PROJECT SUMMARY In all domains of life, cells must employ tightly controlled mechanisms to regulate global processes in response to environmental inputs. In bacteria, signaling through the nucleotide second messenger 3’,5’-cyclic diguanylic acid (c-di-GMP) is one of the most conserved mechanisms cells use to trigger lifestyle changes in response to specific environmental cues. Although the enzymes that synthesize and degrade c-di-GMP can be found in all bacterial phyla, studies of this second messenger have focused on model species belonging to the Phylum Pseudomonadota. A key knowledge gap is understanding how this fundamental mechanism governs regulation of gene expression in diverse bacterial phyla. This project will address this by characterizing the molecular mechanisms and evolution of c-di-GMP signaling in the antibiotic-producing bacterial genus Streptomyces, which belongs to Phylum Actinobacteria (synonym Actinomycetota). In Streptomyces, c-di-GMP is the central integrator controlling a highly unusual life cycle that involves progression from vegetative growth to production of reproductive aerial hyphae that differentiate into chains of spores. To investigate the molecular basis and functional diversification of c-di-GMP signaling, this project will focus on three areas: (1) the mechanisms through which c-di-GMP regulates progression through the developmental life cycle in the model species Streptomyces venezuelae; (2) the evolution and distribution of conserved components of c-di-GMP signaling networks; and (3) the impact of c-di-GMP on antibiotic biosynthesis, which is tightly controlled along with the developmental life cycle, in diverse antibiotic-producing actinobacterial species. These studies will contribute to a fundamental understanding of how bacterial control gene expression and will leverage this knowledge to manipulate antibiotic production.

PROJECT NARRATIVE The bacterial genus Streptomyces are our most important source of clinical antibiotics, which they produce concomitant with a tightly regulated developmental life cycle that culminates in sporulation. This project will characterize the key molecular mechanisms that underlie control of development in these bacteria and will examine how these mechanisms have evolved. These studies will increase our fundamental understanding of how bacteria regulate gene expression and antibiotic production.