Muriiphilus fusiformis gen. nov., sp. nov., a novel non-marine bacterium belonging to the Roseobacter group, and reclassification of Maritimibacter lacisalsi (Zhong et al. 2015) as Muriicola lacisalsi gen. nov., comb. nov

An aerobic, Gram-stain-negative, non-sporulating, flagellated and spindle-like bacterium, designated HY14^T, was isolated from a pickle-processing factory wastewater sample. The isolate chemoheterotrophically grew at 4-42 °C (optimum, 35 °C) and pH 5.5-9.0 (optimum, pH 6.0-6.5). Salt was required for growth (0.5-12 % NaCl, w/v). A deep brown and water-soluble uncharacterized pigment was produced when grown in certain media. The predominant fatty acids (>5 %) included C_16 : 0, C_18 : 1  ω7c, 11-methyl C_18 : 1  ω7c and C_19 : 0 cyclo ω8c. The polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, two unidentified aminolipids, two unidentified phospholipids, two unidentified glycolipids and five unknown lipids. The major isoprenoid quinone was ubiquinone-10. Pairwise alignment based on 16S rRNA gene sequences indicated that strain HY14^T had the highest sequence similarity to genera Maritimibacter (95.61-96.05 %) and Boseongicola (95.82 %). Phylogenetic analysis based on core genome illustrated that strain HY14^T formed a monophyletic lineage with members of the genus Maritimibacter in the clade of the Roseobacter group in the family Rhodobacteraeceae. The core-gene average amino acid identity used to define bacterial genera by a threshold of 60-80 % was calculated to be 68.56-76.5 % between HY14^T and closely related taxa. Several genomic characteristics, such as carrying two RuBisCO-mediated pathways and different osmoprotectant transport pathways, exhibited the genotypic discrepancies of strain HY14^T. Based on the polyphasic taxonomic characterization, strain HY14^T is considered to represent a novel species of a novel genus belonging to the family Rhodobacteraeceae, for which the name Muriiphilus fusiformis gen. nov., sp. nov. is proposed. The type strain is HY14^T (=CGMCC 1.15973^T=KCTC 52499^T). Maritimibacter lacisalsi (Zhong et al. 2015) is considered to diverge from Maritimibacter alkaliphilus at the genus level, and should be reassigned as a novel genus, for which the name Muriicola lacisalsi gen. nov., comb. nov. is proposed.

Characteristics and Evolutionary Analysis of Photosynthetic Gene Clusters on Extrachromosomal Replicons: from Streamlined Plasmids to Chromids

Aerobic anoxygenic photoheterotrophic bacteria (AAPB) represent a bacteriochlorophyll a-containing functional group. Substantial evidence indicates that highly conserved photosynthetic gene clusters (PGCs) of AAPB can be transferred between species, genera, and even phyla. Furthermore, analysis of recently discovered PGCs carried by extrachromosomal replicons (exPGCs) suggests that extrachromosomal replicons (ECRs) play an important role in the transfer of PGCs. In this study, 13 Roseobacter clade genomes from seven genera that harbored exPGCs were used to analyze the characteristics and evolution of PGCs. The identification of plasmid-like and chromid-like ECRs among PGC-containing ECRs revealed two different functions: the spread of PGCs among strains and the maintenance of PGCs within genomes. Phylogenetic analyses indicated two independent origins of exPGCs, corresponding to PufC-containing and PufX-containing puf operons. Furthermore, the two different types of operons were observed within different strains of the same Tateyamaria and Jannaschia genera. The PufC-containing and PufX-containing operons were also differentially carried by chromosomes and ECRs in the strains, respectively, which provided clear evidence for ECR-mediated PGC transfer. Multiple recombination events of exPGCs were also observed, wherein the majority of exPGCs were inserted by replication modules at the same genomic positions. However, the exPGCs of the Jannaschia strains comprised superoperons without evidence of insertion and therefore likely represent an initial evolutionary stage where the PGC was translocated from chromosomes to ECRs without further combinations. Finally, a scenario of PGC gain and loss is proposed that specifically focuses on ECR-mediated exPGC transfer to explain the evolution and patchy distribution of AAPB within the Roseobacter clade.IMPORTANCE The evolution of photosynthesis was a significant event during the diversification of biological life. Aerobic anoxygenic photoheterotrophic bacteria (AAPB) share physiological characteristics with chemoheterotrophs and represent an important group associated with bacteriochlorophyll-dependent phototrophy in the environment. Here, characterization and evolutionary analyses were conducted for 13 bacterial strains that contained photosynthetic gene clusters (PGCs) carried by extrachromosomal replicons (ECRs) to shed light on the evolution of chlorophototrophy in bacteria. This report advances our understanding of the importance of ECRs in the transfer of PGCs within marine photoheterotrophic bacteria.

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)).