elusive. In this study, a novel lignin-degrading bacterial strain, LCG003, was isolated from intertidal seawater in Lu Chao Harbor, East China Sea. Phylogenetically, strain LCG003 was affiliated with the genus Aliiglaciecola within the family Alteromonadaceae. Metabolically, strain LCG003 contains various extracellular (signal-fused) glycoside hydrolase genes and carbohydrate transporter genes and can grow with various carbohydrates as the sole carbon source, including glucose, fructose, sucrose, rhamnose, maltose, stachyose and cellulose. Moreover, strain LCG003 contains many genes of amino acid and oligopeptide transporters and extracellular peptidases and can grow with peptone as the sole carbon and nitrogen source, indicating a proteolytic lifestyle. Notably, strain LCG003 contains a gene of dyp-type peroxidase and strain-specific genes involved in the degradation of 4-hydroxy-benzoate and vanillate. We further confirmed that it can decolorize aniline blue and grow with lignin as the sole carbon source. Our results indicate that the Aliiglaciecola species can depolymerize and mineralize lignocellulosic materials and potentially play an important role in the marine carbon cycle.

Changes in the microbiome of the sea anemone Exaiptasia diaphana during bleaching from short-term thermal elevation

We examined the response of microbial communities in the model sea anemone Exaiptasia diaphana (Aiptasia) to short-term thermal elevation. Through 16S rRNA gene sequencing, we characterized the microbiomes of symbiotic (with algal symbionts) and aposymbiotic (bleached) anemones under ambient (27°C) and heat-stressed (34°C) conditions for 8-10 days, using both replicated endpoint and non-replicated time-course approaches. Consistent with prior studies, we observed a stable abundance of bacteria from the families Alteromonadaceae and Rhodobacteraceae, though with wide variation among individual anemones. We observed that symbiotic state conferred a larger impact on the microbiome than heat stress, implying the microbiome may play a metabolic role in the maintenance of cnidarian-dinoflagellate symbiosis. In particular, Pelobacter, an anaerobic sulfate reducer that is also a potential nitrogen fixer, was present only in symbiotic anemones, and its abundance decreased with initial exposure to 34°C, but recovered after 7 days. In aposymbiotic anemones, the added heat stress appeared to result in a large increase of rare bacterial taxa, which included potential pathogens such as Vibrio following bleaching. We also observed several archaea, the first reported for this model, but only in the seawater surrounding aposymbiotic Aiptasia, where abundance increased dramatically following heat stress. We further explored the diazotrophic (nitrogen fixation) potential of diverse bacteria associated with symbiotic and aposymbiotic Aiptasia, under both ambient and heat-stressed conditions, using nifH-PCR and qPCR and the acetylene reduction assay (ARA). In contrast to some stony corals, nifH was barely expressed in both anemone types, and under ambient conditions, diazotrophic activity was not detectable via ARA. Thus, although this research contributes to the growing knowledge of the bacterial community associated with a prominent model used in coral-symbiosis research, our results also suggest using caution when making direct comparisons between Aiptasia and different coral species in microbiome studies.

Bioprospecting for polyesterase activity relevant for PET degradation in marine Enterobacterales isolates.

Plastics have quickly become an integral part of modern life. Due to excessive production and improper waste disposal, they are recognized as contaminants present in practically all habitat types. Although there are several polymers, polyethylene terephthalate (PET) is of particular concern due to its abundance in the environment. There is a need for a solution that is both cost-effective and ecologically friendly to address this pollutant. The use of microbial depolymerizing enzymes could offer a biological avenue for plastic degradation, though the full potential of these enzymes is yet to be uncovered. The purpose of this study was to use (1) plate-based screening methods to investigate the plastic degradation potential of marine bacteria from the order Enterobacterales collected from various organismal and environmental sources, and (2) perform genome-based analysis to identify polyesterases potentially related to PET degradation. 126 bacterial isolates were obtained from the strain collection of RD3, Research Unit Marine Symbioses-GEOMAR-and sequentially tested for esterase and polyesterase activity, in combination here referred to as PETase-like activity. The results show that members of the microbial families Alteromonadaceae, Shewanellaceae, and Vibrionaceae, derived from marine sponges and bryozoans, are the most promising candidates within the order Enterobacterales. Furthermore, 389 putative hydrolases from the α/β superfamily were identified in 23 analyzed genomes, of which 22 were sequenced for this study. Several candidates showed similarities with known PETases, indicating underlying enzymatic potential within the order Enterobacterales for PET degradation.

