Aestuarium zhoushanense is a later heterotypic synonym of Marivivens donghaensis, and transfer of Paradonghicola geojensis to the genus Marivivens as Marivivens geojensis comb. nov

The 16S rRNA genes of Aestuarium zhoushanense G7T and Paradonghicola geojensis FJ12T shared 100 % sequence identity with Marivivens donghaensis AM-4T. Phylogeny of 16S rRNA gene sequences showed that the three type strains formed a monophyletic clade within the genus Marivivens . Whole genome sequence comparisons showed that three type strains shared 46.7–69.7 % digital DNA–DNA hybridization, 92.1–96.4 % average nucleotide identity and 96.2–98.1 % average amino acid identity. The high 16S rRNA gene similarity values show that three type strains should belong to the same genus. The pan-genome of the five strains contained 5754 genes including 1877 core genes. Based on the principle of priority, we propose that A. zhoushanense Yu et al. 2019 is a later heterotypic synonym of M. donghaensis Park et al. 2016, and P. geojensis should be reclassified as Marivivens geojensis comb. nov., respectively.

Salibaculum halophilum gen. nov., sp. nov. and Salibaculum griseiflavum sp. nov., in the family Rhodobacteraceae

Two Gram-stain-negative, moderately halophilic, non-motile, rod-shaped, pale yellow, and aerobic strains, designated WDS1C4^T and WDS4C29^T, were isolated from a marine solar saltern in Weihai, Shandong Province, PR China. Growth of strain WDS1C4^T occurred at 10-45 °C (optimum, 37 °C), with 4-16 % (w/v) NaCl (optimum, 8 %) and at pH 6.5-9.0 (optimum, pH 7.5). Growth of strain WDS4C29^T occurred at 10-45 °C (optimum, 40 °C), with 2-18 % (w/v) NaCl (optimum, 6 %) and at pH 6.5-9.0 (optimum, pH 7.5). Q-10 was the sole respiratory quinone of the two strains. The major polar lipids of strains WDS1C4^T and WDS4C29^T were phosphatidylglycerol, phosphatidylethanolamine and phosphatidylcholine. The major cellular fatty acid in strains WDS1C4^T and WDS4C29^T was C_18 : 1  ω7c, and the genomic DNA G+C contents of strains WDS1C4^T and WDS4C29^T were 67.6 and 63.3 mol%, respectively. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strains WDS1C4^T and WDS4C29^T were members of the family Rhodobacteraceae and showed 94.3 and 95.3 % similarities to their closest relative, Celeribacter indicus, respectively. The similarity between WDS1C4^T and WDS4C29^T was 97.3 %. Differential phenotypic and genotypic characteristics of the two isolates from recognized genera showed that the two strains should be classified as representing two novel species in a new genus for which the names Salibaculum halophilum gen. nov., sp. nov. (type species, type strain WDS1C4^T=MCCC 1H00179^T=KCTC 52542^T) and Salibaculum griseiflavum sp. nov. (WDS4C29^T=MCCC 1H00175^T=KCTC 52541^T) are proposed.

Marivivens aquimaris sp. nov., isolated from seawater

A Gram-stain-negative, strictly aerobic, non-flagellated, rod-shaped bacterium, designated GSB7^T, was isolated from seawater collected at the Yellow Sea coast of South Korea. Catalase and oxidase activities were positive. Growth occurred at pH 6.0-9.0 (optimum pH 7.0), 10-40 °C (optimum 30 °C) and with 0-8% NaCl (optimum 1-2%). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain GSB7^T belonged to the genus Marivivens, showing the sequence similarities of 96.3, 96.1, and 96.0% with Marivivens niveibacter HSLHS2^T, Limimaricola hongkongensis DSM17492^T, and Marivivens donghaensis AM-4^T, respectively. The respiratory quinone was ubiquinone-10 and the major fatty acids were summed feature 8 (C_18:1 ω7c and/or C_18:1 ω6c), C_18:1 ω7c 11-methyl, C_16:0 and C_10:0 3-OH. The polar lipids comprised phosphatidylglycerol, diphosphatidylglycerol, one unidentified aminolipid, and five unidentified lipids. The DNA G + C content calculated from the whole-genome sequence was 60.6 mol%. On the basis of phenotypic, chemotaxonomic and genotypic characteristics presented in this study, strain GSB7^T is suggested to represent a novel species of the genus Marivivens, for which the name Marivivens aquimaris sp. nov. is proposed. The type strain is GSB7^T (= KCTC 82026^T = JCM 34042^T).

