Exploring the potential of microcalorimetry to study soil microbial metabolic diversity

Microcalorimetry and BIOLOG are common tools in the study of soil microbial metabolism. When used combined, they may reveal further details about soil microbial metabolic diversity than individually. Through this study, we demonstrated the advantages of such a combinatorial methodology by comparing soil samples from two locations in China, each with (OM samples) and without (control) organic fertilization. We used BIOLOG and microcalorimetry to study soil microbes’ ability to metabolize different C substrates. Microcalorimetric measurements helped us further reveal the differences in the microbial growth kinetics under different BIOLOG-identified C substrates. Results showed that soils differed in the preferred C substrates, as denoted by the thermodynamic parameters. Some C substrates stimulated the active microbial biomass, while some stimulated microbial growth rate. Most interestingly, certain C substrates (e.g., l-arginine for Shandong soil and glycogen for Henan soil) showed stimulating effects on both OM and control soils, which could be attributed to the pH value and P availability in soil. Hence, we believe microcalorimetry could be potentially used to explore the soil microbial metabolic diversity by combining BIOLOG measurement, especially in determining how microbes assimilate different nutrient sources.