Draft Genome Sequence of Aestuariibacter halophilus Type Strain JC2043.

ABSTRACTAestuariibacter halophilus strain JC2043, a Gram-negative gammaproteobacterium, is often used as a reference organism for assigning taxonomy within the family Alteromonadaceae. Isolates of this species have also been investigated for compound degradation (e.g., phthalates and oil) and biofilm association. Presented here is the draft genome sequence of A. halophilus strain JC2043.

Paraneptunicella aestuarii gen. nov., sp. nov., a member of the family Alteromonadaceae isolated from seawater in East China Sea.

An aerobic Gram-stain-negative, curved rod-shaped and non-spore-forming bacterial strain (NBU2194T) was isolated from seawater collected in an intertidal zone in Ningbo, Zhejiang Province, PR China. It was motile though a single polar flagellum and grew at 20-42 °C (optimum, 30 °C), in 0-2.0 % NaCl (0 %, w/v) and at pH 5.0-9.0 (pH 6.0-7.0). The sole respiratory quinone was ubiquinone-8. The major cellular fatty acids were C16 : 0, C16 : 1 ω7c and/or C16 : 1 ω6c. The polar lipids contained diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unidentified phospholipid and two unidentified aminophosphoglycolipids. A phylogenetic analysis based on 16S rRNA gene sequences and 65 genomic core genes showed that strain NBU2194T formed a distinct lineage in the family Alteromonadaceae. The genome of strain NBU2194T was 4 913 533 bp with a DNA G+C content of 43.9 mol% and coded 3895 genes, 12 rRNA genes and 47 tRNA genes. The average nucleotide identity, amino acid identity and digital DNA-DNA hybridization values between strain NBU2194T and related species of Alteromonadaceae were below the threshold limit for prokaryotic species delineation. NBU2194T could be distinguished from other genera in the family Alteromonadaceae based on phenotypic, chemotaxonomic and genomic characteristics. On the basis of the polyphasic taxonomic evidence collected in this study, strain NBU2194T is considered to represent a novel genus and species in the family Alteromonadaceae, for which the name Paraneptunicella aestuarii is proposed. The type strain is NBU2194T (=KCTC 82442T=GDMCC 1.2217T).

Development of a free radical scavenging bacterial consortium to mitigate oxidative stress in cnidarians.

SummaryCorals are colonized by symbiotic microorganisms that profoundly influence the animal’s health. One noted symbiont is a single‐celled alga (in the dinoflagellate family Symbiodiniaceae), which provides the coral with most of its fixed carbon. Thermal stress increases the production of reactive oxygen species (ROS) by Symbiodiniaceae during photosynthesis. ROS can both damage the algal symbiont’s photosynthetic machinery and inhibit its repair, causing a positive feedback loop for the toxic accumulation of ROS. If not scavenged by the antioxidant network, excess ROS may trigger a signaling cascade ending with the coral host and algal symbiont disassociating in a process known as bleaching. We use Exaiptasia diaphana as a model for corals and constructed a consortium comprised of E. diaphana–associated bacteria capable of neutralizing ROS. We identified six strains with high free radical scavenging (FRS) ability belonging to the families Alteromonadaceae, Rhodobacteraceae, Flavobacteriaceae and Micrococcaceae. In parallel, we established a consortium of low FRS isolates consisting of genetically related strains. Bacterial whole genome sequences were used to identify key pathways that are known to influence ROS.

