Screening of a highly soluble and oxygen-independent blue fluorescent protein from metagenome

► We here screen a blue fluorescent protein, named mBFP, from metagenomic DNA. ► This protein shows an oxygen-independent fluorescence. ► Thus, the protein could be used to image live cells under anaerobic conditions. ► The fluorescence of mBFP is dependent on the binding of NADPH. ► Thus, mBFP could also be used to measure viability or metabolic activity of cells.