Occurence and regulation of Calvin cycle enzymes in non-autotrophic Beggiatoa strains

To date only marine strains of the genus Beggiatoa have been proven to have the capacity for lithoautotrophic growth. The two best characterized freshwater strains (B18LD and OH-75-2a) - previously tested with no evidence of autotrophic potential - were reinvestigated in the current study. Heterotrophically grown cells from exponential or early stationary phase showed extremely low ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) activities (0.002-0.2 nmol CO·mg prot min). After acetate limitation terminated growth both strains demonstrated increased RuBisCO activity with a maximum achieved 1-3 days into stationary phase. For a single growth cycle, activity could increase by more than 100-fold (strain OH-75-2a), but the highest activity achieved was less than 5% of that observed in a lithoautotrophic control. Phosphoribulokinase activity was approximately an order of magnitude greater than the corresponding RuBisCO activity and showed a similar pattern of regulation. A gene probe derived from the RuBisCO large subunit gene of Anacystis nidulans hybridized strongly with DNA from strain OH-75-2a and the autotrophic marine control but not with DNA from strain B18LD. © 1989 Springer-Verlag.