Biological and biotechnological evaluation of carbon dynamics in field experiments

Abstract

Bacteria and fungi play a key role in promoting soil organic matter (SOM) turn over and consequent nutrient availability to plants uptake. During SOM degradation, they contribute to transform highly complex biomolecules to smaller compounds, which are either immobilized by soil microflora or self-associated in humified and microbially stable superstructures. These processes rapidly occur in the rhizosphere where soil adheres to plant roots and microbial populations are more abundant and active than in bulk soil. Despite the difficulties in determining the composition of soil microbial communities, their genetic and functional diversities are fundamental to maintain soil quality and productivity, even under environmental stress or alteration. Within the national MESCOSAGR project, we provided indications on the composition and diversity of bacterial communities in soils subjected to carbon sequestration treatments. Nucleic acids were extracted from rhizosphere and bulk soils, purified and amplified by polymerase chain reaction (PCR), targeting a conserved region of 16S rRNA gene. Amplicons were separated by denaturing gradient gel electrophoresis (DGGE) and cluster analysis of relative electrophoretic profiles was used to evaluate the diversity of bacteria communities in soils under different soil management practices. The PCR products have also been cloned and sequenced in order to identify and characterize the microbial groups and species which populated the experimental soils. Our results, relative to field trials of the first 2 years and three experimental sites, indicate that the application of different molecular approaches contribute to reach an advanced characterization of structure and diversity of soil bacteria, as well as an appraisal of their variation, as a consequence of specific soil management practices. In particular, it appears that only the amendments with mature compost had a significant effect on the soil microbial communities, while other soil treatments such as that with the iron-porphyrin biomimetic catalyst did not have any effect.