Marinibacterium profundimaris gen. nov., sp. nov., isolated from deep seawater

Physiological and genomic features of Paraoceanicella profunda gen. nov., sp. nov., a novel piezophile isolated from deep seawater of the Mariana Trench

A novel piezophilic alphaproteobacterium, strain D4M1^T, was isolated from deep seawater of the Mariana Trench. 16S rRNA gene analysis showed that strain D4M1^T was most closely related to Oceanicella actignis PRQ‐67^T (94.2%), Oceanibium sediminis O448^T (94.2%), and Thioclava electrotropha ElOx9^T (94.1%). Phylogenetic analyses based on both 16S rRNA gene and genome sequences showed that strain D4M1^T formed an independent monophyletic branch paralleled with the genus Oceanicella in the family Rhodobacteraceae. Cells were Gram‐stain‐negative, aerobic short rods, and grew optimally at 37°C, pH 6.5, and 3.0% (w/v) NaCl. Strain D4M1^T was piezophilic with the optimum pressure of 10 MPa. The principal fatty acids were C_18:1ω7c/C_18:1ω6c and C_16:0, major respiratory quinone was ubiquinone‐10, and predominant polar lipids were phosphatidylglycerol, phosphatidylethanolamine, and an unidentified aminophospholipid. The complete genome contained 5,468,583‐bp with a G + C content of 70.2 mol% and contained 4,855 protein‐coding genes and 78 RNA genes. Genomic analysis revealed abundant clues on bacterial high‐pressure adaptation and piezophilic lifestyle. The combined evidence shows that strain D4M1^T represents a novel species of a novel genus in the family Rhodobacteraceae, for which the name Paraoceanicella profunda gen. nov., sp. nov. is proposed (type strain D4M1^T = MCCC 1K03820^T = KCTC 72285^T).

Comparative Genomics and Mutational Analysis Reveals a Novel XoxF-Utilizing Methylotroph in the Roseobacter Group Isolated From the Marine Environment

The Roseobacter group comprises a significant group of marine bacteria which are involved in global carbon and sulfur cycles. Some members are methylotrophs, using one-carbon compounds as a carbon and energy source. It has recently been shown that methylotrophs generally require a rare earth element when using the methanol dehydrogenase enzyme XoxF for growth on methanol. Addition of lanthanum to methanol enrichments of coastal seawater facilitated the isolation of a novel methylotroph in the Roseobacter group: Marinibacterium anthonyi strain La 6. Mutation of xoxF5 revealed the essential nature of this gene during growth on methanol and ethanol. Physiological characterization demonstrated the metabolic versatility of this strain. Genome sequencing revealed that strain La 6 has the largest genome of all Roseobacter group members sequenced to date, at 7.18 Mbp. Multilocus sequence analysis (MLSA) showed that whilst it displays the highest core gene sequence similarity with subgroup 1 of the Roseobacter group, it shares very little of its pangenome, suggesting unique genetic adaptations. This research revealed that the addition of lanthanides to isolation procedures was key to cultivating novel XoxF-utilizing methylotrophs from the marine environment, whilst genome sequencing and MLSA provided insights into their potential genetic adaptations and relationship to the wider community.

Nitropelagius marinus gen. nov., sp. nov., Isolated From Seawater, Je-bu island, South Korea [corrected]

A Gram-stain-negative, non-spore forming, non-motile and aerobic strain, designated JB22(T), was isolated from seawater, Je-bu Island, South Korea. Strain JB22(T) was catalase and oxidase positive. Optimal growth of JB22(T) was observed at 30 °C and pH 7.0. NaCl tolerance range was 1-9 % (w/v) with an optimum of 2.0 % concentration. The phylogenetic analysis based on 16S rRNA gene sequence of strain JB22(T) showed the highest sequence similarity to those of Pelagicola litorisediminis D1-W8(T) (95.8 %), Roseovarius litoreus GSW-M15(T) (95.2 %), Roseovarius aestuarii SMK-122(T) (95.0 %), Donghicola eburmeus SW-277(T) (95.0 %), and Roseovarius halotolerans HJ50(T) (94.9 %). It contained ubiquine-10 as the major respiratory quinone and C18:1 ω7c (69.3 %), :0 (9.9 %), C18:1 ω7c 11-methyl (9.6 %) as the major fatty acid. The polar lipid profile included phosphatidylcholine, phosphatidylglycerol, and unidentified aminolipid. The DNA G+C content of the strain JB22(T) was 47 mol  %. Based on physiological and chemotaxonomic characteristics, strain JB22(T) should be regarded as a new genus of the family Rhodobacteraceae, for which the Nitropelagi marinus gen. nov., sp. nov. is proposed. The type strain is JB22(T) (= KEMB 3001-101(T) = JCM 30822(T)).