Abstract
The direct total count of bacteria and the concentration of isoprenoid quinones were measured in 82 samples from different aquatic and soil environments. The geometric mean of the total count (TC)/total quinine (TQ) ratios obtained with different environments ranged from 1.1 to 2.2×103 cells fmol-1. When the concentration of the total respiratory quinone (TRQ), i.e., ubiquinones and menaquinones, were taken into account, the geometric mean of the TC/TRQ ratios fell into a range of 2.2 to 4.1×103 cells fmol-1. A high positive correlation was noted between TC and TQ (r2=0.9864) or TRQ (r2=0.9990). Based on the relationship between TC and TRQ, 1 nmol of the total quinone was estimated to be equivalent to 2.5×109 cells of bacteria on average. These results indicate that the concentration of the respiratory quinones can be used as a good measure of bacterial counts and biomass in the environment.
