Palleronia sediminis sp. nov. and Flavivirga algicola sp. nov., two marine bacteria isolated from offshore areas near Weihai

Two bacterial strains, designated SS33^T and Y03^T, were isolated from marine sediment and marine red alga collected on the coast of Weihai, PR China. Based on the results of 16S rRNA gene sequence analysis, strain SS33^T was found to be closely related to Primorskyibacter marinus PX7^T, Pelagivirga dicentrarchi YLY04^T, Palleronia marisminoris DSM 26347^T and Maribius pontilimi GH1-23^T with 94.8, 94.6, 94.5 and 94.5 % sequence similarity; strain Y03^T was found to be closest to Flavivirga aquimarina EC2D5^T, Flavivirga eckloniae ECD14^T and Flavivirga amylovorans JC2681^T with 96.4, 96.1 and 96.0 % sequence similarity. Strain SS33^T grew at 4-37 °C (optimum, 33 °C), at pH 6.0-9.5 (optimum, pH 7.5-8.0) and in the presence of 0-10 % (w/v) NaCl (optimum, 3.0 %). Chemotaxonomic analysis of strain SS33^T showed that the predominant respiratory quinone was ubiquinone-10. The major fatty acids (>10.0 %) included C_18 : 1  ω7c and C_16 : 0. The major polar lipids included phosphatidylglycerol, phosphatidylcholine, one unidentified phospholipid, one unidentified glycolipid, one unidentified polar lipid and two unidentified aminolipids. Strain Y03^T grew at 15-40 °C (optimum, 28 °C), at pH 6.5-8.0 (optimum, pH 7.0) and in the presence of 0.5-9.0 % (w/v) NaCl (optimum, 2.0%). Chemotaxonomic analysis showed that the predominant respiratory quinone was menaquinone-6. The major fatty acids (>10.0 %) included iso-C_15 : 0, iso-C_15 : 1 G, iso-C_17 : 0 3-OH and iso-C_15 : 0 3-OH. The major polar lipids included phosphatidylethanolamine, one unidentified phospholipid, one unidentified aminolipid and four unidentified polar lipids. Based on the polyphasic data, strain SS33^T is considered to represent a novel species of the genus Palleronia, for which the name Palleronia sediminis sp. nov. is proposed, with the type strain SS33^T (=KCTC 62986^T=MCCC 1H00387^T). Strain Y03^T is considered to represent a novel species of the genus Flavivirga, for which the name Flavivirga algicola sp. nov. is proposed, with the type strain Y03^T (=KCTC 72001^T=MCCC 1H00386^T).

Roseobacters in a Sea of Poly- and Paraphyly: Whole Genome-Based Taxonomy of the Family Rhodobacteraceae and the Proposal for the Split of the "Roseobacter Clade" Into a Novel Family, Roseobacteraceae fam. nov

The family Rhodobacteraceae consists of alphaproteobacteria that are metabolically, phenotypically, and ecologically diverse. It includes the roseobacter clade, an informal designation, representing one of the most abundant groups of marine bacteria. The rapid pace of discovery of novel roseobacters in the last three decades meant that the best practice for taxonomic classification, a polyphasic approach utilizing phenotypic, genotypic, and phylogenetic characteristics, was not always followed. Early efforts for classification relied heavily on 16S rRNA gene sequence similarity and resulted in numerous taxonomic inconsistencies, with several poly- and paraphyletic genera within this family. Next-generation sequencing technologies have allowed whole-genome sequences to be obtained for most type strains, making a revision of their taxonomy possible. In this study, we performed whole-genome phylogenetic and genotypic analyses combined with a meta-analysis of phenotypic data to review taxonomic classifications of 331 type strains (under 119 genera) within the Rhodobacteraceae family. Representatives of the roseobacter clade not only have different environmental adaptions from other Rhodobacteraceae isolates but were also found to be distinct based on genomic, phylogenetic, and in silico-predicted phenotypic data. As such, we propose to move this group of bacteria into a new family, Roseobacteraceae fam. nov. In total, reclassifications resulted to 327 species and 128 genera, suggesting that misidentification is more problematic at the genus than species level. By resolving taxonomic inconsistencies of type strains within this family, we have established a set of coherent criteria based on whole-genome-based analyses that will help guide future taxonomic efforts and prevent the propagation of errors.

