The proliferation/migration ability mediated by CD151/PI3K/AKT pathway determines the therapeutic effect of hUC-MSCs transplantation on rheumatoid arthritis.

OBJECTIVE: To elucidate the underlying mechanism by which the proliferation and migration abilities of human umbilical cord mesenchymal stem cells (hUC-MSCs) determine their therapeutic efficacy in rheumatoid arthritis treatment. METHODS: The DBA/1J mice were utilized to establish a collagen-induced RA (CIA) mouse model and to validate the therapeutic efficacy of hUC-MSCs transfected with CD151 siRNA. RNA-seq, QT-PCR and western blotting were utilized to evaluate the mRNA and protein levels of the PI3K/AKT pathway, respectively. RESULTS: IFN-γ significantly enhanced the proliferation and migration abilities of hUC-MSCs, up-regulating the expression of CD151, a gene related to cell proliferation and migration. Effective inhibition of this effect was achieved through CD151 siRNA treatment. However, IFN-γ did not affect hUC-MSCs differentiation or changes in cell surface markers. Additionally, transplantation of CD151-interfered hUC-MSCs (siRNA-CD151-hUC-MSCs) resulted in decreased colonization in the toes of CIA mice and worse therapeutic effects compared to empty vector treatment (siRNA-NC-hUC-MSCs). CONCLUSION: IFN-γ facilitates the proliferation and migration of hUC-MSCs through the CD151/PI3K/AKT pathway. The therapeutic efficacy of siRNA-CD151-hUC-MSCs was found to be inferior to that of siRNA-NC-hUC-MSCs.

Hwangdonia lutea sp. nov., isolated from the Haima cold seep, South China Sea.

A Gram-stain-negative, orange-yellow, rod-shaped bacterium, designated strain SCSIO 19198T, was isolated from sediment of the Haima cold seep in the South China Sea, PR China. The strain was aerobic and non-motile. Growth of strain SCSIO 19198T occurred at pH 7-9 (optimum, pH 7), 15-37 °C (optimum, 25-32 °C) and with 3-8 % (w/v) NaCl (optimum, 3-6 % NaCl). Phylogenetic analyses based on 16S rRNA sequences revealed that strain SCSIO 19198T belonged to the genus Hwangdonia, having the highest similarity to Hwangdonia seohaensis HD-3T (98.35 %), followed by Algibacter aquimarinus KYW589T (95.17 %) and Gelatiniphilus marinus GYP-24T (94.89 %). The DNA G+C content was 35.92 mol%. The average nucleotide identity value between the genome of strain SCSIO 19198T and that of H. seohaensis HD-3T was 88.49 %. The digital DNA-DNA hybridization value between strain SCSIO 19198T and H. seohaensis HD-3T was 36 %. The major fatty acids (>10 %) of strain SCSIO 19198T were iso-C15 : 0, iso-C15 : 1 G, summed feature 3 (C16 : 1 ω6c/C16 : 1 ω7c) and anteiso-C15 : 0. MK-6 was the only detected respiratory quinone. The polar lipids of strain SCSIO 19198T included phosphatidylethanolamine, two aminolipids, glycolipid and two unidentified lipids. The phenotypic, phylogenetic, chemotaxonomic and genomic data clearly suggest that strain SCSIO 19198T represents a novel species of the genus Hwangdonia, for which the name Hwangdonia lutea sp. nov. is proposed. The type strain is SCSIO 19198T (=MCCC 1K08674T=KCTC 102078T).

Biocrust reduces the soil erodibility of coral calcareous sand by regulating microbial community and extracellular polymeric substances on tropical coral island, South China Sea.

