Based on this, we thus conclude that our observations are incompatible with lipid-exchange induced transformations. In contrast, several factors hint to a lipase-based mechanism: i) S. aureus expresses extracellular lipases; ii) previous studies have reported similar transformations based on the action of lipase ex vivo and the accumulation of oleic acid in the lipid matrix; iii) phytantriol cubosomes, which cannot be digested by lipase as the lipids lack an ester bond, are unaffected by exposure to the bacteria. Taken together, these results strongly support the mechanism proceeding via the action of Staphylococcal lipases. The effect of overnight incubation with S. aureus on the bulk monoolein mesophase was observed with polarised light microscopy (Figure , Figure ). The transition from V₂→H₂ phase is identified by the formation of fan-like birefringent structures under cross-polarized light. Sterile monoolein gels (Figure ) and S. aureus subculture alone (Figure ) did not display this transformation over the same time interval. A timelapse of the representative sample is provided as supplementary information.