Use of red autofluorescence for monitoring prodiginine biosynthesis

• Red fluorescence and red pigmentation were compared to assess prodiginine production.
• The red autofluorescence of S. coelicolor is strictly associated with prodiginines.
• Fluorescence-based methods are more sensitive than colorimetric-based methods.
• Fluorescence-based methods allow in situ time–space visualization of prodiginines.

Prodigiosin-like pigments or prodiginines (PdGs) are promising drugs owing to their reported antitumor, antibiotic, and immunosuppressive activities. These natural compounds are produced by several bacteria, including Streptomyces coelicolor and Serratia marcescens as most commonly studied models. The bright red color of these tripyrrole pigments made them excellent reporter molecules for studies aimed at understanding the molecular mechanisms that control secondary metabolite production in microorganisms. However, the natural red fluorescence of PdGs has only been rarely used as a biophysical parameter for detection and assessment of PdG biosynthesis. In this work, we used S. coelicolor in order to exemplify how intrinsic red fluorescence could be utilized for rapid, low-cost, sensitive, specific and accurate semi-quantitative analyses of PdG biosynthesis. Additionally, and contrary to the colorimetric-based approach, the fluorescence-based method allows in situ spatio-temporal visualization of PdG synthesis throughout a solid culture of S. coelicolor. As PdG production is related to cell differentiation, their red autofluorescence could be exploited, by means of confocal microscopy, as a natural marker of the entrance into a crucial developmental stage in the course of the S. coelicolor life cycle.