Tropical coral islands assume a pivotal role in the conservation of oceanic ecosystem biodiversity. However, their distinctive environmental attributes and limited vegetation render them highly susceptible to soil erosion. The biological soil crust (biocrust), owing to its significant ecological role in soil stabilization and erosion prevention, is deemed an effective means of mitigating soil erosion on coral island. However, existing research on the mechanisms through which biocrusts resist soil erosion has predominantly concentrated on arid and semi-arid regions. Consequently, this study will specifically delve into elucidating the erosion-resistant mechanisms of biocrusts in tropical coral island environments, South China Sea. Specifically, we collected 16 samples of biocrusts and bare soil from Meiji Island. High-throughput amplicon sequencing was executed to analyze the microbial community, including bacteria, fungi, and archaea. Additionally, quantitative PCR was utilized to assess the abundance of the bacterial 16S rRNA, fungal ITS, archaeal 16S rRNA, and cyanobacterial 16S rRNA genes within these samples. Physicochemical measurements and assessments of extracellular polymeric substances (EPSs) were conducted to characterize the soil properties. The study reported a significantly decreased soil erodibility factor after biocrust formation. Compared to bare soil, soil erodibility factor decreased from 0.280 to 0.190 t h MJ-1 mm-1 in the biocrusts. Mechanistically, we measured the microbial EPS contents and revealed a negative correlation between EPS and soil erodibility factor. Consistent with increased EPS, the abundance of bacteria, fungi, archaea, and cyanobacteria were also detected significantly increased with biocrust formation. Correlation analysis detected Cyanobacteria, Chloroflexi, Deinococcota, and Crenarchaeota as potential microbials promoting EPSs and reducing soil erosion. Together, our study presents the evidence that biocrust from tropical coral island in the South China Sea promotes resistance to soil erosion, pinpointing key EPSs-producing microbials against soil erosion. The findings would provide insights for island soil restoration.

Radial Oxygen Loss from the Roots of Mangrove Seedlings Enhances the Removal of Polycyclic Aromatic Hydrocarbons.

The presence of polycyclic aromatic hydrocarbons (PAHs) in soil poses a significant global environmental concern, particularly in coastal wetlands. Mangrove ecosystems exhibit enormous potential in environmental purification; however, the underlying mechanisms involved in the degradation of pollutants (e.g., PAHs) remain ambiguous. In the present investigation, a soil pot experiment was conducted with the addition of pyrene to evaluate the effect of radial oxygen loss (ROL) from roots on PAH degradation using three mangrove seedlings (Rhizophora stylosa, Aegiceras corniculatum, and Avicennia marina). The results showed that mangrove plantation can significantly promote the efficiency of pyrene removal. As for the three mangrove species studied, the greatest removal rate (90.75%) was observed in the soils associated with A. marina, followed by A. corniculatum (83.83%) and R. stylosa (77.15%). The higher PAH removal efficiency of A. marina can be partially attributed to its distinctive root anatomical structure, characterized by a thin exodermis and high porosity, which facilitates ROL from the roots. The results from qPCR further demonstrate that ROL is beneficial for promoting the abundance of PAH-ring hydroxylating dioxygenase gene, leading to a higher removal efficiency. Additionally, Rhizobiales, Defferrisomatales, and Ardenticatenales may also play important roles in the process of pyrene degradation. In summary, this study provides evidence for elucidating the mechanism of PAH removal from the perspective of ROL, thereby contributing valuable insights for species selection during mangrove restoration and remediation.

Environmental heterogeneity shapes the C and S cycling-associated microbial community in Haima's cold seeps.

Environmental heterogeneity in cold seeps is usually reflected by different faunal aggregates. The sediment microbiome, especially the geochemical cycling-associated communities, sustains the ecosystem through chemosynthesis. To date, few studies have paid attention to the structuring and functioning of geochemical cycling-associated communities relating to environmental heterogeneity in different faunal aggregates of cold seeps. In this study, we profiled the microbial community of four faunal aggregates in the Haima cold seep, South China Sea. Through a combination of geochemical and meta-omics approaches, we have found that geochemical variables, such as sulfate and calcium, exhibited a significant variation between different aggregates, indicating changes in the methane flux. Anaerobic methanotrophic archaea (ANME), sulfate-reducing, and sulfide-oxidizing bacteria (SRB and SOB) dominated the microbial community but varied in composition among the four aggregates. The diversity of archaea and bacteria exhibited a strong correlation between sulfate, calcium, and silicate. Interspecies co-exclusion inferred by molecular ecological network analysis increased from non-seep to clam aggregates and peaked at the mussel aggregate. The networked geochemical cycling-associated species showed an obvious aggregate-specific distribution pattern. Notably, hydrocarbon oxidation and sulfate reduction by ANME and SRB produced carbonate and sulfide, driving the alkalization of the sediment environment, which may impact the microbial communities. Collectively, these results highlighted that geofluid and microbial metabolism together resulted in environmental heterogeneity, which shaped the C and S cycling-associated microbial community.

Chlorinated Paraffin Pollution in the Marine Environment.

