A variant, Cig-1 (calcium independent growth) was selected from L-form NC7 culture belonging to the genus Escherichia coli K-12. The Cig-1 differed from the parental L-form NC7 strain in growth response to calcium content . Growth of the L-form NC7 was markedly inhibited by addition of EGTA (1mM) , while Cig-1 was able to grow in the presence of EGTA. When the Cig-1 was transfered to growth medium containing 10μM Ca ionophore, A 23187, the cells did not grow, but E. coli cells were able to grow under the same conditions. When 10 μM of carbonyl cyanide-m-chlorophenylhydrazone (CCCP), a protonophore, was added to growth medium containing glucose at pH 7.5, growth of the Cig-1 was completely blocked, suggesting that proton motive force is requsired for growth of the Cig-1 strain.