Substrate Utilization Patterns of Extractable and Non-Extractable Bacterial Fractions in Neutral and Acidic Beech Forest Soils

Abstract

Substrate utilization patterns of four neutral and four acidic beech forest soils were examined using BIOLOG GN microplates. Soil bacteria were extracted using a three batch fractionated centrifugation procedure that produces two fractions. One contains the extracted and one the non-extractable bacteria and the fungi. Substrate utilization patterns of both fractions were determined with inhibition of fungal growth. All samples cluster distinctly into four different groups which correspond to the two fractions of the acidic and the neutral soils. Bacteria in acidic soils have generally a lower overall colour development indicating lower utilization activity. The extracted bacteria from acidic soils show a lower functional diversity than those extracted from neutral soils, but no difference in diversity was observed when the results of the extracted and the non-extractable bacteria of each soil were combined. In acidic soils substrate utilization abilities are heterogenously distributed between the two fractions. This effect mainly occurs in carbohydrate utilization. Bacterial communities in acidic soils are especially unable to degrade carboxylic acids. As decarboxylation is a main process of the initial decomposition of organic residues, this inability may be one reason for the retarded degradation of freshly fallen litter in acidic soils.