We study how bacteria build and maintain a healthy cell envelope and resist killing by antibiotics
We employ bacterial genetics, biochemistry and cell biology to study cell envelope remodeling in bacterial pathogens. In particular, we are interested in defining regulatory pathways and functional networks of enzymes involved in cell wall degradation, modification and synthesis as well as factors required for upholding outer membrane barrier function. We seek to understand these processes to gain insight into the mechanistic underpinnings of cell growth and cell shape maintenance as well as to elucidate the mechanism(s) of action of envelope-acting antibiotics.
We are currently focusing on four main aspects of cell wall biology
- Regulation of cell wall hydrolases
Cell wall hydrolases (‘autolysins’) are enzymes that have the potential to degrade the bacterial cell wall. Their activity becomes apparent when cell wall synthesis is halted, e.g. by exposure to an antibiotic; under these conditions bacteria typically lyse and die due to autolysin-mediated cell wall degradation. Under physiological conditions, autolysins are often ‘sculptor/spacemaker’ enzymes that cut the cell wall to permit cell envelope extension and the insertion of large protein complexes or to generate different cell shapes. Given the lethal consequences of dysregulated autolysin activity, these degradation processes must be carefully controlled; however, for most autolysins, the mechanistic details of regulation are unknown. We interrogate the pathways that regulate autolysin activity using bacterial genetics and biochemistry to gain insight into mechanisms of bacterial growth and cell shape maintenance and to uncover novel strategies to enhance the effectiveness of cell wall acting antibiotics.
- Mechanisms of tolerance to beta lactam antibiotics
Many bacterial pathogens are tolerant to the lethal action of the otherwise bactericidal beta lactam antibiotics. Using Vibrio cholerae (the causative agent of cholera disease) as a model organism, we aim to delineate the mechanisms of beta lactam tolerance in this and other pathogens with the goal of devising new strategies to combat bacteria that resist killing by these important antibiotics.
- Cell wall stress sensing
We have recently discovered a histidine kinase/response regulator pair (WigK/R) that mediates tolerance to beta lactam antibiotics in the human pathogen V. cholerae. The WigK/R system is activated after exposure to cell wall damaging antibiotics (e.g. penicillin) and responds by upregulating cell wall synthesis processes, likely in order to counteract the damage caused by exposure to the antibiotic. We are currently investigating the mechanistic details of this damage response.
- Outer membrane permeability barrier
Gram-negative bacteria are intrinsically resistant to a variety of high molecular weight antibiotics due to their outer membrane, which provides a formidable diffusion barrier to such compounds. Using genome wide genetic scans for conditional lethality (TnSeq) we aim to define the factors that are required for upholding this permeability barrier.