Analysis of microbial communities with electrochemical microsensors and microscale biosensors.

Electrochemical microsensors for O2, pH, H2S, H2, and N2O are now available commercially, thus it has become a relatively simple task to analyze the microenvironment in stratified microbial communities for several chemical species. In addition, sensors are available for the physical parameters diffusivity and flow, and based on knowledge about both transport processes and microdistribution of chemistry, it becomes possible to calculate the spatial distribution and local rates of transformations, such as aerobic respiration or denitrification. As compared to other advanced techniques, microsensor equipment is inexpensive. For example, it is possible to start working with oxygen microsensors with an investment of only about 5000 dollars. Construction of one's own microsensors is only recommended for the very dedicated user, but the investment here is mainly in terms of man-hours as the equipment is simple and inexpensive. By establishing a microsensor construction facility, it is possible to work with short-lived sensors such as ion-selective microsensors for H+, NO2(-), NO3(-), Ca2+, and CO3(-) based on ion exchangers and with microscale biosensors for NO(x)-, NO2(-), CH4, and volatile fatty acids based on immobilized bacteria.