Methylglyoxal and other carbohydrate metabolites induce lanthanum-sensitive Ca 2+ transients and inhibit growth in E. coli

Abstract

The results here are the first demonstration of a family of carbohydrate fermentation products opening Ca 2+ channels in bacteria. Methylglyoxal, acetoin (acetyl methyl carbinol), diacetyl (2,3 butane dione), and butane 2,3 diol induced Ca 2+ transients in Escherichia coli, monitored by aequorin, apparently by opening Ca 2+ channels. Methylglyoxal was most potent ( K 1/2 = 1 mM, 50 mM for butane 2,3 diol). Ca 2+ transients depended on external Ca 2+ (0.1–10 mM), and were blocked by La 3+ (5 mM). The metabolites affected growth, methylglyoxal being most potent, blocking growth completely up to 5 h without killing the cells. But there was no affect on the number of viable cells after 24 h. These results were consistent with carbohydrate products activating a La 3+-sensitive Ca 2+ channel, rises in cytosolic Ca 2+ possibly protecting against certain toxins. They have important implications in bacterial-host cell signalling, and where numbers of different bacteria compete for the same substrates, e.g., the gut in lactose and food intolerance.