title: New insights into the function of a versatile class of membrane molecular motors from studies ofMyxococcus xanthussurface (gliding) motility.
abstract: Cell motility is a central function of living cells, as it empowers colonization of new environmental niches, cooperation, and development of multicellular organisms. This process is achieved by complex yet precise energy-consuming machineries in both eukaryotes and bacteria. Bacteria move on surfaces using extracellular appendages such as flagella and pili but also by a less-understood process called gliding motility. During this process, rod-shaped bacteria move smoothly along their long axis without any visible morphological changes besides occasional bending. For this reason, the molecular mechanism of gliding motility and its origin have long remained a complete mystery. An important breakthrough in the understanding of gliding motility came from single cell and genetic studies in the delta-proteobacteriumMyxococcus xanthus. These early studies revealed, for the first time, the existence of bacterial Focal Adhesion complexes (FA). FAs are formed at the bacterial pole and rapidly move towards the opposite cell pole. Their attachment to the underlying surface is linked to cell propulsion, in a process similar to the rearward translocation of actomyosin complexes in Apicomplexans. The protein machinery that forms at FAs was shown to contain up to seventeen proteins predicted to localize in all layers of the bacterial cell envelope, the cytosolic face, the inner membrane (IM), the periplasmic space and the outer membrane (OM). Among these proteins, a proton-gated channel at the inner membrane was identified as the molecular motor. Thus, thrust generation requires the transduction of traction forces generated at the inner membrane through the cell envelope beyond the rigid barrier of the bacterial peptidoglycan.
authors.affiliation: Laboratoire de Chimie Bactérienne, Institut de Microbiologie de la Méditerranée, CNRS -Aix Marseille University UMR7283, 31 chemin Joseph Aiguier, 13009 Marseille, France.
authors.forename: Tâm
authors.initials: T
authors.lastname: Mignot
authors.affiliation: Centre de Biochimie Structurale, CNRS UMR5048, INSERM U1054, Montpellier University, 29 rue de Navacelles, 34090 Montpellier, France.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Nöllmann
keywords: adhesion; bacterial cell envelope; molecular motors; motility; proton channel