Identification and characterization of the mre gene region of Streptomycescoelicolor A3(2)

During a search for new differentiation factors in Streptomyces coelicolor A3(2), a locus at 11 o'clock on the S. coelicolor map was identified which harbours several genes that show extensive similarity to cell division and differentiation genes from Escherichia coli and Bacillus subtilis. From the sequence data it was concluded that the region contains the genes mreB, mr eC, mreD (murein formation gene cluster E), pbp83 (high-molecular-weight pe nicillin-binding protein) and sfr (member of the spoVE/ftsW/rodA family). M re gene products are reported to be responsible for determining cell shape in E. coli and Bacillus. The S. coelicolor mreC gene was inactivated by gen e disruption, resulting in mutants which showed significant growth retardat ion in comparison to the wild type. Inactivation of the mreB gene was incom patible with viability, and thus mreB represents a Streptomyces cell divisi on gene that is essential for survival. Promoter-probe experiments led to t he identification of an operon structure, with promoters located upstream o f mreB, pbp83 and sfr. Detailed studies of mreB transcription revealed the existence of three promoters; two of them are constitutively transcribed, w hereas the third is developmentally regulated.