Calcium and the hormone-like regulation of metabolism in the bacterium Azospirillum brasilense

Calcium ion is known to act as an effector of signal transducing systems in eukaryotes; ifs physiological role in prokaryotes is presumably connected with cell response on environmental stimuli. It is found that wheat lectin (wheat germ agglutinin, WGA), which is known to be able to influence animal cells similarly to the hormone insulin, also exerts a hormone-like action on metabolism of the plant-associated bacterium Azospirillum brasilense. To test whether Ca2+ content in A. brasilense changes after binding of the le ctin to the bacterium, WGA-activated and non-activated azospirillum cells w ere compared regarding the Ca2+ content using flame atomic absorption spect rometry. Lectin-activated cells were found to have 11.4% less Ca2+ than the non-activated bacteria. The results obtained support the assumption that t he activation of metabolism. with wheat lectin is calcium-dependent, and Ca 2+ is suggested to be involved in the pleiotropic response of A. brasilense to WGA.