Associate Prof Jani Bolla

Associate Prof Jani Bolla

Louise Johnson Associate Professor of Molecular and Cellular Biochemistry

Molecular mechanisms of membrane transport and biogenesis in double envelope systems

Biological membranes, composed largely of lipids and proteins, allow cells to maintain internal conditions distinct from those of the external environment. In eukaryotes, membranes further enable compartmentalisation and functional specialisation within organelles. Most organelles are enclosed by a single membrane, whereas endosymbiotic organelles, such as mitochondria and chloroplasts, derived from Gram-negative bacteria, retain a double envelope with an outer membrane enriched in β-barrel proteins. This additional barrier increases regulatory complexity and requires coordinated transport and quality control across the envelope while preserving membrane integrity.
 
Our research examines how lipid and protein components are transported across and assembled into the double-envelope membranes of Gram-negative bacteria and chloroplasts. Studying these systems in parallel enables us to distinguish deeply conserved principles from features that have diverged since endosymbiosis.
 
We combine structural mass spectrometry techniques, including native mass spectrometry and hydrogen–deuterium exchange mass spectrometry, with cryo-electron microscopy to resolve envelope machineries in defined functional states and map their dynamics. Much of our work centres on Pseudomonas pathogens, including Pseudomonas aeruginosa and Pseudomonas syringae, alongside the chloroplast envelope from model organisms. We are particularly interested in lipid transport and outer-membrane homeostasis, β-barrel protein assembly, and protein import across envelopes. Together, these studies provide a mechanistic basis for understanding envelope function in bacterial pathogenicity and antibiotic resistance, and for exploring how chloroplast envelopes support organelle function and stress resilience.