Using structural biology and biochemistry to study environmental stress sensing by bacterial stressosome complexes

Bacteria must respond to changes in their external environment to survive and thrive. They do this through proteins embedded in their cell membranes, or free in their cells, which sense changes in their physical conditions and the presence of small molecules and ions. These sensors can alter gene expression patterns, or control messenger chemicals, that alter cellular behaviour and allow bacteria to adapt to a changing environment.
The stressosome is a multi-protein complex found in many bacterial species, including the soil bacterium Bacillus subtilis; foodborne pathogen Listeria monocytogenes; and marine pathogen Vibrio vulnificus. The stressosome acts as a signal integration hub made up of sensor proteins and a protein kinase. When the sensor proteins are activated, the signal is transduced to the kinase, which leaves the stressosome and sets off a signalling cascade. The kinase can activate secondary messenger signalling or induce changes in gene expression. Despite its importance to bacterial adaptation and survival, we do not know the exact nature of the activating signals for the stressosome and there have been no structural studies on native stressosomes isolated from their hosts.
This project aims to determine the structure and composition of native stressosomes from Bacillus and Listeria species. It will use a combination of molecular microbiology and protein purification methods to isolate stressosomes. Using single-particle cryo-EM methods and machine learning, the project will determine the structure of the stressosome complexes and build atomic models to understand their structure and function. This will be complemented by structural mass spectrometry, to determine how different environmental conditions affect the composition of the stressosome.
The student will benefit from training in molecular microbiology, protein biochemistry; biophysics; structural bioinformatics; structural biology methods including X-ray crystallography and cryo-EM; and mass...