Relationships Between Organic Matter Contents and Bacterial Hydrolytic Enzyme Activities in Soils: Comparisons...

Microbial assemblages in terrestrial environments, such as soils, utilize hydrolytic enzymes to function biologically in various environments including for the degradation of organic carbon compounds and cycling of nutrients that eventually contributes to the ecological and agricultural productivity of such environments. In this study, 3 soil types (i.e., sandy, loamy and clayey) with varying characteristics were collected within the premises of Albion College in Michigan, with the goal of comparing the occurrences of indigenous bacterial populations and their respective hydrolytic enzyme activities in the soils. The soils were examined for their organic matter content (% OM), while bacterial abundance was determined by combinations of viable counts and nucleic acid staining, and enzymatic activities measured using fluorescein diacetate (FDA) analysis. Results from the study showed loamy soil to have a significantly higher % OM at 30% on average as compared to 2.5% and 6.6% recorded in the sandy and clayey soils. Comparatively, bacterial numbers (both viable and total counts) were also significantly higher in loamy soils than the other two soils. The same trend was observed for FDA analysis with higher fluorescein released in the loamy soil relative to the two other soils. Overall, clear differences were observed in the relationships between % OM and bacterial numbers and hydrolytic enzyme activities among the three soil types and between the two seasons examined. The results suggest that % OM strongly influences both bacterial abundance and hydrolytic enzyme activities in loamy soil and less so in both sandy and clayey soils examined in the study. This study in conclusion revealed potential strong relationships between soil organic carbon and indigenous bacterial populations as well as their FDA activities in various soil types.