Identification and classification of Croceivirga thetidis sp. nov., a marine Flavobacteriaceae isolated from the hard coral Acropora

An update on novel taxa and revised taxonomic status of bacteria isolated from aquatic host species described in 2022-2023

The description of new taxa and nomenclature updates to currently known taxa from aquatic animal species continues. After a review of the literature from 2022 and 2023, multiple lists of bacteria, including members of Phylum Planctomycetota, were compiled. As with the previous review, most bacteria are oxidase-positive Gram-negative bacilli with familiar families including new taxa in Aeromonadaceae, Flavobacteriaceae, and Vibrionaceae. A number of Gram-positive bacilli are described including new taxa in the Nocardioides, Paenibacillus, and Streptomyces genera. Two anaerobic species are listed, and one new member of Family Planctomycetaceae is noted. Revised taxa are briefly mentioned. The majority of new and revised taxa are isolated from healthy aquatic animals, and therefore, the role of these new bacteria in health and disease is unknown. Bacteria with pathogenic association and potential production of bioactive substances are highlighted.

Flagellimonas algarum sp. nov., isolated from dense mats of filamentous algae

A novel Gram-stain-negative, strictly aerobic, rod-shaped, light-yellow-pigmented, and chemo-organoheterotrophic bacterium, designated DF-77T, was isolated from dense mats of filamentous algae collected in March 2004 at Okinawa in Japan. The microorganism grew at 0-2.0% NaCl concentrations (w/v), pH 6.0-9.0, and 20-30 °C. The 16S rRNA gene sequence-based phylogenetic tree demonstrated that the strain DF-77T is a novel member of the family Flavobacteriaceae and was greatly related to Flagellimonas nanhaiensis SM1704T with sequence similarity of 95.5%. The main fatty acids were iso-C15:1 G, iso-C15:0, and iso-C17:0 3-OH, and the only isoprenoid quinone was menaquinone-6. The dominant polar lipids were phosphatidylethanolamine, two unidentified aminolipids, an unidentified phosphoaminolipid, and four unidentified lipids. The genome size of strain DF-77T was 3.60 Mbp with a DNA G + C content of 47.5%. The average nucleotide identity (ANI) value between the genomes of strain DF-77T and its closely related species was 69.8-70.7%. The digital DNA - DNA hybridization (dDDH) value of strain DF-77T with the strain of F. nanhaiensis SM1704T was 16.8%. The genome of the strain DF-77T revealed that it encoded several genes involved in bio-macromolecule degradation, indicating a high potential for producing industrially useful enzymes. Consequently, the strain is described as a new species in the genus Flagellimonas, for which the name Flagellimonas algarum sp. nov., is proposed with the type strain DF-77T (= KCTC 72791T = NBRC 114251T).

Erythrobacter rubeus sp. nov., a carotenoid-producing alphaproteobacterium isolated from coastal seawater

A study based on a polyphasic taxonomic approach was carried out to identify and classify a novel marine alphaproteobacterium, designated as KMU-140^T, isolated from coastal seawater collected at Jeju Island, Republic of Korea. Cells of strain KMU-140^T were spherical, Gram-stain-negative, reddish-orange colored, strictly aerobic, catalase- and oxidase-positive, non-motile, and chemoorganoheterotrophic. The novel isolate was able to grow at NaCl concentrations of 0-5%, pH 6.0-9.5, and 10-45 °C. A phylogenetic analysis based on the 16S rRNA gene sequence showed that strain KMU-140^T belongs to the family Erythrobacteraceae and was most closely related to Erythrobacter longus OCh101^T (98.7%). Strain KMU-140^T contained ubiquinone-10 (Q-10) as the only respiratory quinone and C18:1 ω7c, iso-C18:0, and C16:0 as the main (> 10%) cellular fatty acids. Strain KMU-140^T produced carotenoid compounds that rendered the cell biomass a reddish-orange color. The assembled draft genome size of strain KMU-140^T was 3.04 Mbp with G + C content of 60.6 mol%. The average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), and average amino acid identity (AAI) values of KMU-140^T and the species of the genus Erythrobacter were found to be 76.6-78.4%, 14.0-18.7%, and 69.6-77.8%, respectively. Phosphatidylethanolamine, phosphatidylglycerol, an unidentified phospholipid, and two unidentified lipids were identified as major polar lipids. On the basis of the polyphasic taxonomic features presented, the strain is considered to represent a novel species of the genus Erythrobacter for which the name Erythrobacter rubeus sp. nov. is proposed. The type strain of E. rubeus sp. nov. is KMU-140^T (= KCCM 90479^T = NBRC 115159^T).