The regulation of development in the antibiotic-producing bacteria Streptomyces (BUTTNER_J17DTP)

Lead Research Organisation: University of East Anglia
Department Name: Graduate Office

Abstract

Streptomycetes are filamentous bacteria that grow by tip extension and branching to form a vegetative mycelium. Nutrient depletion triggers a developmental program that leads to the formation of specialized reproductive structures called aerial hyphae, which ultimately give rise to long chains of spores. This program is genetically and temporally coordinated with the production of numerous commercially important antibiotics (Streptomycetes account for $40 billion of revenue annually in the pharmaceutical industry worldwide). The transition from vegetative growth to the formation of aerial hyphae is controlled by a regulatory switch consisting of a sigma factor, BldN, and its cognate anti-sigma, RsbN, a transmembrane protein. After BldN is expressed, it is held inactive by RsbN, which sequesters it to the membrane, until an unknown signal triggers Regulated Intramembrane Proteolysis (RIP) of RsbN and release of BldN into the cytoplasm. The goals of this project are to identify the signal that triggers release of BldN and to characterize the proteolytic process that inactivates RsbN.

Bibb, M.J., Domonkos, Á., Chandra, G., and Buttner, M.J. (2012) Expression of the chaplin and rodlin hydrophobic sheath proteins in Streptomyces venezuelae is controlled by BldN and a cognate anti-sigma factor, RsbN. Mol. Microbiol. 84:1033-1049.

Bush, M.J., Tschowri, N., Schlimpert, S., Flärdh, K., and Buttner, M.J. (2015) c-di-GMP signalling and the regulation of developmental transitions in streptomycetes. Nature Rev. Microbiol. 13:749-760.

Tschowri, N., Schumacher, M.A., Schlimpert, S., Chinnam, N.B., Findlay, K.C., Brennan, R.G., and Buttner, M.J. (2014) Tetrameric c-di-GMP mediates effective transcription factor dimerization to control Streptomyces development. Cell 158:1136-1147.

Publications

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Description The classical life cycle of Streptomyces is intricate, involving the generation of distinct developmental structures in response to environmental cues - the vegetative mycelium, the hydrophobic aerial hyphae, and mature spores. The production of clinically useful antibiotics is tightly coordinated with this complex life cycle.

Two families of developmental regulators control the life cycle transitions in Streptomyces. Bld regulators control the formation of the reproductive aerial hyphae, while Whi regulators control the differentiation of the reproductive structures into spores. My work focused on BldB, whose function was a mystery. BldB has ten paralogues in Streptomyces venezuelae, all of which are encoded next to paralogues of the DNA-binding regulator WhiJ. Five of these BldB paralogues are encoded next to paralogues of the putative anti-sigma factor AbaA. I showed that the deletion of bldB in S. venezuelae leads to a classical "bald" phenotype - the mutant cannot differentiate past vegetative growth. In contrast to some suggestions in existing literature, I did not find any evidence that BldB is a transcription factor - it did not bind DNA in ChIP-seq and SPR experiments. By screening a bacterial-two-hybrid library, I demonstrated that BldB strongly interacts with seven of its S. venezuelae BldB paralogues. The deletion of two of these paralogues results in sporulation-deficient phenotypes in S. venezuelae. RNA-seq showed a striking upregulation of all five abaA paralogues and the novel inhibitor of sporulation iosA in the ?bldB mutant, suggesting that BldB indirectly represses the expression of these genes. I showed that the tandem overexpression of abaA6 and iosA recapitulates the ?bldB mutant phenotype. The putative anti-sigma factor AbaA6 is involved in a network of protein interactions reminiscent of SigB-like partner-switching systems. I demonstrated that one of the WhiJ paralogues, WhiJ9, directly activates the expression of iosA by binding to direct repeats in the iosA-whiJ9 intergenic region.
Exploitation Route The outcomes of this award would be most useful in education and further scientific research, as the undertaken research work is mostly of a fundamental nature. However, there is a connection between the developmental life cycle of Streptomyces, and their striking ability to produce various secondary metabolites, which are widely used in medicine, so it is possible that the results of this PhD could inform future work related to production of novel pharmaceutical products.
Sectors Education,Pharmaceuticals and Medical Biotechnology,Other
 
Description Art and Science Workshop 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Schools
Results and Impact 30 students attended an Art and Science Workshop organised by UEA and the Sainsbury Centre for Visual Arts. I was the scientist for this workshop, and I worked with 2 artists to design activities under the theme "Who is fighting under my feet?" aimed at explaining the bigger picture of my research to students. We had two art activities revolved around the information I presented to the students, visualising concepts, such as antibiotic resistance. The students were very active and engaged well, with a surprising level of scientific knowledge.
Year(s) Of Engagement Activity 2020