fa Molecular Microbiology Molecular Microbiology Study Break Study Break <p><strong>Background:</strong> Improved cyan fluorescent protein (ICFP) is a monochromic, green fluorescent protein (GFP) derivative produced by <em>Aequorea macrodactyla</em> in a process similar to GFP. This protein has strong absorption spectra at wavelengths 426-446 nm. ICFP can be used in cell, organelle or intracellular protein labeling, investigating the protein-protein interactions as well as assessing the promoter activities. <strong>Methods:</strong> In our previous study, the promoters of two chitinases (ChiS and ChiL) from <em>Bacillus pumilus</em> SG2 were assessed in <em>B. subtilis </em>and their regulatory elements were characterized. In the present study, <em>icfp </em>was cloned downstream of several truncated promoters obtained in the former study, and ICFP expression was evaluated in <em>B. subtilis.</em> <strong>Results:</strong> Extracellular expression and secretion of ICFP were analyzed under the control of different truncated versions of ChiSL promoters grown on different media. Results from SDS-PAGE and fluorimetric analyses showed that there were different expression rates of CFP; however, the UPChi-ICFP3 construct exhibited a higher level of expression and secretion in the culture medium. <strong>Conclusion:</strong> Our presented results revealed that inserting this truncated form of Chi promoter upstream of the ICFP, as a reporter gene, in <em>B. subtilis</em> led to an approximately ten fold increase in ICFP expression.</p> Cyan fluorescent protein, Medical reporter gene, Medical screenable marker, Medicinal Protein Engineering 240 248 http://ibj.pasteur.ac.ir/browse.php?a_code=A-10-1-647&slc_lang=fa&sid=1 Abbas Shali No Department of Industrial and Environmental Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB) , P.O. Box 14155-6343 , Tehran, Iran Garshasb Rigi No Department of Biology, Faculty of Science, Behbahan Khatam Alanbia University of Technology, Behbahan, Khuzestan, Iran Majid Pornour No Medical Laser Research Center, Academic Center for Education, Culture and Research (ACECR), Tehran, Iran Gholamreza Ahmadian Yes Department of Industrial and Environmental Biotechnology, National Institute of Genetic Engineering and Biotechnology (NIGEB) , P.O. Box 14155-6343 , Tehran, Iran