Chlorinated paraffins (CPs) are ubiquitous in the environment due to their large-scale usage, persistence, and long-range atmospheric transport. The oceans are a critical environment where CPs transformation occurs. However, the broad impacts of CPs on the marine environment remain unclear. This review describes the sources, occurrence and transport pathways, environmental processes, and ecological effects of CPs in the marine environment. CPs are distributed in the global marine environment by riverine input, ocean currents, and long-range atmospheric transport from industrial areas. Environmental processes, such as the deposition of particle-bound compounds, leaching of plastics, and microbial degradation of CPs, are the critical drivers for regulating CPs' fate in water columns or sediment. Bioaccumulation and trophic transfer of CPs in marine food webs may threaten marine ecosystem functions. To elucidate the biogeochemical processes and environmental impacts of CPs in marine environments, future work should clarify the burden and transformation process of CPs and reveal their ecological effects. The results would help readers clarify the current research status and future research directions of CPs in the marine environment and provide the scientific basis and theoretical foundations for the government to assess marine ecological risks of CPs and to make policies for pollution prevention and control.

Identification and yield of metabolites of chlorinated paraffins incubated with chicken liver microsomes: Assessment of their potential to convert into metabolites.

Chlorinated paraffins (CPs) are emerging environmental pollutants. Although metabolism has been shown to affect the differential accumulation of short-chain (SCCPs), medium-chain (MCCPs) and long-chain (LCCPs) CPs in birds, CP metabolites have rarely been reported and the extent to which they are formed is still unclear. In this study, single and mixed CP standards were incubated with chicken liver microsomes in vitro to study the generation of CP metabolites. Putative aldehyde/ketone and carboxylic acid metabolites identified by mass spectroscopy data were shown to be false positive results. Phase I metabolism of CPs first formed monohydroxylated ([M-Cl+OH]) and then dihydroxylated ([M-2Cl+2OH]) products. The yields of monohydroxylated metabolites of CPs decreased with increasing carbon chain length and chlorine content at the initial stage of reaction. Notably, the yield of monohydroxylated metabolites of SCCPs with 51.5% Cl content reached 21%, and that of 1,2,5,6,9,10-hexachlorodecane (C10H16Cl6) was as high as 71%. Thus, monohydroxy metabolites of CPs in birds should not be ignored, especially those of SCCPs. This study provides important data that could support improvements to the ecological/health risk assessment of CPs.

Bioaccumulation of emerging persistent organic pollutants in the deep-sea cold seep ecosystems: Evidence from chlorinated paraffin.

Persistent organic pollutants (POPs) are highly toxic and can accumulate in marine organisms, causing nonnegligible harm to the global marine ecosystem. The Cold seep is an essential marine ecosystem with the critical ecological function of maintaining the deep-sea carbon cycle and buffering global climate change. However, the environmental impact of emerging POPs in the deep-sea cold seep ecosystem is unknown. Here, we investigated the potential pollution of chlorinated paraffins (CPs) and their bioaccumulation in the cold seep ecosystem. High concentrations of CPs were detected in the cold seep ecosystems, where CPs bioaccumulated by the keystone species of deep-sea mussels can be released into the surface sediment and vertically migrate into the deeper sediment. Furthermore, more toxic CPs were accumulated from transforming other CPs in the cold seep ecosystem. Our study provides the first evidence that high concentrations of POPs are bioaccumulated by deep-sea mussels in the cold seep ecosystem, causing adverse ecological effects. The discovery of CPs bioaccumulation in the deep-sea cold seep ecosystem is a crucial mechanism affecting deep-sea carbon transport and cycling. This study has important guiding significance for revealing the deep-sea carbon cycle process, addressing global climate change, and making deep-sea ecological and environmental protection policies.

Riddles of Lost City: Chemotrophic Prokaryotes Drives Carbon, Sulfur, and Nitrogen Cycling at an Extinct Cold Seep, South China Sea.