Description of three new Alteromonas species Alteromonas antoniana sp. nov., Alteromonas lipotrueae sp. nov. and Alteromonas lipotrueiana sp. nov. isolated from marine environments, and proposal for reclassification of the genus Salinimonas as Alteromonas

In the course of a bioprospective study of marine prokaryotes for cosmetic purposes, four strains, MD_567T, MD_652T, MD_674 and PS_109T, were isolated that 16S rRNA gene affiliation indicated could represent three new species within the family Alteromonadaceae. A thorough phylogenetic, genomic and phenotypic taxonomic study confirmed that the isolates could be classified as three new taxa for which we propose the names Alteromonas antoniana sp. nov., Alteromonas lipotrueae sp. nov. and Alteromonas lipotrueiana sp. nov. In addition, the consistent monophyletic nature of the members of the genera Alteromonas and Salinimonas showed that both taxa should be unified, and therefore we also propose the reclassification of the genus Salinimonas within Alteromonas, as well as new combinations for the species of the former. As the specific epithets profundi and sediminis are already used for Alteromonas species, we created the nomina nova “Alteromonas alteriprofundi” nom. nov. and Alteromonas alterisediminis nom. nov. to accommodate the new names for “Salinimonas profundi” and Salinimonas sediminis. Whole genome comparisons also allowed us to detect the unexpected codification of aromatic hydrocarbon biodegradative compounds, such as benzoate and catechol, whose activity was then demonstrated phenotypically. Finally, the high genomic identity between the type strains of Alteromonas stellipolaris and Alteromonas addita indicated that the latter is a junior heterotypic synonym of Alteromonas stellipolaris.

Marinifaba aquimaris gen. nov., sp. nov., a novel chitin-degrading gammaproteobacterium in the family Alteromonadaceae isolated from seawater of the Mariana Trench.

A novel Gram-negative, rod-shaped, aerobic, oxidase-positive and catalase-negative bacterium, designated strain SM1970T, was isolated from a seawater sample collected from the Mariana Trench. Strain SM1970T grew at 15-37 oC and with 1-5% (w/v) NaCl. It hydrolyzed colloidal chitin, agar and casein but did not reduce nitrate to nitrite. Phylogenetic analysis based on the 16S rRNA gene sequences revealed that strain SM1970T formed a distinct lineage close to the genusCatenovulum within the familyAlteromonadaceae, sharing the highest sequence similarity (93.6%) with type strain ofCatenovulum maritimum but < 93.0% sequence similarity with those of other known species in the classGammaproteobacteria. The major fatty acids of strain SM1970T were summed feature 3 (C16: 1ω7c and/or C16: 1ω6c), C16: 0 and summed feature 8 (C18: 1ω7c and/or C18: 1ω6c). The major polar lipids of the strain included phosphatidylethanolamine and phosphatidylglycerol and its main respiratory quinone was ubiquinone 8. The draft genome of strain SM1970T consisted of 77 scaffolds and was 4,172,146bp in length, containing a complete set of genes for chitin degradation. The average amino acid identity (AAI) values between SM1970T and type strains of knownCatenovulum species were 56.6-57.1% while the percentage of conserved proteins (POCP) values between them were 28.5-31.5%. The genomic DNA G + C content of strain SM1970T was 40.1mol%. On the basis of the polyphasic analysis, strain SM1970T is considered to represent a novel species in a novel genus of the familyAlteromonadaceae, for which the nameMarinifaba aquimaris is proposed with the type strain being SM1970T (= MCCC 1K04323T = KCTC 72844T).

Marinobacter alexandrii sp. nov., a novel yellow-pigmented and algae growth-promoting bacterium isolated from marine phycosphere microbiota.

The marine phycosphere harbors unique cross-kingdom associations with ecological relevance. During investigating the diversity of phycosphere microbiota of marine harmful algal blooms dinoflagellates, a faint yellow-pigmented bacterium, designated as strain LZ-8, was isolated from paralytic shellfish poisoning toxin-producing dinoflagellate Alexandrium catenella LZT09. The new isolate appeared to have growth-promoting potential toward its algal host. Molecular analysis using 16S rRNA gene, housekeeping rpoD gene and whole-genome sequence comparison indicated that strain LZ-8T wasa novel gammaproteobacterium of the family Alteromonadaceae. The major fatty acids of strain LZ-8T were C16:0, C18:1 ω9c, C12:0 3-OH, summed feature 3, C16:1 ω9c, C12:0 and summed feature 9. The major isoprenoid quinone was Q-9. Polar lipids were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, unidentified phospholipid, two unidentified aminolipids and six unidentified polar lipids. The genomic DNA G+C content was 57.36mol%. Based on genome sequencing, several biosynthetic gene clusters responsible for bacterial biosynthesis of carotenoids and siderophores that may involve in algae-bacterial interactions were identified in the genome of strain LZ-8T. The polyphasic characterization indicated that strain LZ-8T represents a novel Marinobacter species. The name Marinobacter alexandrii sp. nov., type strain LZ-8T (= CCTCC AB 2018386T = KCTC 72198T) is proposed.

