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Abstract

Microsensors are powerful tools for the determination of local fluxes and the distribution of microbial activity in sediments, microbial mats, biofilms, aggregates and other immobilized cell systems (ICS). Within these structures free convection is hindered, and consequently mass transfer to the cells often limits conversion rates. Determination of the microbial community using microbiological or molecular methods have obvious limitations for predictions of the behavior of the ICS. Firstly, any enumeration method, both the cultivation dependent and molecular methods have biases. Prediction of the behavior of immobilized biomass based on these enumerations are further biased by the unknown species distribution within the ICS. Because of mass transfer resistance the microenvironment in the ICS differs from the bulk medium. Consequently, extrapolation of the system behavior to that of the cells is impossible without knowledge about their microenvironment. Therefore, detection techniques with high spatial resolution are needed, both for microbial species and microbial activity distribution. New tools are molecular analyses of the genetic material, avoiding the bias of cultivation methods, and the use of microelectrodes to determine the chemical composition inside intact ICS.