To address the lack of analytical tools for non-invasive, on-line fluorescence determination in growing bacterial cultures, we collaborated with PreSens to develop mSDR, an innovative tool for simultaneous red fluorescence determination in up to 240 growing cultures. We developed, established, and calibrated the system, evaluated its precision and signal detection range. To assess the utility value of the mSDR and investigate the regulation of early clavulanic acid biosynthesis genes in Streptomyces clavuligerus, we designed reporter systems. These systems utilized the mCherry fluorescent protein under the control of the PceaS2 promoter. This promoter corresponds to the region of the ceaS2 gene, which is the first among the early genes in the clavulanic acid biosynthesis cluster. It is well-established that initiating transcription of the ceaS2 gene triggers the transcription of other genes in the cluster. The primary activator for this cluster is CcaR, and its binding site resides on the PceaS2 promoter. Therefore, we posited that increased CcaR regulator activity would lead to enhanced transcription of both the reporter gene and the clavulanic acid cluster genes. Through the monitoring of fluorescence, we can now identify bacterial strains with improved productivity and efficiency. We discovered new potential approaches to enhance production strains and significantly improved productivity of the selected strain. mSDR has proven to be extremely useful for monitoring the activity and regulation of genes involved in important secondary metabolites, as well as selecting potential production strains at the laboratory level. Furthermore, the tool has the potential for various analytical purposes in microbiology and beyond.
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