Desulfovibrio inopinatus, sp. nov., a new sulfate-reducing bacterium that degrades hydroxyhydroquinone (1,2,4-trihydroxy
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© Springer-Verlag 1997
O R I G I N A L PA P E R
Wolfram Reichenbecher · Bernhard Schink
Desulfovibrio inopinatus, sp. nov., a new sulfate-reducing bacterium that degrades hydroxyhydroquinone (1,2,4-trihydroxybenzene)
Received: 2 April 1997 / Accepted: 13 June 1997
Abstract A new sulfate-reducing bacterium was isolated from marine sediment with hydroxyhydroquinone (1,2,4trihydroxybenzene) 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. Key words Anaerobic degradation · Trihydroxybenzenes · Hydroxyhydroquinone · Pelobacter massiliensis · Desulfovibrio sp.
In some microorganisms, oxygenases have been found that form maleylacetate from hydroxyhydroquinone, which is further reduced to 3-oxoadipate. The pathway is known as the hydroxyhydroquinone variation to the pathway that usually involves catechol as the intermediate (Middelhoven 1993). Anaerobically fermenting bacteria such as Eubacterium oxidoreducens, Pelobacter acidigallici, Pelobacter massiliensis, and the homoacetogenic Holophaga foetida degrade trihydroxybenzenes through the phloroglucinol pathway (Schink and Pfennig 1982; Krumholz et al. 1987; Brune and Schink 1990; Schnell et al. 1991; Kreft and Schink 1993). One or three transhydroxylation reactions transform pyrogallol (1,2,3-trihydroxybenzene) or hydroxyhydroquinone to phloroglucinol (1,3,5-trihydroxybenzene) (Brune and Schink 1990; Brune et al. 1992), which is subsequently reduced to dihydrophloroglucinol by an NADPH-dependent reductase (Samain et al.1986; Brune and Schink 1992) and is further oxidized to three acetate residues. Sulfate-reducing bacteria degrade a large number of organic substrates including hydroxyben-zenes, hydroxybenzoates, aminobenzoates, trimethoxybenzoates, and several aldehydes (Hansen 1993). In the present paper, we report on the isolation and description of a new sulfate-reducing bacterium that degrades hydroxyhydroquinone as the sole aromatic substrate.
Introduction Hydroxyhydroquinone (1,2,4-trihydroxybenzene) is an intermediary product in the aerobic degradation of hydroxylated aro
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