Cells are rods approximately 3–5 µm long and 0.8–1.0 µm wide and most cells clumped together. The optimum NaCl concentration required for growth is 0.045 % (w/v). Negative for catalase, oxidase, aesculin, indole production, nitrate reduction, urease reaction and gelatin hydrolysis. There is a positive reaction for arginine dihydrolase and glutamic acid decarboxylase but not for α-galactosidase, 6-phospho-β-galactosidase, β-galactosidase, arginine arylamidase, histidine arylamidase, α-glucosidase, β-glucosidase, α-arabinosidase, β-glucuronidase, N-acetyl-β-glucosaminidase, α-fucosidase, alkaline phosphatase, proline, leucyl glycine, phenylalanine, leucine, pyroglutamic acid, tyrosine, alanine, glycine, glutamyl glutamic acid or serine. The cells grew well on Medium 27. Growth occurs at 20–28 °C (optimum, 28 °C) and at pH 7.6–8.5 (optimum, pH 8.5). The major fermentation products produced during growth in Medium 27 are acetate and propionate. Cells grow only under reducing conditions in the absence of oxygen. The major cellular fatty acids present (at >10 % of the total) are C12 : 0, C14 : 0, C15 : 0 and C16:0. The type strain is BP5GT (=ICMP 24687T=JCM 35769T), isolated at the School of Biological Sciences, University of Auckland, New Zealand. It was isolated from the hindgut contents of the herbivorous marine fish Kyphosus sydneyanus (family Kyphosidae). The GenBank/EMBL/DDBJ accession number for the near full length 16S rRNA gene sequence of strain BP5GT is OP501869. The NCBI accession number for the genome sequence of strain BP5GT is CP092441.