Algibacillus agarilyticus gen. nov., sp. nov., isolated from the surface of the red algae Gelidium amansii.

A novel Gram-stain-negative, strictly aerobic, coccoid and agar-hydrolysing bacterium, designated RQJ05T, was isolated from the marine red algae Gelidium amansii collected from the coastal area of Rizhao, PR China. Cells of strain RQJ05T were approximately 0.8-1.0×1.3-3.0 µm in size and motile by means of a polar flagellum. Growth occurred at 4-33 °C (optimum, 25-30 °C), pH 7.0-8.5 (optimum, pH 7.5-8.0) and in the presence of 1.0-7.0 % (w/v) NaCl (optimum, 2.0-3.0 %). Strain RQJ05T showed oxidase-positive and catalase-negative activities. Phylogenetic analysis based on 16S rRNA gene sequences indicated that strain RQJ05T formed a phylogenetic lineage with members of the family Alteromonadaceae and exhibited 16S rRNA gene sequence similarities of 92.6, 91.3, 90.2 and 90.1 % to Catenovulum maritimum Q1T, Catenovulum agarivorans YM01T, Paraphotobacterium marinum NSCS20N07DT and Algicola sagamiensis B-10-31T, respectively. The major cellular fatty acids of strain RQJ05T were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), C16 : 0 and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The major polar lipids of strain RQJ05T were phosphatidylethanolamine, phosphatidylglycerol and two aminophospholipids. Strain RQJ05T contained Q-8 as the major respiratory quinone. The genomic DNA G+C content was 39.0 mol%. On the basis of genotypic, phenotypic and phylogenetic evidence, strain RQJ05T is presented as a representative of a novel species in a new genus, for which the name Algibacillus agarilyticus gen. nov., sp. nov. is proposed. The type strain is RQJ05T (=KCTC 62846T=MCCC 1H00352T).

Microbial insights from Antarctic and Mediterranean shallow-water bone-eating worms

Bone-eating worms of the genus Osedax (Annelida, Siboglinidae) form unique holobionts (functional entity comprising host and associated microbiota), highly adapted to inhabit bone tissue of marine vertebrates. These gutless worms have developed nutritional symbioses housing intracellular, horizontally acquired, heterotrophic bacteria hypothesised to harness nutrients from organic compounds, sequestered within the bone. Despite previous efforts, critical mechanisms mediating activity and acquisition of diverse bacterial assemblages remain unclear. Using 16S rRNA amplicon sequencing, we performed detailed taxonomic and predicted functional analyses shedding light on the microbial communities of two shallow-water Osedax species (Osedax deceptionensis and Osedax ‘mediterranea’) from contrasting habitats (Antarctic and Mediterranean Sea), in two tissue types (roots and palps). Comparative assessments between host species revealed distinct microbial assemblages whilst, within host species and body tissue, relative symbiont frequencies retained high variability. We reported relatively high abundances of microbes previously classified as primary endosymbionts, Ribotype 1 (order Oceanospirillales), and diverse likely secondary epibionts warranting further exploration as recurrent Osedax associates. Surprisingly, O. ‘mediterranea’ exhibited relatively low abundance of Oceanospirillales, but increased abundance of other potentially hydrocarbon degrading bacteria from the family Alteromonadaceae. We hypothesise the presence of functionally similar, non-Oceanospirillales primary endosymbionts within O. ‘mediterranea’. Functional metagenomic profiling (using 16S rRNA sequences) predicted broad metabolic capabilities, encompassing relatively large abundances of genes associated with amino acid metabolism. Comparative analyses between host body tissue communities highlighted several genes potentially providing critical functions to the Osedax host or that confer adaptations for intracellular life, housed within bone embedded host root tissues.

Ningiella ruwaisensis gen. nov., sp. nov., a member of the family Alteromonadaceae isolated from marine water of the Arabian Gulf.

