Fig. 1. Frequency distribution of Biolog substrate utilization patterns with sampling time. Patterns of color formation were assigned to one of three categories on the basis of absorbance readings after 0, 24, 48, and 72 h. The three categories were: cases with a prolonged lag phase (white columns); cases with a sigmoidal shape (grey columns); and cases with no apparent lag phase (black columns). Bars indicate standard deviations (n = 16).