Deep-sea cold seeps are one of the most productive ecosystems that sustained by hydrocarbons carried by the fluid. Once the seep fluid ceases, the thriving autotrophic communities die out, terming as the extinct seep. But heterotrophic fauna can still survive even for thousands of years. The critical role of prokaryotes in active seeps are well defined, but their functions in extinct seeps are poorly understood to date. Here, we clarified the diversity, taxonomic specificity, interspecies correlation, and metabolic profiles of sediment prokaryotes at an extinct seep site of Haima cold seep, South China Sea. Alpha diversity of archaea significantly increased, while that of bacteria remained unchanged in extinct seep compared to active seep. However, archaea composition did not differ significantly at extinct seep from active or nonseep sites based on weighted-unifrac dissimilarity, while bacteria composition exhibited significant difference. Distribution of archaea and bacteria showed clear specificity to extinct seeps, indicating the unique life strategies here. Prokaryotes might live chemolithoautotrophically on cycling of inorganic carbon, sulfur, and nitrogen, or chemoorganotrophically on recycling of hydrocarbons. Notably, many of the extinct seep specific species and networked keystone lineages are classified as Proteobacteria. Regarding the functional diversity and metabolic flexibility of this clade, Proteobacteria is supposed to integrate the geochemical cycles and play a critical role in energy and resource supplement for microbiome in extinct seep. Collectively, our findings shed lights on the microbial ecology and functional diversity in extinct seeps, providing new understanding of biogeochemical cycling after fluid cessation. IMPORTANCE This research paper uncovered the potential mechanisms for microbiota mediated geochemical cycling in extinct cold seep, advancing our understanding in deep sea microbiology ecology.

Degradation potential of alkanes by diverse oil-degrading bacteria from deep-sea sediments of Haima cold seep areas, South China Sea.

Marine oil spills are a significant concern worldwide, destroying the ecological environment and threatening the survival of marine life. Various oil-degrading bacteria have been widely reported in marine environments in response to marine oil pollution. However, little information is known about culturable oil-degrading bacteria in cold seep of the deep-sea environments, which are rich in hydrocarbons. This study enriched five oil-degrading consortia from sediments collected from the Haima cold seep areas of the South China Sea. Parvibaculum, Erythrobacter, Acinetobacter, Alcanivorax, Pseudomonas, Marinobacter, Halomonas, and Idiomarina were the dominant genera. Further results of bacterial growth and degradation ability tests indicated seven efficient alkane-degrading bacteria belonging to Acinetobacter, Alcanivorax, Kangiella, Limimaricola, Marinobacter, Flavobacterium, and Paracoccus, whose degradation rates were higher in crude oil (70.3-78.0%) than that in diesel oil (62.7-66.3%). From the view of carbon chain length, alkane degradation rates were medium chains > long chains > short chains. In addition, Kangiella aquimarina F7, Acinetobacter venetianus F1, Limimaricola variabilis F8, Marinobacter nauticus J5, Flavobacterium sediminis N3, and Paracoccus sediminilitoris N6 were first identified as oil-degrading bacteria from deep-sea environments. This study will provide insight into the bacterial community structures and oil-degrading bacterial diversity in the Haima cold seep areas, South China Sea, and offer bacterial resources to oil bioremediation applications.

Pelagibacterium xiamenense sp. nov., isolated from intertidal sediment.

A Gram-stain-negative, obligately aerobic bacterium, designated as HS1C4-1T, was isolated from a sediment sample from the tidal zone of the Haicang Coast, Xiamen, Fujian Province, PR China. The strain was yellowish-coloured, non-gliding, rod-shaped and motile, with a single polar flagellum. Cells of HS1C4-1T were oxidase- and catalase-positive. The strain could grow at 15-55 °C (optimum 37 °C), pH 6.0-10.0 (optimum, pH 7.0-9.0), in the presence of 0-12 % (optimum, 1 %) NaCl (w/v). Phylogenetic analysis based on the 16S rRNA gene sequences indicated that HS1C4-1T represented a member of the genus Pelagibacterium, and shared the highest similarity to Pelagibacterium luteolum CGMCC 1.10267T (97.6 %). Digital DNA-DNA hybridization values and average nucleotide identity between HS1C4-1T and all the species of genus Pelagibacterium were 18.7-20.2 % and 77.3-78.4 %, respectively. The principal fatty acids (>10 %) were C19 : 0 cyclo ω8c (50.5 %) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c; 29.1%). Q-10 was the sole respiratory quinone. The polar lipids included diphosphatidylglycerol, phosphatidylglycerol, two unidentified glycolipids and six unidentified lipids. The G+C content of the chromosomal DNA was 62.9 %. On the basis of phylogenetic, phenotypic, chemotaxonomic and genomic characteristics, HS1C4-1T represents a novel species within the genus Pelagibacterium, for which the name Pelagibacterium xiamenense sp. nov. is proposed. The type strain is HS1C4-1T (=MCCC 1A18759T=KCTC 92097T).