Strain B66T was isolated from a marine water sample collected at Al Ruwais, located on the northern tip of Qatar. Cells were Gram-stain-negative, strictly aerobic and short- rod-shaped with a polar flagellum. The isolate was able to grow at 15-45 °C (optimum, 30 °C), at pH 5-11 (optimum, pH 6.5-8) and with 0-6 % NaCl. 16S rRNA gene sequence analysis revealed that strain B66T was affiliated with the family Alteromonadaceae, sharing the highest sequence similarities to the genera Alteromonas (93.7-95.4 %), Aestuariibacter (94.0-95.1 %), Agaribacter (93.3-93.7 %), Glaciecola (92.0-93.7 %), Marisendiminitalea (93.2-93.3 %) and Planctobacterium (92.9 %). In the phylogenetic trees, strain B66T demonstrated the novel organism formed a distinct lineage closely associated with Aestuariibacter and Planctobacterium. Major fatty acids were C16 : 0, summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c/iso-C15 : 0 2-OH and iso-C15 : 0 3-OH. The major respiratory quinone was ubiquinone-8 and the major polar lipids are phosphatidylglycerol and phosphatidylethanolamine. The DNA G+C content derived from the genome was 43.2 mol%. Based on the phenotypic, chemotaxonomic, phylogenetic and genomic data, strain B66T is considered to represent a novel species and genus for which the name Ningiella ruwaisensis gen. nov., sp. nov., is proposed. The type strain is B66T (=QCC B003/17T=LMG 30288 T=CCUG 70703T).

Saliniradius amylolyticus gen. nov., sp. nov., isolated from solar saltern sediment.

A novel non-pigmented, Gram-stain-negative, motile by means of a polar flagellum, aerobic and rod-shaped bacterium, designated HMF8227T, was isolated from solar saltern sediment sampled at Shinan, Republic of Korea. The isolate was able to grow at 15-42 °C (optimum, 37 °C), at pH 6-8 (pH 7) and with 0.5-12 % NaCl (2-5 %). Strain HMF8227T was positive for hydrolysis of starch and dextrin. 16S rRNA gene sequence analysis revealed that strain HMF8227T was affiliated with the family Alteromonadaceae, sharing the highest sequence similarities to the genera Salinimonas (93.0-94.4 %), Aestuariibacter (92.0-94.2 %), Alteromonas (92.0-93.6 %) and Lacimicrobium (93.6 %). In the phylogenetic trees, strain HMF8227T formed an independent clade with Lacimicrobium alkaliphilum X13M-12T. The major fatty acids were C16 : 0, summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c) and summed feature 8 (C18 : 1 ω7c and/or C18 : 1 ω6c). The major respiratory quinone was ubiquinone-8 (Q-8). The major polar lipids are phosphatidylglycerol, phosphatidylethanolamine, one unidentified aminolipid and two unidentified glycolipids. The DNA G+C content of the genomic DNA was 52.1 mol%. On the basis of the polyphasic characterizations, strain HMF8227T represents a novel species and genus within the family Alteromonadaceae, for which the name Saliniradius amylolyticus gen. nov., sp. nov. is proposed, with the type strain being HMF8227T (=KCTC 62462T =NBRC 113230T).

Assessment of microbial dynamics and antioxidant enzyme gene expression following probiotic administration in farmed Pacific white shrimp (Litopenaeus vannamei)

