The mechanism of carbonate killing of Escherichia coli

Aims: To define the mechanism of carbonate killing in Escherichia coli. Methods and Results: Sodium carbonate (150 mM) and ethylenediaminetetraacet ic acid (EDTA, 60 mM) both killed E. coli K-12 when the pH was 8.5, but amm onium chloride (150 mM) was ineffective. EDTA was a 5-fold more potent agen t than carbonate, but some of this difference could be explained by ionizat ion. At pH 8.5, only 1.6% of the carbonate is CO-2, but nearly 100% of the EDTA is EDTA(-2). Conclusions: As carbonate and EDTA had similar effects on viability, cellul ar morphology, protein release and enzymatic activities, the antibacterial activity of carbonate seems to be mediated by divalent metal binding. Significance and Impact of the Study: Cattle manure is often used as a fert ilizer, and E. coli from manure can migrate through the soil into water sup plies. Previous methods of eradicating E. coli were either expensive or env ironmentally unsound. However, cattle manure can be treated with carbonate to eliminate E. coh, and the cost of this treatment is less than $0.03 per cow per day.