A talk during dinner can be life-saving for bacteria

Among the Enterobacteriaceae, Serratia species are members of the subgroup that initially uses mixed acids as end products of fermentation processes but in time avoid lethal acidification of their environment by channeling a large amount of pyruvate from glycolysis into the butanediol pathway. We set out to investigate how this switch is regulated. Experiments indicate that in Serratia plymuthica RVH1 quorum sensing regulates the switch from mixed acids to butanediol fermentation. In a next step a screen for random transposon mutants that display both acidification and absence of acetoin production enabled us to isolate a RVH1 butanediol mutant in which a budB homologue, coding for alpha-acetolactate synthase, was inactivated. Subsequent cloning strategies led to the sequence of the complete budRAB operon, in which BudR is the regulator that responds to low pH conditions.