The strictly anaerobic gram-negative bacterium strain Fru22T grows at 50 degrees C in media containing up to 75 g NaCl l(-1). Hexoses and pentoses are fermented to equal molar amounts of acetate, propionate and succinate, and no CO2 is formed. An orange-red pigment similar to flexirrubin is produced during stationary phase upon exposure to light for several days. Cells also produce a surface-active extracellular compound which lowers the surface tension of the medium. This tenside is heat-tolerant up to 70 degrees C and is destroyed by treatment with proteinase K or trypsin, but not by lipase. Comparative 16S rDNA sequence analysis confirmed a phylogenetic affiliation of strain Fru22T to the phylum Bacteroides (Cytophaga/Flavobacterium/Bacteroides), moderately related to the genus Marinilabilia. Therefore, on the basis of phylogenetic, phenotypic and physiological evidence, a new genus, Anaerophaga, is proposed to harbour strain Fru22T (DSM 12881T, OCM 798T) which is described as the type strain of a new species, Anaerophaga thermohalophila gen. nov., sp. nov.