Ms YONG Mei Hui Adeline
Research Assistant

Adeline Yong investigates on sortase-assembled pili that are known to be virulence factors found in Gram-positive bacteria, such as Streptococci and Enterococci. These pili are translocated across the membrane, assembled into fibres by a pilus-polymerising sortase on the membrane, and are subsequently attached to the cell wall by the membrane-anchored enzyme Sortase A (SrtA). When pilus assembly goes “off pathway”, the cell must respond to pilus subunits accumulating in the membrane. In response to membrane stress of this kind, many bacteria rely on protein quality control processes that involve proteases and chaperones.  In this study, Adeline describes a critical role for the cross-kingdom conserved, membrane-anchored HtrA (high temperature requirement A) chaperone/protease in monitoring pilus biogenesis in Enterococcus faecalis. It was found that, in the absence of HtrA, “off pathway” pilus biogenesis activates a previously uncharacterized two component signal transduction system, hereafter termed MsmRS for membrane stress & morphology, which governs cell separation and morphology phenotypes.  MsmRS expression is also induced upon daptomycin-mediated membrane stress. This discovery suggests that in the event of certain types of membrane stress, including aberrant pilus biogenesis, a cell separation checkpoint is triggered which we postulate may potentially provide a window for cells to respond to and recover from membrane stress events.  Given the conservation of sortase-assembled pili and HtrA across the Streptococci and Enterococci, Adeline propose that the MsmRS checkpoint may be a conserved mechanism by which many Gram positive pathogens monitor sortase-assembled pilus biogenesis.