Maribacter algicola sp. nov., isolated from a marine red alga, Porphyridium marinum, and transfer of Maripseudobacter aurantiacus Chen et al. 2017 to the genus Maribacter as Maribacter aurantiacus comb. nov.

A Gram-stain-negative, strictly aerobic and moderately halophilic bacterial strain, designated strain PoM-212T, was isolated from a marine alga, Porphyridium marinum, in the Republic of Korea. Cells were catalase- and oxidase-positive rods with gliding motility without flagellum. Growth was observed at 20-40 °C (optimum, 30 °C) and pH 5.0-8.5 (pH 5.0-5.5) and in the presence of 0.5-5 % (w/v) NaCl (2-3 %). Strain PoM-212T contained iso-C15 : 1, iso-C15 : 0, iso-C17 : 0 3-OH and summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c) as major fatty acids and menaquinone-6 as the sole isoprenoid quinone. Phosphatidylethanolamine, three unidentified aminolipids and two unidentified polar lipids were detected as major polar lipids. The G+C content of the genomic DNA was 41.0 mol%. Strain PoM-212T was most closely related to Maribacter lutimaris KJ4T, Maripseudobacter aurantiacus CDA4T and Maribacter flavus C3T with 97.2, 97.2 and 97.0 % 16S rRNA gene sequence similarities, respectively, and it formed a distinct phylogenetic lineage from them within the genus Maribacter. Maripseudobacter aurantiacus formed a close phylogenetic lineage with Maribacter flavus with 99.7 % 16S rRNA gene sequence similarity, but their digital DNA-DNA hybridization value was 67.4 %. On the basis of its phenotypic, chemotaxonomic and molecular properties, strain PoM-212T represents a novel species of the genus Maribacter, for which the name Maribacter algicola sp. nov. is proposed. The type strain is PoM-212T (=KACC 19789T=JCM 32941T). The transfer of Maripseudobacter aurantiacus to the genus Maribacter as Maribacter aurantiacus comb. nov. is also proposed (type strain CDA4T=KCTC 52409T=MCCC 1K03210T).

Rhodophyticola porphyridii gen. nov., sp. nov., isolated from a red alga, Porphyridium marinum.

A Gram-stain-negative, strictly aerobic and moderately halophilic bacterium, designated strain MA-7-27T, was isolated from a marine red alga, Porphyridium marinum, in the Republic of Korea. The cells of strain MA-7-27T were non-motile rods showing oxidase- and catalase-positive activities. Growth of strain MA-7-27T was observed at 15-45 °C (optimum, 30 °C), pH 5.0-9.0 (pH 7.0) and in the presence of 0.0-5.0 % (w/v) NaCl (2.0 %). Strain MA-7-27T contained C10 : 0, summed feature 1 (comprising iso-C15 : 1 h and/or C13 : 1 3-OH) and summed feature 8 (comprising C18 : 1 ω7c and/or C18 : 1 ω6c) as the major fatty acids. The only isoprenoid quinone detected was ubiquinone-10. The major polar lipids of strain MA-7-27T were phosphatidylglycerol, two unidentified phospholipids and two unidentified aminolipids. The G+C content of the genomic DNA was approximately 63.6 mol%. Strain MA-7-27T was most closely related to the type strains of Boseongicola aestuarii BS-W15T and Nioella nitratireducens SSW136T with 96.98 % and 96.12 % 16S rRNA gene sequence similarities, respectively, but phylogenetic analyses showed that strain MA-7-27T formed a clearly distinct phylogenic lineage from the closely related strains. The phenotypic, chemotaxonomic and molecular properties support that strain MA-7-27T represents a novel genus of the family Rhodobacteraceae, for which the name Rhodophyticola porphyridii gen. nov., sp. nov. is proposed. The type strain is MA-7-27T (=KACC 18805T=JCM 31537T).

Aquicoccus porphyridii gen. nov., sp. nov., isolated from a small marine red alga, Porphyridium marinum.

A Gram-stain-negative, non-motile and aerobic bacterial strain, designated L1 8-17T, was isolated from a marine alga, Porphyridium marinum, in South Korea. Cells of strain L1 8-17T were found to be oxidase- and catalase-positive cocci without flagella. Growth of strain L1 8-17T was observed at 20-40 °C (optimum, 37 °C), pH 6.0-10.0 (optimum, pH 7.0-8.0) and in the presence of 0-7 % (w/v) NaCl (optimum, 2-3 %). The isoprenoid quinone detected was only ubiquinone-10. Summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c) and C16 : 0 were detected as major cellular fatty acids. The major polar lipids of strain L1 8-17T consisted of phosphatidylcholine, phosphatidylglycerol, phosphatidylethanolamine, an unidentified aminolipid, an unidentified phospholipid and an unidentified lipid. The G+C content of the genomic DNA was 59.3 mol%. Strain L1 8-17T was most closely related to Marimonas arenosa CAU 1311T, Tropicibacter naphthalenivorans C02T and Donghicola eburneus SW-277T with 96.68, 96.68 and 96.60 % 16S rRNA gene sequence similarities, respectively, but the strain formed a phylogenetic lineage clearly distinct from them within the family Rhodobacteraceae. On the basis of phenotypic, chemotaxonomic and molecular properties, strain L1 8-17T represents a novel genus of the family Rhodobacteraceae, for which the name Aquicoccus porphyridii gen. nov., sp. nov. is proposed. The type strain of the type species is L1 8-17T (KACC 18806T=JCM 31543T).

Replication of bacterial plasmids in the nucleus of the red alga Porphyridium purpureum.

Rhodophytes (red algae) are a diverse group of algae with great ecological and economic importance. However, tools for post-genomic research on red algae are still largely lacking. Here, we report the development of an efficient genetic transformation system for the model rhodophyte Porphyridium purpureum. We show that transgenes can be expressed to unprecedented levels of up to 5% of the total soluble protein. Surprisingly, the transgenic DNA is maintained episomally, as extrachromosomal high-copy number plasmid. The bacterial replication origin confers replication in the algal nucleus, thus providing an intriguing example of a prokaryotic replication origin functioning in a eukaryotic system. The extended presence of bacterial episomal elements may provide an evolutionary explanation for the frequent natural occurrence of extrachromosomal plasmids in red algae, and may also have contributed to the high rate of horizontal gene transfer from bacteria to the nuclear genome of Porphyridium purpureum and other rhodophytes.