Soil Microbial Communities and Related Functions

This chapter discusses the functions of soil microbial communities. Soil microbial communities and related functions are studied under the constraints of agricultural land use in general and the specific aspects of Research Station Scheyern in particular. Soil microbial communities play an important role in agroecosystem functioning and on the field scale, are essential for plant nutrition and health. They contribute to global element cycling. They are involved in turnover processes of organic matter, breakdown of xenobiotics and formation of soil aggregates. In contrast to plant diversity, and the macro and meso fauna, the aspect of soil microbial diversity is a rather new approach. A major problem in soil microbial analysis has been that most soil microorganisms cannot be characterized by classical microbiological cultivation techniques. Cultivation-independent techniques became more frequent at the beginning of the last decades, leading to a broader view of microbial life in soil. Cultivation-independent molecular approaches are based on the direct extraction of DNA from soil and on subsequent analysis molecular marker genes. Apart from structural genetic analyses, soil microbial communities can also be studied in terms of their in situ functions by means of molecular techniques. The phospholipid approach is another cultivation-independent technique for the analysis of the structural diversity of soil microorganisms. Phospholipids are essential components of membranes of all living cells, and their fatty acid or ether-linked isoprenoid side chains allow a taxonomic differentiation within complex microbial communities. This approach is now well established in soil ecology and serves as a phenotypic and a complementary tool to genotypic (molecular genetic) approaches.