Analysis of 1,000+ Type-Strain Genomes Substantially Improves Taxonomic Classification of Alphaproteobacteria

The class Alphaproteobacteria is comprised of a diverse assemblage of Gram-negative bacteria that includes organisms of varying morphologies, physiologies and habitat preferences many of which are of clinical and ecological importance. Alphaproteobacteria classification has proved to be difficult, not least when taxonomic decisions rested heavily on a limited number of phenotypic features and interpretation of poorly resolved 16S rRNA gene trees. Despite progress in recent years regarding the classification of bacteria assigned to the class, there remains a need to further clarify taxonomic relationships. Here, draft genome sequences of a collection of genomes of more than 1000 Alphaproteobacteria and outgroup type strains were used to infer phylogenetic trees from genome-scale data using the principles drawn from phylogenetic systematics. The majority of taxa were found to be monophyletic but several orders, families and genera, including taxa recognized as problematic long ago but also quite recent taxa, as well as a few species were shown to be in need of revision. According proposals are made for the recognition of new orders, families and genera, as well as the transfer of a variety of species to other genera and of a variety of genera to other families. In addition, emended descriptions are given for many species mainly involving information on DNA G+C content and (approximate) genome size, both of which are confirmed as valuable taxonomic markers. Similarly, analysis of the gene content was shown to provide valuable taxonomic insights in the class. Significant incongruities between 16S rRNA gene and whole genome trees were not found in the class. The incongruities that became obvious when comparing the results of the present study with existing classifications appeared to be caused mainly by insufficiently resolved 16S rRNA gene trees or incomplete taxon sampling. Another probable cause of misclassifications in the past is the partially low overall fit of phenotypic characters to the sequence-based tree. Even though a significant degree of phylogenetic conservation was detected in all characters investigated, the overall fit to the tree varied considerably.

Primorskyibacter insulae sp. nov., isolated from the junction between the ocean and a freshwater spring

A Gram-stain-negative, aerobic, non-spore-forming, non-flagellated and rod-shaped bacterial strain, designated SSK3-2T, was isolated from the locality where the ocean and a freshwater spring meet at Jeju island, South Korea, and subjected to a polyphasic taxonomic study. Strain SSK3-2T grew optimally at 30 °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 revealed that strain SSK3-2T clustered with the type strain of Primorskyibacter sedentarius, with which it exhibited 97.3 % sequence similarity. Strain SSK3-2T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the major fatty acid. The major polar lipids detected in strain SSK3-2T were phosphatidylcholine, phosphatidylglycerol, one unidentified lipid and one unidentified aminolipid. The DNA G+C content of strain SSK3-2T was 60.6 mol% and its mean DNA–DNA relatedness value with P. sedentarius JCM 16874T was 19 %. Differential phenotypic properties, together with phylogenetic and genetic distinctiveness, revealed that strain SSK3-2T is separated from P. sedentarius. On the basis of the data presented, strain SSK3-2T is considered to represent a novel species of the genus Primorskyibacter, for which the name Primorskyibacter insulae sp. nov. is proposed. The type strain is SSK3-2T ( = KCTC 42602T = CECT 8871T).

Pseudopelagicola gijangensis gen. nov., sp. nov., isolated from the sea squirt Halocynthia roretzi

