Effect of arsenate on chemotactic behavior of Escherichia coli

Escherichia coli cells treated with arsenate cannot tumble. The relationship between cellular adenosine 5'-triphosphate (ATP) level and the ability to tumble has been studied. (i) Cells incubated with arsenate completely lost their tumbling ability, and the cellular ATP level was decreased to less than 0.3 nmol/mg of protein. (ii) Incubation with 10 mM arsenate-1 mM phosphate reduced the cellular ATP level to less than 0.25 nmol/mg of protein. However, the cells were still able to tumble. (iii) Tumbling of the arsenate-treated cells was completely recovered after addition of a slight amount of phosphate, although the ATP level was still as low as 0.2 nmol/mg of protein. (iv) The cellular ATP level of an arsenate-treated uncA mutant (Ca2+,Mg2+-adenosine triphosphatase defective) was lower than 0.1 nmol/mg of protein even after the addition of 5 5 mM phosphate. However, tumbling ability was almost completely restored upon addition of the phosphate.