Kinetics, diffusional limitation and microscale distribution of chemistry and organisms in a CANON reactor.

In the Completely Autotrophic Nitrogen removal Over Nitrite (CANON) process, aerobic and anaerobic ammonia oxidizing bacteria cooperate to remove ammonia in one oxygen-limited reactor. Kinetic studies, microsensor analysis, and fluorescence in situ hybridization on CANON biomass showed a partial differentiation of processes and organisms within and among aggregates. Under normal oxygen-limited conditions ( approximately 5 microM O2), aerobic ammonia oxidation (nitrification) was restricted to an outer shell (<100 microm) while anaerobic ammonia oxidation (anammox) was found in the central anoxic parts.

Pericellular oxygen depletion during ordinary tissue culturing, measured with oxygen microsensors.

Recent research has found important differences in oxygen tension in proximity to certain mammalian cells when grown in culture. Oxygen has a low diffusion rate through cell culture media, thus, as a result of normal respiration, a decrease in oxygen tension develops close to the cells. Therefore, for the purpose of standardization and optimization, it is important to monitor pericellular oxygen tension and cell oxygen consumption.

Bacterium-based NO2- biosensor for environmental applications.

A sensitive NO2- biosensor that is based on bacterial reduction of NO2- to N2O and subsequent detection of the N2O by a built-in electrochemical N2O sensor was developed. Four different denitrifying organisms lacking NO3- reductase activity were assessed for use in the biosensor. The relevant physiological aspects examined included denitrifying characteristics, growth rate, NO2- tolerance, and temperature and salinity effects on the growth rate.

Microscale biosensor for measurement of volatile fatty acids in anoxic environments.

A microscale biosensor for acetate, propionate, isobutyrate, and lactate is described. The sensor is based on the bacterial respiration of low-molecular-weight, negatively charged species with a concomitant reduction of NO(-)(3) to N(2)O. A culture of denitrifying bacteria deficient in N(2)O reductase was immobilized in front of the tip of an electrochemical N(2)O microsensor.