RESUMO
L-Ribulose 5-phosphate (L-Ru5P) was identified as the primary effector molecule of L-arabinose-induced bulge formation in Escherichia coli IFO 3545 observed in nutrient broth with 5% (w/v) sodium chloride. Hyperinduction of L-arabinose isomerase was due to exogenous sodium chloride and the resulting alteration in the balance of the L-arabinose-metabolizing enzymes resulted in accumulation of L-Ru5P. L-Ru5P induced the lysis of an L-arabinose-negative, L-Ru5P 4-epimerase-less mutant, ara-207, even when directly added to the medium but was not active against the wild-type strain. Some L-arabinose-utilizing (L-arabinose-resistant) revertants of ara-207 were still sensitive to L-Ru5P, indicating the involvement of another mutation in L-Ru5P-sensitivity other than genetic lack of L-Ru5P 4-epimerase. Among the various pentose phosphate esters tested, only L-Ru5P could induce lysis of ara-207. The lytic activity of L-Ru5P was attributed to its effect on bacterial sugar nucleotide metabolism which caused secondary accumulation of uridine 5'-diphosphate galactose (UDPGal), which provoked lysis induction.
