Effects of organic antagonists of Ca2+, Na+, and K+ on chemotaxis and motility of Escherichia coli

Various Ca2+ antagonists used in animal research, many of them known to be Ca2+ channel blockers, inhibited Escherichia coil chemotaxis (measured as e ntry of cells into a capillary containing attractant). The most effective o f these, acting in the nanomolar range, was omega-conotoxin GVIA. The next most effective were gallopamil and verapamil. At concentrations around 100- fold higher than that needed for inhibition of chemotaxis, each of these an tagonists inhibited motility (measured as entry of cells into a capillary l acking attractant). Various other Ca2+ antagonists were less effective, tho ugh chemotaxis was almost always more sensitive to inhibition than was moti lity. Cells treated with each of these Ca2+ antagonists swam with a running bias, i.e., tumbling was inhibited. Similarly, some Na+ antagonists used i n animal research inhibited bacterial chemotaxis. E. coli chemotaxis was in hibited by saxitoxin at concentrations above 10(-7) M, while more than 10(- 4) M was needed to inhibit motility. Cells treated with saxitoxin swam with a tumbling bias. in the case of other Na+ antagonists in animals, aconitin e inhibited bacterial chemotaxis 10 times more effectively than it inhibite d motility, and two others inhibited chemotaxis and motility at about the s ame concentration. In the case of K+ antagonists used in animal research, I -aminopyridine blocked E. coil chemotaxis between 10(-3) M and, totally, 10 (-2) M, while motility was not affected at 10(-2) M; on the other hand, tet raethylammonium chloride failed to inhibit either chemotaxis or motility at 10(-2) M.