NOVEL ASPECTS OF BENZOATE AND CROTONATE METABOLISM

In anoxic environments, many aromatic compounds (AC)§are transformed to benzoylCoA, prior to§dearomatization and ring cleavage. Due to the§resonance stability of the aromatic ring, AC are§difficult to degrade in the absence of O2. Benzoate§degradation in methanogenic ecosystems is mediated by§syntrophic association of a fermentative bacterium§with a H2/formate-using methanogen. The metabolism of§crotonate in the strictly anaerobic bacteria§S.aciditrophicus (SB) was studied and§indicated that cyclohexane carboxylate and acetate as§end products. In addition to benzoate fermentation,§SB as the ability to use benzoate as an electron§acceptor with crotonate as the electron§donor.Phototrophic and denitrifying bacteria couple§the hydrolysis of 2 ATP to reduce benzoylCoA to§cyclohexediene carboxylCoA. The use of§such an energy intensive reaction by fermentative§bacteria such as SB has been questioned since it is§not clear how net ATP synthesis would occur. The§utilization of fluorobenzoate by SB allowed the§detection of a fluorinated diene intermediate.§Proteomic analysis of SB grown with crotonate or§benzoate allowed the identification of gene§products involved in benzoate metabolism.