Characterization of chlorinated paraffin-degrading bacteria from marine estuarine sediments.

This study explored chlorinated paraffin (CP)-degrading bacteria from the marine environment. Aequorivita, Denitromonas, Parvibaculum, Pseudomonas and Ignavibacterium were selected as the dominant genera after enrichment with chlorinated paraffin 52 (CP52) as the sole carbon source. Eight strains were identified as CP degraders, including Pseudomonas sp. NG6 and NF2, Erythrobacter sp. NG3, Castellaniella sp. NF6, Kordiimonas sp. NE3, Zunongwangia sp. NF12, Zunongwangia sp. NH1 and Chryseoglobus sp. NF13, and their degradation efficiencies ranged from 6.4% to 19.0%. In addition to Pseudomonas, the other six genera of bacteria were first reported to have the degradation ability of CPs. Bacterial categories, carbon-chain lengths and chlorination degrees were three crucial factors affecting the degradation efficiencies of CPs, with their influential ability of chlorinated degrees > bacterial categories > carbon-chain lengths. CP degradation can be performed by producing chlorinated alcohols, chlorinated olefins, dechlorinated alcohols and lower chlorinated CPs. This study will provide valuable information on CP biotransformation and targeted bacterial resources for studying the transformation processes of specific CPs in marine environments.

Annual hypoxia causing long-term seawater acidification: Evidence from low-molecular-weight organic acids in the Changjiang Estuary and its adjacent sea area.

In this study, components, concentrations, distribution characteristics, sources of low-molecular-weight organic acids (LMWOAs) and relationships among the annual hypoxia, LMWOAs and seawater acidification were investigated in the Changjiang Estuary and its adjacent sea area in July 2015. Lactic, acetic and formic acids were detected in the seawater samples in the study area, and their total concentrations (ΣLMWOAs) varied from 0 to 262.6 µmol·L-1, with an average value of 39.2 µmol·L-1. In the surface seawater, high concentration areas of ΣLMWOAs occurred in the sea area near the Changjiang Estuary and the Hangzhou Bay, and north of study area. In the sampling stations along transect A6, high concentration areas of ΣLMWOAs appeared in the bottom seawater of nearshore stations and middle seawater of offshore stations. The terrigenous inputs, especially the Changjiang runoff, were the dominant sources for LMWOAs in the sampling period. The consistency of hypoxia areas, high concentration areas of ΣLMWOAs and low pH value areas in winter and summer suggested that annual hypoxia could cause the long-term seawater acidification by producing LMWOAs in the Changjiang Estuary and its adjacent sea area.

Gordonia tangerina sp. nov., isolated from seawater.

A Gram-stain-positive, aerobic bacterium, designated GW1C4-4T, was isolated from the seawater sample from the tidal zone of Guanyinshan Coast, Xiamen, Fujian Province, PR China. The strain was reddish-orange, rod-shaped and non-motile. Cells of strain GW1C4-4T were oxidase-negative and catalase-positive. The strain could grow at 10-42 °C (optimum, 32-35 °C), pH 5-9 (optimum, pH 6) and with 0-10 % NaCl (w/v; optimum, 1 %). Phylogenetic analysis based on the 16S rRNA sequences indicated that strain GW1C4-4T belonged to the genus Gordonia, having the highest similarity to Gordonia mangrovi HNM0687T (98.5 %), followed by Gordonia bronchialis DSM 43247T (98.4 %). The G+C DNA content was 66.5 mol %. Average nucleotide identity and digital DNA-DNA hybridization values between strain GW1C4-4T and G. mangrovi HNM0687T were 85.8 and 30.0 %, respectively. The principal fatty acids of strain GW1C4-4T were C16 : 0, C18 : 0 10-methyl (TBSA) and summed feature 3 (C16 : 1 ω7c/C16 : 1 ω6c). MK-9 (H2) was the sole respiratory quinone. The polar lipids included diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine and an unidentified lipid. Based on its phylogenetic, phenotypic, chemotaxonomic and genomic characteristics, it is proposed that strain GW1C4-4T represents a novel species within the genus Gordonia, for which the name Gordonia tangerina sp. nov. is proposed. The type strain is GW1C4-4T (=MCCC 1A18727T=KCTC 49729T).

Distribution characteristics of low molecular weight organic acids in seawater of the Changjiang Estuary and its adjacent East China Sea: Implications for regional environmental conditions.