Bacterial-derived nutrient and carbon source-sink behaviors in a sandy beach subterranean estuary

Microbial communities in subterranean estuaries play important roles in the biogeochemical cycle. However, the microorganisms associated with biogeochemical behaviors in subterranean estuaries have received little attention. Here, the bacterial communities were compared between the fresh and saline groundwater in a subterranean estuary. Correlation analysis between bacterial groups and salinity indicated that different species represented different groundwater types. The key bacterial groups found along the subterranean estuaries have been shown to influence organic pollutant degradation and nitrate utilization. These species may be potential candidates for the in situ bioremediation of subterranean estuaries that are contaminated with pollutants. The utilization of nitrate and organic pollutants by bacteria in subterranean estuaries serves as a nitrate sink and inorganic carbon source. Our results show the role of bacteria in remediating pollutants through submarine groundwater discharge (SGD) to the coastal ocean, and specific species may be helpful in selecting reasonable groundwater end-members and reducing SGD uncertainties.

Polycyclic Aromatic Hydrocarbons Degradation by Aquatic Bacteria Isolated from Khazar Sea, the World’s Largest Lake

Background: Aquatic microorganisms have an important role in the bioremediation of environmental pollutants. Polycyclic Aromatic Hydrocarbons (PAHs) are described as dangerous pollutants that can bind covalently to the nucleic acids, causing mutations. Therefore, they have carcinogenic and toxic properties. Also, are involved in diseases such as asthma, lung dysfunction, and chronic bronchitis. This study aimed to isolate and characterize aquatic bio-degrading bacteria from the world’s largest lake, Khazar, with the ability to use PAHs as only carbon source. Methods: Samples were taken from the estuary of Siah Rud River (Mazandaran province, Iran) and Fereydunkenar beach leading to isolation of twenty-three bacteria on marine agar and sea water media. The isolates were cultured on separate ONR7a medium, each supplemented with only one PAH; as the sole carbon source; including naphthalene, phenanthrene, and anthracene. Results: Eleven bacterial isolates were able to grow on supplemented media: TBZ-E1, TBZ-E2, TBZ-E3, TBZ-S12, TBZ-S16, TBZ-E20, TBZ-SF2, TBZ-F1, TBZ-F2, TBZ-F3 and TBZ2. These isolates belong to Alteromonas, Marivivens, Pseudoalteromonas, Vibrio, Shewanella, Photobacterium, Mycobacterium and Pseudomonas genera. The qualitative analysis showed that the consortium of isolates TBZ-F1, TBZ-F2, TBZ-F3, TBZ-SF2, and TBZ2 displayed the highest degradation rate for phenanthrene and naphthalene. Naphthalene, phenanthrene, and anthracene were potently degraded by TBZ2 and TBZ-SF2 and accordingly were subjected to measure degradation potential of mentioned PAHs. Conclusion: The bacterial isolates of Caspian lake have a critical duty in biodegradation of PAHs. These isolates are representative samples of the bacterial population of this lake, participating in the purification process of this habitat.

Microbial community structure associated with submarine groundwater discharge in northern Java (Indonesia)

Submarine groundwater discharge (SGD) can be an important pathway for chemical or biological pollutants from land to the ocean around the world. However, studies on the microbial communities associated with SGD in Southeast Asia, which has been hypothesized as SGD hotspot, remain scarce. In this study, we examined the microbial community composition with 16S rRNA gene sequencing along the hydrological continuum of an SGD site in a tropical urban area of Indonesia. Of the observed parameters in this study, salinity and temperature were the most determinant variables explaining patterns in microbial community composition. The bacterial taxon Burkholderiaceae was predominantly found in low salinity samples, including those from terrestrial groundwater and brackish pore water, while cyanobacteria of the genus Synechococcus sp. CC9902 were indicative of saline SGD and seawater samples. The composition of microbial taxa in each sample pointed to the influence of shallow terrestrial groundwater in the beach pore water, while seawater recirculation dominated the SGD sampling points situated further offshore. We identified taxa containing fecal indicators and potential pathogens at the SGD compartments; however, while a likely explanation, we could not conclude with certainty that SGD was a conduit for these bacteria. Overall, the results from this study show that microbial community analysis can highlight hydrological processes and water quality at the SGD site; thus, they could be useful for environmental policymakers to formulate water management strategies in coastal areas.