Muricauda onchidii sp. nov., isolated from a marine invertebrate from South China Sea, and transfers of Flagellimonas algicola, Flagellimonas pacifica and Flagellimonas maritima to Muricauda algicola comb. nov., Muricauda parva nom. nov. and Muricauda aurantiaca nom. nov., respectively, and emended description of the genus Muricauda.

An aerobic, Gram-stain-negative, rod-shaped and non-motile strain (XY-359T) was isolated from the mouth of a marine invertebrate Onchidium species from the South China Sea. It grew at pH 6.0-8.5 (optimum, pH 7.5), at 15-37 °C (optimum, 30 °C) and in the presence of 0.5-4.5 % (w/v) NaCl (optimum, 2.5 %). It could not hydrolyse Tweens 20, 40, 60 or 80 and no flexirubin-type pigments were produced. The major polar lipids were phosphatidylethanolamine, one unidentified aminolipid, six unidentified phospholipids and two unidentified polar lipids. The major fatty acids were iso-C17:0 3-OH, iso-C15:1 G and iso-C15:0 3-OH. The respiratory quinone was MK-6. Strain XY-359T showed the greatest degree of 16S rRNA sequence similarity to Flagellimonas algicola AsT0115T (96.54 %), followed by Muricauda flava DSM 22638T (96.27 %). Phylogenetic analysis based on 16S rRNA gene sequences and 31 core genes indicated that strain XY-359T belongs to the genus Muricauda. The genome size of strain XY-359T was 4 207 872 bp, with 39.1 mol% of DNA G+C content. The average nucleotide identity and digital DNA-DNA hybridization values between strain XY-359T and F. algicola AsT0115T were 74.58 % and 18.5 %, respectively, and those between strain XY-359T and M. flava DSM 22638T were 74.2 % and 18.3 %. The combined phenotypic, chemotaxonomic and phylogenetic data suggest that strain XY-359T represents a novel species of the genus Muricauda, for which the name Muricauda onchidii sp. nov. is proposed. The type strain is XY-359T (=MCCC 1K03658T =KCTC 72218T). Moreover, based on the proposal of nesting Spongiibacterium and Flagellimonas within Muricauda by García (Validation List No. 193) and the analyses of phylogenetic trees and average amino acid identities in this study, the transfers of F. algicola, F. pacifica and F. maritima to the genus Muricauda as Muricauda algicola comb. nov., Muricauda parva nom. nov. and M. aurantiaca nom. nov., respectively, are proposed, with an emended description of the genus Muricauda.