Escherichia coli bacteria indicators were prepd. and used for biosynthesis of green fluorescent protein variants. Mutation into gfpuv gene were introduced to obtain protein variants emitting yellow fluorescence and blue fluorescence. Mol. cloning, genetic expression and protein isolation, involving chem. extn. methods and chromatog. were applied and the high biosynthesis levels of recombinant homogeneous fluorescent proteins were achieved. The indicator bacteria and purified proteins were designed for monitoring surfaces cleaning, probiotic bacteria colonization assessment, biochem. industrial processes and environment remediation.