Biosynthesis of glutamate in and benzoate in Syntrophus aciditrophicus

The anaerobic Deltaproteobacterium S. aciditrophicus SB grows non-syntrophically on crotonate, which is oxidized to acetate with formation of ATP and reduced via glutaconyl-CoA to cyclohexane-carboxylate and benzoate. Therefore, we assumed that glutaconyl-CoA decarboxylase must play an important role in this pathway catalyzing the carboxylation of crotonyl-CoA, which never has been observed in vivo before. Glutamate is usually synthesized from acetyl-CoA via citrate. However, no gene for Si-citrate synthase has been detected in the genome of S. aciditrophicus. Here, exploring an alternative way of glutamate biosynthesis via stereospecific Re-citrate synthase and the energy conserving glutaconyl-CoA decarboxylase will be presented.