The small protein TrpM modulates morpho-physiological differentiation in Streptomyces coelicolor

TrpM, a small protein of 63 amino acids, is encoded by a gene of the trpCMBA locus involved in tryptophan biosynthesis in the model actinomycete Streptomyces coelicolor. Indeed, the trpM knock-out mutant strain is characterized by a delayed growth on minimal medium, smaller aerial hyphae, and reduction of both spore and antibiotic actinorhodin production in comparison with the wild-type strain. These observations are in agreement with proteomic analyses which highlighted a role for TrpM in controlling i) tryptophan production through precursor availability and, thus ii) bacterial growth and morpho-physiological differentiation. To further elucidate the role of TrpM, a S. coelicolor trpM knock-in mutant was constructed through E. coli-S. coelicolor interspecific conjugation using the pIJ8600::trpM integrative plasmid. The trpM knock-in mutant strain, grown on minimal medium, is characterized by a faster differentiation and an increased actinorhodin production yield in comparison to the control strain carrying pIJ8600 vector. Moreover, differential proteomic analysis is ongoing in order to identify differentially represented proteins and their biochemical and molecular functions. Altogether these data further confirm the role of TrpM in modulating morpho-physiological differentiation of S. coelicolor expanding our knowledge on the cellular functions of bacterial small proteins.