In this study, components, concentrations, distribution characteristics and sources of low molecular weight organic acids (LMWOAs) in seawater of the Changjiang Estuary and its adjacent East China Sea were investigated in March 2015. Lactic, acetic and formic acids were identified with their concentration range of 0-16.7, 0-42.7 and 0-6.7 µmol·L-1, respectively. In the surface seawater, high concentrations of LMWOAs appeared in the sea area close to the estuary and along the coast. LMWOAs were important fractions of dissolved organic carbon and acetic acid was dominant component of LMWOAs. Riverine, terrestrial input, phytoplankton and sediment release were important sources for the LMWOAs, and human activities were considered as dominant sources for them in sampling period. The consistency of regions with high concentrations of LMWOAs, eutrophication, seasonal hypoxia and frequent red tide occurrence suggested LMWOAs as potential indicators for evaluating pollution status in coastal areas.

Paracoccus xiamenensis sp. nov., isolated from seawater on the Xiamen.

Strain 12-3T was isolated from seawater of the Guanyinshan Coast, Xiamen, Fujian Province, PR China. The bacterium was Gram-stain-negative, rod-shaped, aerobic, oxidase-positive and catalase-negative. Growth of strain 12-3T occurred at 10-37 °C (optimum, 20-30 °C), at pH 5.0-11.0 (optimum, pH 7.0-8.0) and at a salinity range of 0-10 % (optimum, 3-5 %). The results of phylogenetic analysis based on its 16S rRNA gene sequence indicated that strain 12-3T belonged to the genus Paracoccus and had the highest sequence similarity to Paracoccus lutimaris HDM-25T (97.4 %), followed by Paracoccus isoporae SW-3T (96.9 %), Paracoccus caeni MJ17T (96.9 %), Paracoccus pacificus F14T (96.8 %) and other species in the genus Paracoccus (95.3-96.5 %). The average nucleotide identity (ANI) and DNA-DNA hybridization (DDH) values between strain 12-3T and P. lutimaris HDM-25T were 76.1 and 17.0 %, respectively. ANI and DDH values between strain 12-3T and P. isoporae SW-3T were 78.9 and 18.2 %, respectively. The principal fatty acid of strain 12-3T was summed feature 8 (C18 : 1 ω6c/ω7c) and C18 : 0. The respiratory quinone of strain 12-3T was Q10. The polar lipids included phosphatidylcholine, phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol and an unidentified glycolipid. The G+C content of the chromosomal DNA was 63.9 mol%. The combination of the results of the phylogenetic, phenotypic and chemotaxonomic analyses, and its low ANI and DDH values indicate that strain 12-3T represents a novel species of the genus Paracoccus, for which the name Paracoccus xiamenensis sp. nov. is proposed. The type strain is 12-3T (=MCCC 1A16381T=KCTC 72687T).

Pseudooceanicola pacificus sp. nov., isolated from deep-sea sediment of the Pacific Ocean.

A Gram-strain-negative, rod-shaped, aerobic bacterium, designated 216_PA32_1T, was isolated from deep-sea sediment of the Pacific Ocean. Cells of strain 216_PA32_1T were non-motile, oxidase-positive and catalase-negative. The strain could grow at temperatures of 10-45 °C (optimum, 32-35 °C), at pH 5.0-10.0 (optimum, 6.0-7.0) and at salinities of 0-10% (optimum, 2-8%). The principal fatty acid (>10 %) was summed feature 8 (C18:1 ω6c/ω7c). The sole respiratory quinone was Q10 (100 %). The polar lipids included phosphatidylethanolamine, phosphatidylcholine, phosphatidylglycerol, phosphatidylmonomethylethanolamine, two unidentified phospholipids and five unidentified aminolipids. The G+C content of the chromosomal DNA was 66.3 mol%. According to the 16S rRNA gene similarity, strain 216_PA32_1T showed the highest sequence similarity to Pseudooceanicola nitratireducens JLT 1210T (97.3 %), followed by Pseudooceanicola nanhaiensis SS011B1-20T (97.1 %). Phylogenetic trees indicated that strain 216_PA32_1T clustered with strain P. nanhaiensis SS011B1-20T. The average nucleotide identity and the DNA-DNA hybridization values between strain 216_PA32_1T and all species of the genus Pseudooceanicola were below 79.5 and 20.6%, respectively. A combination of the phylogenetic, phenotypic, chemotaxonomic and genomic evidence demonstrated that strain 216_PA32_1T represents a novel species of the genus Pseudooceanicola, for which the name Pseudooceanicola pacificus sp. nov. is proposed. The type strain is 216_PA32_1T (=MCCC 1A14128T=KCTC 72688T).

