Antibacterial function of inorganic polyphosphate on stress induced E. coli

Abstract

This study was performed to observe the antibacterial effect of inorganic polyphosphate on wild type E. coli and ppk/x(¥Ä) mutant in variable starvation. MIC of polyP for the bacterium was determined to be 1§·/§¢. PolyP added to the growing culture of wild type E. coli MG1655 at its exponential phase was as effective in inhibiting the growth of wild type E. coli MG1655 as polyP added at the very beginning of culture, however ppk/x(¥Ä) mutant CF5802 was not. More than 99% of the cell lost their viability determined by viable cell count when polyP was added to the culture of growing wild type E. coli MG1655 at concentration of 1§·/§¢, suggesting that polyP has a bactericidal effect. Antibacterial effect of polyP was shown significant effect in MOPS carbon starvation media Intracellular uncleotide release from the cell was increased by approx. 20% in the presence of polyP but was not reserved by the addition of divalent cations like Ca++ and Mg++. After polyP treatment, the transcriptional activity of possible polyP related genes observed on cell growth. Interestingly, spoT, relA, lon, ftsZ, were shown significant differences of transcriptional activity. In protein level, about 56kD, 58kD and 70kD proteins indicated different manner of expression depending on polyP treatment on variable starvation media. Wild type E. coli MG1655 shows visible filaments with increasing concentration of polyP but ppk/x(¥Ä) mutant CF5802 is not. The overall results suggest that polyP have a strong bactericidal activity against wild type E. coli.