Lydicamycins Induce Morphological Differentiation in Actinobacterial Interactions

Abstract

Streptomyces are major players in soil microbiomes, however, interactions involving Streptomyces and other actinobacteria are rarely described. The complex developmental cycle of actinobacteria necessitates a multi-omics approach to unravel the web of information. This study resulted from the observation of induced morphogenesis between two environmental isolates from the same site, Kitasatospora sp. P9-2B1 and Streptomyces sp. P9-2B2. When co-cultivated on potato dextrose agar (PDA), P9-2B2 induced a wave-like sporulation in strain P9-2B1. Using mass spectrometry imaging, we revealed that a suite of lydicamycins were present in this induced sporulation zone. Lydicamycin deficient mutants were generated using CRISPR Base-Editing and the inducible sporulation ceased, confirming their role in triggering morphological differentiation. In agar diffusion assays, pure lydicamycin was inhibitory when added concurrently with bacterial inoculation and induced sporulation with delayed addition. Subsequent testing of additional environmental isolates resulted in the same inducible sporulation wave phenomenon, including Streptomyces coelicolor M145 and M1146. Using transcriptomics, we observed the differential expression of genes related to early aerial mycelium development four days into cocultivation and the transitional genes responsible for development of spores on day 9. Along with these differentially expressed genes, we also observed numerous overall stress responses, specifically cell envelope stress responses. These findings uncovered actinobacteria interactions mediated by lydicamycins, pointing to a potential role of certain groups of bioactive metabolites in nature. ImportanceShifting away from an antibiotic discovery mindset, uncovering the chemical ecology of secondary metabolites is key to maximizing their biotechnological application. The reduced complexity of dual cultures allows for in depth analysis and investigation of these interactions via multi-omics provides orthogonal data leading to more robust conclusions. This study provides insight into the role of lydicamycins in dual cultures with other actinobacteria and provides an integral roadmap for future chemical ecology work between microorganisms, especially through the use of mass spectrometry imaging.