Methylglyoxal and other carbohydrate metabolites induce lanthanum-sensitive Ca2+ transients and inhibit growth in E. coli

The results here are the first demonstration of a family of carbohydrate fermentation products opening Ca2+ channels in bacteria. Methylglyoxal, acetoin (acetyl methyl carbinol), diacetyl (2,3 butane dione), and butane 2,3 diol induced Ca2+ transients in Escherichia coli, monitored by aequorin, apparently by opening Ca2+ channels. Methylglyoxal was most potent (K1/2=1mM, 50mM for butane 2,3 diol). Ca2+ transients depended on external Ca2+ (0.1–10mM), and were blocked by La3+ (5mM). The metabolites affected growth, methylglyoxal being most potent, blocking growth completely up to 5h without killing the cells. But there was no affect on the number of viable cells after 24h. These results were consistent with carbohydrate products activating a La3+-sensitive Ca2+ channel, rises in cytosolic Ca2+ 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.