Analysis of respiratory quinones in soil for characterization of microbiota

Method for the analysis of respiratory quinones in soil was developed to characterize soil microbiota. The respiratory quinones were extracted with a mixture of chloroform and methanol using a Wahling blender or a sonicator and cleaned-up by a silicagel column cartridge. The quinone species were determined by reverse-phase high performance liquid chromatography. Spectra of peaks were measured with a photodiode array detector to examine the purity. More than 90% of extractable quinones in soil were recovered by three extractions. The recovery of quinones, added to soil as freeze-dried powder of microorganisms, was higher than 96%. This procedure led to higher representative results as follows. Fluctuations within 95% of cumulative frequency were 13% for the extracted amount of quinones and 20% for the dissimilarity, respectively. The quinone profiles of four soils were determined as follows: a soil from the aerobic layer of a paddy field, an ando soil and two yellow upland soils which had received chemical fertilizers with and without farmyard manure. The quinone profiles displayed clear differences in the microbial composition and in the microbial diversity among the soils. It was demonstrated that the analysis of the respiratory quinone profile was useful to characterize the microbial community structure in soil.