Two-component signal transduction systems in Streptomyces and related organisms studied using DNA comparative microarray analysis

The Conserved Actinobacterial Two-Component System MtrAB Coordinates Chloramphenicol Production with Sporulation in Streptomyces venezuelae NRRL B-65442

Streptomyces bacteria make numerous secondary metabolites, including half of all known antibiotics. Production of antibiotics is usually coordinated with the onset of sporulation but the cross regulation of these processes is not fully understood. This is important because most Streptomyces antibiotics are produced at low levels or not at all under laboratory conditions and this makes large scale production of these compounds very challenging. Here, we characterize the highly conserved actinobacterial two-component system MtrAB in the model organism Streptomyces venezuelae and provide evidence that it coordinates production of the antibiotic chloramphenicol with sporulation. MtrAB are known to coordinate DNA replication and cell division in Mycobacterium tuberculosis where TB-MtrA is essential for viability but MtrB is dispensable. We deleted mtrB in S. venezuelae and this resulted in a global shift in the metabolome, including constitutive, higher-level production of chloramphenicol. We found that chloramphenicol is detectable in the wild-type strain, but only at very low levels and only after it has sporulated. ChIP-seq showed that MtrA binds upstream of DNA replication and cell division genes and genes required for chloramphenicol production. dnaA, dnaN, oriC, and wblE (whiB1) are DNA binding targets for MtrA in both M. tuberculosis and S. venezuelae. Intriguingly, over-expression of TB-MtrA and gain of function TB- and Sv-MtrA proteins in S. venezuelae also switched on higher-level production of chloramphenicol. Given the conservation of MtrAB, these constructs might be useful tools for manipulating antibiotic production in other filamentous actinomycetes.

Microarray-based comparison of genetic differences between strains of Streptomyces turgidiscabies with focus on the pathogenicity island

The areas of the pathogenicity island (PAI) designated as 'colonization region' (CR) and 'toxicogenic region' (TR) [Lerat et al. (2009) Mol. Plant Pathol. 10, 579-585] contain genes required for virulence and phytoxin production, respectively, in Streptomyces spp. causing common scab on potatoes. The PAI was tested for genetic variability by microarray analysis in strains of S. turgidiscabies isolated from potatoes in Finland. The data revealed four types of PAI based on divergent CR and TR which occurred in different combinations. Only one PAI type was highly similar to S. scabies (strains 87.22 and ATTC49173). Using probes designed for the predicted genes of S. scabies, two gene clusters in S. scabies appeared to be similar to most strains of S. turgidiscabies and contained PAI genes corresponding to CR and TR. They were located approximately 5 Mb apart in the S. scabies genome, as compared with only 0.3 Mb in S. turgidiscabies Car8. Data from comparative genomic hybridization with probes designed for S. scabies genes and for the PAI of S. turgidiscabies were compared by multilocus cluster analysis, which revealed two strains of S. turgidiscabies that were very closely related at the whole-genome level, but contained distinctly different PAIs. The type strain of S. reticuliscabiei (DSM41804; synonymous to S. turgidiscabies) was clustered with S. turgidiscabies. Taken together, the data indicate wide genetic variability of PAIs among strains of S. turgidiscabies, and demonstrate that PAI is made up of a mosaic of regions which may undergo independent evolution.