Streptomyces coelicolor: DNA methylation and differentiation - Palermo 27-06-2014

DNA methylation is an epigenetic modification regulating many aspects of biological processes. DNA cytosine methylation plays mainly a regulatory role in chromatin organization, genome maintenance and gene expression in eukaryotes, while its role has not been deeply investigated in prokaryotes. Differently, DNA adenine methylation regulates chromosome replication, DNA repair, transposition of insertion elements in prokaryotes, while it is supposed to have exclusively a role in regulating gene expression and DNA replication in mitochondria. Streptomyces coelicolor is a soil-dwelling Gram-positive bacterium that exhibits a complex life cycle, with three different cell types (unigenomic spores, aerial and vegetative hyphae) and two events of programmed cell death, and produces three antibiotics. The aim of this project is to correlate DNA methylation with morphological and physiological differentiation of S. coelicolor. Dot blot analysis revealed that the global level of methylated cytosines and adenines changes during growth in liquid medium. The characterization of cytosine methylome, by Bisulphite-sequencing, revealed that 30% of S. coelicolor genes contain a AAGCCmCG or TGGCmCGGC motif in their upstream regions. Among these, genes related to differentiation, DNA repair and condensation were found. Treatment with 5-aza-2’-deoxycytidine, a hypomethylating agent, showed that DNA methylation influences growth and antibiotic production both in liquid and on solid culture. These results suggest a role for DNA cytosine methylation in morphological and physiological differentiation of S. coelicolor. Further experiments are ongoing to demonstrate if it has a role in regulating gene expression and/or in activating cell death events.