Abstract
The kinetics of L-alanine-induced spore germination of Bacillus subtilis was studied in a very low range (<6μM) of concentration of L-alanine (ALA), where departure from Michaelis-Menten kinetics is frequently observed. For this purpose, a very sensitive method for measuring germination was devised based on the fact that a DNA repair-deficient mutant, UVSSP42-1, produces spores extremely sensitive to ultraviolet (UV) radiation, and the spores acquire normal UV resistance upon germination. After UV irradiation at an appropriate fluence, germination percentage was calculated from the survival of spores. Germination as low as 0.1% could be measured with sufficient accuracy for kinetic analysis. In a range of ALA concentration of 1.75 to 6μM, a double logarithmic plot of germination rate against ALA concentration gave a straight line with a slope of about 3. It may be assumed that binding of three molecules of ALA per receptor is required to trigger germination.
