Reversal of growth inhibition in Escherichia coli by bisulfite

Bisulfite inhibits growth, protein synthesis and RNA synthesis in micro-organisms. These inhibitory effects, in Escherichia coli K12, were diminished when certain amino acids were added to the minimal growth medium. The effects of individual amino acids were additive, synergistic and independent of their concentration. At 10 or 5 mM bisulfite, the presence of tyrosine had the greatest importance, while phenylalanine, glycine and methionine played a lesser role. E. coli cultures resume growth subsequent to bisulfite inhibition, after a lag whose duration is proportional to the initial concentration of added bisulfite. This resumption of growth was shown not to result from the depletion of bisulfite (by air oxidation or metabolism), but rather to adaptation to the presence of bisulfite concentrations that previously were inhibitory. The inhibitory effects of bisulfite were duplicated by lesser concentrations of cysteine. Both substances inhibited RNA synthesis by a mechanism that was independent of the stringent control system. A sulfite reductase deficient mutant was more resistant to inhibition by both bisulfite and cysteine. The various results indicate that growth inhibition by bisulfite is not due to covalent reactions with cellular target molecules, but to conversion of bisulfite to other substances, probably including cysteine, which in turn inhibit bacterial growth.