The Tricarboxylic Acid Cycle of Heterogeneous and Swarmer Cell Populations of Rhodomicrobium vannielii Rm5

Summary: Studies on the tricarboxylic acid cycle of Rhodomicrobium vannielii Rm5 demonstrated that, unlike other Rhodospirillaceae, this organism has a functionally incomplete cycle, broken at 2-oxoglutarate dehydrogenase, under photoheterotrophic conditions. This enzyme was, however, synthesized when Rm. vannielii was grown under microaerophilic chemoheterotrophic conditions. The citrate synthase exhibited responses to inhibitors characteristic of Gram-negative organisms but, unlike many microbes exhibiting an incomplete cycle, was not inhibited by 2-oxoglutarate. Both NAD- and NADP-linked isocitrate dehydrogenase activity was detectable but the functional roles of these enzymes are unclear. No significant differences in enzyme activities or inhibitor sensitivities of enzymes were detected between heterogeneous cultures and synchronous swarmer cell populations.