Effect of root exudates in microbial diversity and activity in rhizosphere soils

The rhizosphere is the soil volume at the root-soil interface that is under the influence of the plant roots and the term was introduced by Hiltner in 1904 (Brimecombe et al. 2001). Microbial population in the rhizosphere has continuous access to a flow of low and high molecular weight organic substrates derived from roots. This continuous flow of organic compounds may affect together with specifìc physiochemical and biological conclitions microbial activity and community structure of the rhizosphere soil (Sorensen 1997; Brimecombe et al. 2001). Current techniques still lack the adequate sensitivity ancl resolution for data collection at the micro-scale, and the question 'How important are various soil processes acting at different scales for ecological function?' is therefore challenging to answer. The nano-scale secondary ion mass spectrometer (NanoSIMS) represents the latest generation of ion microprobes, which link high-resolution microscopy with isotopic analysis. Recently, Herrmann et al. (2007) have describecl the principles of NanoSIMS and discusses the potential of this tool to contribute to the field of bio-geochemistry and soil ecology.