Low-molecular-weight organic acids as important factors impacting seawater acidification: A case study in the Jiaozhou Bay, China.

Low-molecular-weight organic acids (LMWOAs) are ubiquitous water-soluble organic compounds with mass production worldwide, but their influence on coastal marine environments is still lack of consideration. In this study, we select a typical nearshore bay - the Jiaozhou Bay, which is surrounded by Qingdao - a city with modern manufacture, agriculture, aquaculture and service industry, as study area, to investigate the effect of LMWOAs on the nearshore marine environment, and their impact on seawater acidification in coastal areas. During Sep. 2016 to Aug. 2017, we identified three different LMWOAs - acetic acid (AA), formic acid (FA) and lactic acid (LA), with average concentrations of 46.7, 13.9 and 1.4 µmol·L-1 in the seawater of the bay, respectively. Due to the establishment of the Jiaozhou Bay Bridge, the seawater exchange capacity was weakened and thereby the concentration and stocks of AA and FA increased. As weak acids in seawater, the influence of LMWOAs on the seawater acidification of the Jiaozhou Bay was investigated. LMWOAs had significant impact on seawater pH and every 10 µmol·L-1 LMWOA caused an average of 0.02 pH unit decrease. From 2010 to 2017, pH value in the seawater of the bay decreased by about 0.103 and LMWOAs contributed about 83% of its decrease. Besides, two models were established to estimate the influence of LMWOAs on the seawater pH by applying the data set of dissolved inorganic carbon (DIC), total alkalinity (TA) and LMWOAs. The results showed that LMWOAs could enhance acidification of coastal seawater. Considering the importance of LMWOAs in seawater, it is necessary to evaluate their future changes in coastal marine environments. This study initiated a way to identify the source of LMWOAs in seawater and to evaluate their contribution to seawater acidification, and also provided a series of dataset for future study on LMWOAs in coastal environment.

Paracoccus amoyensis sp. nov., isolated from the surface seawater along the coast of Xiamen Island, China.

Strain 11-3T was isolated from the surface seawater along the coast of Xiamen Island, China. Cells were Gram-stain-negative, oxidase- and catalase-positive, short and rod-shaped, nonmotile, 0.5-1.0 µm in width and 1.0-2.0 µm in length. Growth of strain 11-3T was at temperature of 15-37°C (optimum 28-35°C), at pH of 5.0-11.0 (optimum 7.0-9.0) and at salinity range of 0-10 (optimum 0.5-1). Phylogenetic analysis based on the 16S rRNA gene sequence indicated that strain 11-3T belonged to the genus Paracoccus and had the highest similarity with Paracoccus caeni MJ17T (98.1 %), followed by Paracoccus xiamenensis 12-3T (97.1 %), Paracoccus zeaxanthinifaciens ATCC 21588T (97.1 %), Paracoccus aestuarii DSM 19484T (97.0 %), Paracoccus liaowanqingii 2251T (97.0 %), Paracoccus fistulariae KCTC 22803T (97.0 %) and other species of the genus Paracoccus (95.2-96.8 %). The DNA-DNA hybridization values between strain 11-3T and the selected strains (P. caeni MJ17T, P. xiamenensis 12-3T, P. zeaxanthinifaciens ATCC 21588T, P. aestuarii DSM 19484T and P. liaowanqingii 2251T) were 19.4, 19.5, 21.6, 19.3 and 19.8 %, respectively. Corresponding, their ANI values were 77.53, 75.61, 75.36, 75.73 and 75.33 %, respectively. The major fatty acid was summed feature 8 (C18:1 ω6c/ω7c). The major respiratory quinone was Q10. The polar lipids included phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), diphosphatidylglycerol (DPG), unidentified glycolipid (GL) and unidentified aminolipid (AL). The DNA G+C content of strain 11-3T was 60.1 %. Based on results of the phylogenetic analysis, phenotypic and chemotaxonomic characteristics, strain 11-3T represents a novel species of the genus Paracoccus, for which the name Paracoccus amoyensis sp. nov. is proposed. The type strain is 11-3T (=MCCC 1A16380T=KCTC 72689T).