The description of the phylum is drawn from the shared characteristics of the members of its constituent classes with validly published descriptions. Morphological properties are highly variable (vibrio, rods, cocci, filaments). Gram-stain-negative, no spore formation. Strictly anaerobic chemoorganotrophic, chemolithoheterotrophic or chemolithoautotrophic growth by respiratory or fermentative metabolism. Some members can grow by disproportionation or oxidation of reduced sulphur compounds. Some members can grow only in the presence of H2/formate-utilizing partners in syntrophic associations. When organic compounds are used, these are oxidized to acetate or completely to carbon dioxide. Members can be mesophilic, thermophilic or psychrophilic. Occurs in various aquatic environments. The phylum represents a distinct monophyletic lineage as supported by concatenated protein and 16S rRNA gene trees.
The type class of the phylum is Desulfobacteria.