The aims of this study were to explore the effect of a probiotic consortium at different concentrations (low, medium and high) on bacterial community structure and composition in the hepatopancreas and digestive tract of Pacific white shrimp Litopenaeus vannamei reared under superintensive conditions, as well as to investigate its effect on gene expression of antioxidant enzymes. After the 69-day experimental period, shrimp treated with high probiotic concentration showed higher final growth, specific growth rate, weight gain and survival (p < .05) than those treated with low probiotic concentration or without probiotics; however, there were no significant differences compared to those treated with medium probiotic concentration. The analysis of the bacterial community structure revealed significant differences among treatments with and without probiotics; however, there were no differences between hepatopancreas and digestive tract samples, independently of the treatment received. Moreover, there were no differences in those samples from shrimp treated with probiotics at medium and high concentrations. The analysis of the bacterial community composition showed a higher proportion of Alphaproteobacteria (particularly members belonging to the family Rhodobacteraceae) in hepatopancreas and digestive tract samples from shrimp treated with probiotics at medium and high concentrations than in those treated with low probiotic concentration or without probiotics. In contrast, a higher proportion of Gammaproteobacteria (particularly members belonging to the families Alteromonadaceae, Moraxellaceae, Pseudomonadaceae and Vibrionaceae) was found in both sample types from shrimp treated without probiotics than in those treated with probiotics, independently of the concentration tested. At the end of the study, the levels of MnSOD (manganese superoxide dismutase) and CAT (catalase) transcripts were similar among hepatopancreas samples from shrimp treated with or without probiotics; however, the levels of GPx (glutathione peroxidase) transcripts drastically increased in those samples from shrimp treated without probiotics. These results could explain, in part, the mechanisms (i.e., competitive exclusion and immunomodulation) whereby probiotics confer beneficial effects to the host.

Marinobacter vulgaris sp. nov., a moderately halophilic bacterium isolated from a marine solar saltern.

A facultatively anaerobic, Gram-stain-negative and non-gliding bacterium, designated F01T, was isolated from marine solar saltern in Weihai, PR China. Cells of F01T were 0.2-0.4 µm wide and 1.4-4.1 µm long, weakly catalase-positive and oxidase-negative. Growth of F01T was determined to occur at 4-40 °C (optimum, 33-37 °C), pH 6.5-8.5 (optimum, 7.0-8.0), and with 0.5-18.0 % (w/v) NaCl (optimum, 3.0-6.0 %). The 16S rRNA gene sequence analysis indicated that F01T represented a member of the genus Marinobacter within the family Alteromonadaceae. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the isolate was most closely related to Marinobacter algicola DSM 16394T, with a sequence similarity of 97.5 %. The DNA G+C content of the isolate was 57.6 mol%. The major respiratory quinone of F01T was ubiquinone-9 (Q-9) and the major fatty acids were anteiso-C15 : 0, C16 : 0 and C18 : 1ω9c. The major polar lipids were phosphoaminolipid, phosphatidylglycerol and phosphatidylethanolamine. On the basis of the results of the phylogenetic analysis and phenotypic properties, it is concluded that F01T can be considered to represent a novel species in the genus Marinobacter, for which the name Marinobacter vulgaris sp. nov. is proposed. The type strain is F01T (=MCCC 1H00290T=KCTC 52700T).

Alteromonas fortis sp. nov., a non-flagellated bacterium specialized in the degradation of iota-carrageenan, and emended description of the genus Alteromonas.

Strain 1T, isolated in the 1970s from the thallus of the carrageenophytic red algae, Eucheuma spinosum, collected in Hawaii, USA, was characterized using a polyphasic method. Cells were Gram-stain-negative, strictly aerobic, non-flagellated, ovoid or rod-shaped and grew optimally at 20-25 °C, at pH 6-9 and with 2-4 % NaCl. Strain 1T used the seaweed polysaccharides ι-carrageenan, laminarin and alginic acid as sole carbon sources. The major fatty acids were C16 : 0, C18 : 1 ω7c and summed feature 3 (C16 : 1 ω7c and/or iso-C15 : 0 2OH) with significant amounts (>6 %) of C16 : 0 N alcohol and 10 methyl C17 : 0. The respiratory quinone was Q-8 and major polar lipids were phosphatidylethanolamine, phosphatidylglycerol and an unknown aminolipid. Phylogenetic analyses showed that the bacterium is affiliated to the genus Alteromonas (family Alteromonadaceae, class Gammaproteobacteria). Strain 1T exhibited 16S rRNA gene sequence similarity values of 98.8 and 99.2 % to the type strains of Alteromonas mediterranea and Alteromonas australica respectively, and of 95.2-98.6 % to other species of the genus Alteromonas. The DNA G+C content of strain 1T was determined to be 43.9 mol%. Digital DNA-DNA hybridization predictions by the ANI and GGDC methods between strain 1T and other members of the genus Alteromonas showed values below 83 % and 30 %, respectively. The phenotypic, phylogenetic and genomic analyses show that strain 1T is distinct from species of the genus Alteromonas with validly published names and that it represents a novel species of the genus Alteromonas, for which the name Alteromonasfortis sp. nov. is proposed. The type strain is 1T (=ATCC 43554T=RCC 5933T=CIP 111645T=DSM 106819T).

