Development of New reporter systems for studying gamma butyrolactone mediated signaling in streptomyces

Abstract

Streptomyces are saprophytic bacteria ubiquitous in soil and well-known as producersof two-thirds of clinically used antibiotics. Antibiotic production and in some cases morphological differentiation is regulated by population density dependent signaling. Among the signaling molecules that have been identified, gamma butyrolactones (GBLs) form the major class. GBLs are small diffusible molecules which function at nanomolar concentrations and three major structural types are known. Due to limited quantities of GBLs produced, the traditional approach of isolation and structure determination followed by the study of functional roles is challenging. The development of two new receptor based reporter systems for A-factor and Virginiae Butanolide type GBLs is reported here. Together with a previously developed reporter for SCB type GBLs, these reporters can be utilized for screening environmental samples and pure compounds for signaling activity and for studying the specificity of various GBL signal-receptor systems among Streptomyces and to identify potential new signaling molecules. The reporters also serve as valuable tools in the study of GBL signal based communication between Streptomyces and other species and contribute towards a broader understanding of the role of signaling in Streptomyces ecology and evolution. Even though the development of fully functional reporters could not be completed, this study provides valuable insight into the many issues associated with developing Streptomyces based reporter systems. Modifications to the reporter system that may address these issues are discussed. Further, results from preliminary studies conducted for developing high throughput methods for screening signaling activity among Streptomyces isolates are also reported.