%0 Journal Article %T Real-time determination of intracellular oxygen in bacteria using a genetically encoded FRET-based biosensor %A Janko Potzkei %A Martin Kunze %A Thomas Drepper %A Thomas Gensch %A Karl-Erich Jaeger %A Jochen B¨¹chs %J BMC Biology %D 2012 %I BioMed Central %R 10.1186/1741-7007-10-28 %X We developed a genetically encoded F£¿rster resonance energy transfer (FRET)-based biosensor allowing the observation of changing molecular oxygen concentrations inside living cells. This biosensor named FluBO (fluorescent protein-based biosensor for oxygen) consists of the yellow fluorescent protein (YFP) that is sensitive towards oxygen depletion and the hypoxia-tolerant flavin-binding fluorescent protein (FbFP). Since O2 is essential for the formation of the YFP chromophore, efficient FRET from the FbFP donor domain to the YFP acceptor domain only occurs in the presence but not in the absence of oxygen. The oxygen biosensor was used for continuous real-time monitoring of temporal changes of O2 levels in the cytoplasm of Escherichia coli cells during batch cultivation.FluBO represents a unique FRET-based oxygen biosensor which allows the non-invasive ratiometric readout of cellular oxygen. Thus, FluBO can serve as a novel and powerful probe for investigating the occurrence of hypoxia and its effects on a variety of (patho)physiological processes in living cells.Non-invasive detection of intracellular O2 is of particular importance since it is one of the key metabolites of obligate and facultative aerobic organisms. Cellular O2 is a prominent indicator for oxygen-dependent metabolic activities, such as aerobic respiration or oxygen dependent synthesis and degradation of cellular components [1,2]. In addition, various biological, pathological and biotechnological processes are controlled by O2 limitation, including biofilm formation and host-pathogen interactions [3-7], hypoxia induced inflammatory processes [8], tumor pathophysiology [9-12] as well as microbial fermentation processes used for bioremediation and the production of food, feed and biofuels [13-16].To date, different minimally invasive fluorescence and phosphorescence based O2-sensitive probes have been developed for imaging molecular oxygen in cells and tissues. Among them, platinum(II)-porphyrin dyes a %U http://www.biomedcentral.com/1741-7007/10/28