A Gram-stain-negative, aerobic, non-motile, rod-shaped bacterial strain, designated YSS-7T, was isolated from a sea squirt (Halocynthia roretzi) collected from the South Sea of South Korea. Strain YSS-7T grew optimally at 25 °C, at pH 7.0–8.0 and in the presence of 2.0 % (w/v) NaCl. Phylogenetic trees based on 16S rRNA gene sequences revealed that strain YSS-7T clustered with the type strains of Pelagicola litoralis , Planktotalea frisia , Pacificibacter maritimus and Roseovarius marinus . Strain YSS-7T exhibited the highest 16S rRNA gene sequence similarity (97.7 %) to the type strain of Pelagicola litoralis and sequence similarity of more than 96.0 % to the type strains of some other species. Strain YSS-7T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c and 11-methyl C18 : 1ω7c as the major fatty acids. The major polar lipids of strain YSS-7T were phosphatidylcholine, phosphatidylglycerol, an unidentified aminolipid and an unidentified lipid. The fatty acid and polar lipid profiles of strain YSS-7T were different from those of the type strains of phylogenetically related species. The DNA G+C content of strain YSS-7T was 55.5 mol%. Other phenotypic properties demonstrated that strain YSS-7T is distinguished from phylogenetically related species. On the basis of the data presented, strain YSS-7T is considered to represent a novel genus and species, for which the name Pseudopelagicola gijangensis gen. nov., sp. nov. is proposed. The type strain of Pseudopelagicola gijangensis is YSS-7T ( = KCTC 42049T = CECT 8540T).

Aestuariivita boseongensis gen. nov., sp. nov., isolated from a tidal flat sediment

A Gram-stain-negative, aerobic, non-motile and coccoid, ovoid or rod-shaped bacterial strain, BS-B2T, which was isolated from a tidal flat sediment at Boseong in South Korea, was characterized taxonomically. Strain BS-B2T grew optimally at 30 °C, at pH 7.0–8.0 and in the presence of 2.0 % (w/v) NaCl. The novel strain exhibited highest 16S rRNA gene sequence similarity (97.4 %) to Marivita geojedonensis DPG-138T. Neighbour-joining, maximum-likelihood and maximum-parsimony phylogenetic trees based on 16S rRNA gene sequences revealed that strain BS-B2T is closely related to Primorskyibacter sedentarius KMM 9018T, showing 96.5 % sequence similarity. Strain BS-B2T contained Q-10 as the predominant ubiquinone and C18 : 1ω7c as the predominant fatty acid. The polar lipid profile of strain BS-B2T comprised phosphatidylcholine, phosphatidylglycerol, one unidentified aminolipid and one unidentified lipid as major components, and differentiated it from the type strains of P. sedentarius and M. geojedonensis . The DNA G+C content of strain BS-B2T was 62.2 mol%. Differential phenotypic properties, together with the phylogenetic and chemotaxonomic data, demonstrated that strain BS-B2T can be distinguished from phylogenetically related genera as well as P. sedentarius and M. geojedonensis . On the basis of the data presented, strain BS-B2T is considered to represent a novel species of a new genus, for which the name Aestuariivita boseongensis gen. nov., sp. nov. is proposed. The type strain of Aestuariivita boseongensis is BS-B2T ( = KCTC 42052T = CECT 8532T).

Loktanella maritima sp. nov. isolated from shallow marine sediments

An aerobic, Gram-stain-negative, non-motile bacterium, KMM 9530T, was isolated from a sediment sample collected from the Sea of Japan seashore. Comparative 16S rRNA gene sequence analysis positioned novel strain KMM 9530T in the genus Loktanella as a separate line adjacent to Loktanella sediminilitoris KCTC 32383T, Loktanella tamlensis JCM 14020T and Loktanella maricola JCM 14564T with 98.5–98.2 % sequence similarity. Strain KMM 9530T was characterized by its weak hydrolytic capacity and inability to assimilate most organic substrates. The major isoprenoid quinone was Q-10, polar lipids consisted of phosphatidylcholine, phosphatidylglycerol, diphosphatidylglycerol, an unknown phospholipid, an unknown aminolipid and unknown lipids, and the major fatty acid was C18 : 1ω7c. On the basis of phylogenetic analysis, DNA–DNA hybridization and phenotypic characterization, it can be concluded that the novel strain KMM 9530T represents a novel species in the genus Loktanella , for which the name Loktanella maritima sp. nov. is proposed. The type strain of the species is KMM 9530T ( = NRIC 0919T = JCM 19807T).