Solventogenic clostridia possess high biotechnological impact due to their ability to produce biobutanol. Nevertheless these obligate anaerobes exhibit only a limited number of molecular tools for specific modification of gene expression. Thus in this work a novel fluorescence-based in vivo reporter system, which is based on oxygen-independent fluorescence proteins (FbFPs) was established for the model organism Clostridium acetobutylicum. The fluorescence was optimized concerning growth-physiological and molecular criteria. Furthermore a protocol for characterization of clostridial promoter activities was developed. Macro- and microscopic fluorescence-demonstrations of recombinant C. acetobutylicum-strains confirmed the functionality of this system. Moreover the applicability of the novel in vivo reporter system was verified by promoter studies of four native C. acetobutylicum genes (thlA, ptb, adc, hydA). Beside this the growth-dependent characterization of the adhE2-promoter revealed a derepressed activity in different C. acetobutylicum integrationmutants with “ethanologenic” phenotype compared to the wildtype. In addition an inducible system for specific gene expression and a fluorescence-based high-throughput screening was developed for C. acetobutylicum. The results demonstrated the effectiveness of this fluorescence reporter system to differentiate between promoter strength and growth-dependent profiles.