A new sulfate-reducing bacterium was isolated from marine sediment with hydroxyhydroquinone (1,2,4- trihydroxybenzene) as the sole electron and carbon source. Strain HHQ 20 grew slowly with doubling times of > 20 h and oxidized hydroxyhydroquinone, lactate, pyruvate, ethanol, fructose, and ribose incompletely to acetate and carbon dioxide, with concomitant reduction of sulfate to sulfide. Cells were large, vibrio-shaped, and gram-negative with a G+C content of 49.7 mol%, and contained desulfoviridin. Based on analysis of the 16S rRNA sequence, strain HHQ 20 was found to be related to the genus Desulfovibrio but formed a separate line, thus justifying the establishment of a new species within this genus. Hydroxyhydroquinone was the only aromatic compound utilized among numerous hydroxybenzoates, hydroxybenzenes, methoxybenzoates, and methoxybenzenes tested, suggesting that phloroglucinol and resorcinol are not degradation intermediates. Cell-free extracts of strain HHQ 20 did not contain pyrogallol-phloroglucinol transhydroxylase activity. First experiments indicated that this strain uses a new reductive pathway for anaerobic hydroxyhydroquinone degradation
