Abstract

This study has two purposes: (1) to see whether the pnp and pap genes, encoding polynucleotide phosphorylase and poly(A) polymerase, respectively, are essential for the growth of the Escherichia coli (E. coli) strains under laboratory conditions; (2) to see whether oxidative stress by the addition of Tert-Butyl Hydroperoxide (TBHP) to the cultures would differentially affect growth of wild-type (WT) and pnp,pap mutant. The optical density of the cultures were measured at wavelengths of 600nm. Increased RNA oxidation is related with cell death. Therefore, growth experiments under oxidative stress can be used to identify if the genes that were removed in the mutant are necessary in maintaining RNA quality and keeping the viability of E. coli cells. Under normal conditions the wild type showed the greatest growth rate with the mutant type following at a significantly lower growth rate which indicates the two genes pnp and pap are responsible for growth of the bacteria, probably due to their roles in normal RNA turnover as described previously. The doubling times of WT and mutant cultures under normal condition are estimated to be about 26 minutes and 48 minutes, respectively. When TBHP was added, the growth rates of both the wild and the mutant types were mostly halted with the wild type keeping a slightly higher growth rate overall in comparing with mutant type.