Hydrocarboniclastica marina gen. nov., sp. nov., a marine hydrocarbonoclastic bacterium isolated from an in situ enriched hydrocarbon-degrading consortium in sea sediment.

A Gram-stain-negative, motile, non-spore-forming, aerobic and rod-shaped bacterial strain, Soil36-7T, was isolated from an in situ enriched hydrocarbon-degrading consortium in South China Sea sediment. Strain Soil36-7T grew at 4-40 °C (optimum 28-32 °C), at pH 5-10 (pH 7-8) and in the presence of 1-12 % (w/v) NaCl (3-6 %). Phylogenetic analyses based on 16S rRNA gene sequences and a genome-based approach using UBCGs (up-to-date bacterial core genes) showed Soil36-7T formed a distinct branching lineage within the family Alteromonadaceae. 16S rRNA gene sequence similarity was 92.9, 92.1 and >88.3 % between strain Soil36-7T and the type species of the genera Marinobacter, Tamilnaduibacter and the other genera of the family Alteromonadaceae, respectively. The major fatty acids in Soil36-7T were C16 : 0, C16 : 1ω6/7c, C16 : 0 10-methyl, C18 : 1ω7c, C12 : 0 and C18 : 0. The predominant respiratory quinone was Q-9, with a minor amount of Q-10 (3.5 %). The major polar lipids were phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol, phosphatidylinositol, and various unidentified glycolipids, phospholipids, aminophospholipids and other polar lipids. The DNA G+C content was 57.9 mol%. On the basis of phylogenetic, genomic, phenotypic and chemotaxanomic characteristics, strain Soil36-7T could be classified as representing a novel species of a new genus within the family Alteromonadaceae, for which the name Hydrocarboniclastica marina gen. nov., sp. nov. is proposed. The type strain of the type species is Soil36-7T (=MCCC 1A12105T=KCTC 62334T).

Biodegradation of polyamide 4 in seawater

Herein, we report on the aquatic degradation of polyamide (nylon) 4. Polyamide 4 (PA4) has previously been shown to degrade in natural environments such as activated sludge and soil, as well as in vivo (when subcutaneously implanted in the backs of rats). In laboratory biodegradation tests of PA4, polyhydroxybutyrate (PHB), and polycaprolactone (PCL) in sampled seawater, the amount of oxygen absorption increased over time. PA4 degraded by about 30% in 4 weeks, which is comparable to that of PCL (30%) but less than that of PHB (60%). PA4 films were immersed in the sea and recovered at adequate intervals and weighed. The weight of the films decreased by 10–70% in 6 weeks, showing that PA4 is degraded in actual aquatic (sea) environments. We isolated PA4-degrading bacteria, strain MND-1, from the seawater used in the laboratory degradation tests. MND-1 is thought to belong to the family Alteromonadaceae from the DNA sequence of 16S rDNA. Gamma-aminobutyric acid (GABA) and GABA oligomers were detected in the PA4 degradation products. This indicates that the strain MND-1 hydrolyzes the amide bonds of PA4 into GABA oligomers and GABA.

Characterizing microbial diversity and community composition of groundwater in a salt-freshwater transition zone

A salt-freshwater transition zone due to seawater intrusion to groundwater promotes changes in microbial diversity and community composition in a coastal aquifer. The main purpose of this study is to explore the effect of seawater intrusion on the groundwater quality in a salt-freshwater transition zone and identify the microbial fingerprints of seawater intrusion. The changes in microbial community diversity response to the seawater intrusion were characterized by comparing the community structures of the microbes in fresh groundwater, seawater, and salty groundwater from various monitoring wells at different depths using the high throughput 16S rDNA gene sequencing. Results show that seawater had the lowest taxon richness and evenness, and the irrigation water had the highest richness and evenness. Statistical analysis showed that DO%, ORP, and Cl− affected microbial distribution in the groundwater; while DO% was a main environmental factor influencing microbial community diversity. The analysis of microbial community structures indicates that the order Oceanospirillales and the family Alteromonadaceae could be used as indicators of seawater intrusion.