LEAPS-MPS: Determining the Mechanisms by Which Alarmone Signaling in Clostridioides Difficile Differs From Tthat in other Bacteria

Old Dominion University Research Foundation, Norfolk VA

Investigators

Abstract

With the support of the Mathematical and Physical Sciences Directorate and the Division of Chemistry, Professor Erin B. Purcell and her group at Old Dominion University will study nucleotide signal molecules known as ‘alarmones.’ Bacteria across diverse types respond to environmental stress by synthesizing different chemical species, such as tetraphosphate and pentaphosphate alarmones, to regulate survival mechanisms. Until recently, smaller triphosphate alarmones were thought to be degradation products of the larger signal molecules. However, it has recently been discovered that some bacteria synthesize triphosphate alarmones directly in addition to the tetra- and pentaphosphate signals. To date, the anaerobic spore-forming bacterium Clostridioides difficile is the only bacterium reported to synthesize triphosphate alarmones exclusively. Graduate and undergraduate trainees in the Purcell lab intend to determine how this organism’s alarmone synthesis and utilization differ from those in other bacteria. This project is expected to expand understanding of alarmone signaling and establish a paradigm for signaling by the triphosphate alarmone alone. This project will provide opportunities to train graduate and undergraduate researchers in foundational biochemistry techniques. Graduate researchers, mostly from underrepresented groups, will also gain experience as co-mentors of undergraduate trainees to nurture their leadership skills as future scientific leaders and role models. The objectives of this project will be to determine the structural basis of this organism’s unique alarmone synthesis and the regulatory role played by the incompletely characterized triphosphate alarmone, pGpp. The Purcell group is especially interested in discovering which active site residues in the clostridial alarmone synthetase enzymes are involved in hydrolyzing phosphate bonds on its nucleotide substrates to generate pGpp. Successful implementation of this project will also determine whether clostridial alarmone hydrolases and alarmone-binding effectors can recognize the larger alarmones produced by nearby bacteria, potentially utilizing alarmones for intercellular and interspecies communication as well as intracellular signaling. This project has the potential to identify the genes and processes regulated by alarmone signaling in C. difficile to determine whether it uses its non-canonical alarmone in a conserved manner or whether the outputs of alarmone signaling pathways in this organism are also unique. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.