Sphaerochaetaceae

Abstract Sphae.ro.chae.ta.ce'ae. N.L. fem. n. Sphaerochaeta type genus of the family; L. suff. – aceae , ending to denote a family; N.L. fem. pl. n. Sphaerochaetaceae the family of the genus Sphaerochaeta . Spirochaetes / Spirochaetia / Spirochaetales / Sphaerochaetaceae The family Sphaerochaetaceae accommodates the genera Sphaerochaeta, Parasphaerochaeta, and Pleomorphochaeta . Pleomorphic, anaerobic spirochetes with fermentative metabolisms. Gram‐negative spherical or pleomorphic cells occur singly, in pairs, or assembled in aggregates. Motile cells with spiral (helical) morphology are rare but may occur in the growth cycle in some species. Mesophilic or psychrophilic. Freshwater and marine; some species are halotolerant. Neutrophilic. Chemoorganoheterotrophic anaerobes. Fermentative growth is observed with carbohydrates including pentose and hexose monosaccharides, disaccharides, and soluble starch. Carbohydrate fermentation yields various products including acetate. No growth with cellulose or via H 2 /CO 2 reductive acetogenesis. May require yeast extract for growth. Oxidase‐negative. Isoprenoid quinones absent. Genome sizes range from 2.2 to 3.6 Mb. Free‐living, in microbial assemblages, or host associated. DNA G + C content (mol%) : 28.7–51 (genome sequence). Type genus : Sphaerochaeta Ritalahti et al. 2012 VP emend. Abt et al. 2012, Miyazaki et al. 2014, Arroua et al. 2017, Bidzhieva et al. 2020.