Cell cycle control in C.crescentus, an asymmetric bacterium
Using the polarized bacterium Caulobacter crescentus as model system, we showed that the TipN polarity determinant, a membrane-anchored coiled coil protein, is inserted at the newborn pole as soon as it is manufactured (at cell division) to then recruit flagellum assembly factors at the pole predetermined for flagellation.
We also elucidated a mechanism of cell polarization specific for the old pole that carries a stalk and subsequently unraveled a new cell bi-polarization pathway, including a determinant for the assembly of polar pili. We fortuitously discovered that induction of an RND-type efflux pump by the quinolone antibiotic nalidixic acid, Nal, is more deleterious to cells lacking TipN compared to WT cells, rather than beneficial as typically seen.
We then found that the induction by Nal can be attenuated by activation of an RNAse toxin component of toxin-antitoxin system, providing a compelling example of how a toxin can protect against the lethal action of Nal by cleaving the mRNA encoding the RND pump. Recent, chemical-genetics experiments revealed that the pump can also expel certain beta-lactam antibiotics and thus confer resistance independently of the metallo-beta-lactamase that confers resistance to beta-lactams in C. crescentus and its relatives.
Specific expertise
- Genetics, ChIP-Seq, TN-Seq, glycobiology, fluorescence microscopy, antibiotic resistance
Selected Publications
Ardissone, S., N. Kint and P. H. Viollier (2020) Specificity in glycosylation of multiple flagellins by the modular and cell cycle regulated glycosyltransferase FlmG. Elife 9:e60488. doi: 10.7554/eLife.60488.
Ardissone, S. N. Kint, B. Petrignani, G. Panis and P. H. Viollier (2020) Secretion relieves translational co-repression by a specialized flagellin paralog. Dev Cell: 55(4):500-513.e4. doi: 10.1016/j.devcel.2020.10.005.
Kirkpatrick, C.L., D. Martins, P. Redder, A. Frandi, J. Mignolet, J. Bortoli Chapalay, M. Chambon and P.H. Viollier (2016). Growth control switch by a DNA damage-inducible toxin-antitoxin system in Caulobacter crescentus. Nature Microbiology, doi:10.1038/nmicrobiol.2016.8
Joshi, K., M. Bergé, M., S. K. Radhakrishnan, P.H. Viollier and P. Chien (2015). An adaptor hierarchy regulates proteolysis during a bacterial cell cycle. Cell, 163(2):419-31. doi: 10.1016/j.cell.2015.09.030
Huitema, E., D. Matteson, S. Pritchard, S. Kumar Radhakrishnan and P.H. Viollier (2006) Bacterial birth scar proteins mark future flagellum assembly site. Cell 124(5):1025-37
6 Nov 2020