Effect of Biogenic Polyamines on Rifampicin Accumulation in Escherichia coli Cells

The biogenic polyamines are well known to regulate cell wall permeability for antibiotics permeating the cell via porins. The effect of polyamines on the antibiotics transported by the non-porin route, such as rifampicin, has not been studied. In this work, the effect of intracellular putrescine, spermidine, and cadaverine on the efficiency of rifampicin accumulation, the bacterial susceptibility to rifampicin, the hydrophobicity of the cell surface, as well as the effect of polyamines on the expression of the marRAB operon was tested. None of the three polyamines studied affected the rate of rifampicin transport into the cell at the early stages (2 min). Under the longer exposure (60 min) a protective effect of cadaverine was observed, since the accumulation of rifampicin in cadaverine-free cells was higher compared to cadaverine-proficient ones. The absence of cadaverine in Escherichia coli cells increased their hydrophobicity. There was a direct relationship between the degree of hydrophobicity of the cell surface and the efficiency of rifampicin accumulation. Polyamines themselves did not affect the expression of marRAB operon, but modulated its expression induced by salicylate. Putrescine had no effect, spermidine decreased and cadaverine increased the expression level. Overall, polyamine biosynthesis plays a role in bacterial adaptation to rifampicin, as the strains unable to synthesize cadaverine or putrescine and spermidine were more sensitive than the wildtype strains. Cadaverine plays a special role in protecting against the effects of rifampicin; its intracellular concentration affected bacterial susceptibility to rifampicin.