Bacterial gliding is a process of motility whereby a
bacterium can move under its own power. Generally, the process occurs whereby the bacterium moves along a surface in the general direction of its long axis. Gliding may occur via distinctly different mechanisms, depending on the type of bacterium. This type of movement has been observed in phylogenetically diverse bacteria such as
cyanobacteria,
myxobacteria,
cytophaga,
flavobacteria, and
mycoplasma. The first report of gliding motility in the
Desulfobulbaceae family has been shown in
cable bacteria.
Myxococcus xanthus cells exhibit a coordinated swarming behavior which may be observed macroscopically as a rhythmic rippling. Upon encountering cellular debris or other macromolecules, aligned
M. xanthus cells will form converging or diverging "accordion waves". As converging waves meet, cell reversals occur and the waves reflect away from each other. Bacteria move in response to varying climates, water content, presence of other organisms, and firmness of surfaces or media. Gliding has been observed in a wide variety of phyla, and though the mechanisms may vary between bacteria, it is currently understood that it takes place in environments with common characteristics, such as firmness and low-water, which enables the bacterium to still have motility in its surroundings. Such environments with low-water content include
biofilms,
soil or
soil crumbs in
tilth, and
microbial mats. b)
Specific motility membrane proteins:
Transmembrane proteins are attached to the host surface. This adhesion complex can either be specific to a certain type of surface like a certain cell type or generic for any solid surface. Motor proteins attached to an inner membrane force the movement of the internal cell structures in relation to the transmembrane proteins creating net movement. This is driven by the proton motive force. The proteins involved differ between species. An example of a bacterium that uses this mechanism would be
Flavobacterium. This mechanism is still being studied and is not well understood. c)
Polysaccharide jet: The cell releases a 'jet' of
polysaccharide material behind it propelling it forward. This polysaccharide material is left behind. Cell-invasion and gliding motility have TRAP (
thrombospondin-related anonymous protein), a surface protein, as a common molecular basis that is both essential for infection and locomotion of the invasive apicomplexan parasite.
Micronemes are secretory organelles on the apical surface of the apicomplexans used for gliding motility.
Other proposed mechanisms The mechanism of gliding might differ between species. Examples of such mechanisms include: •
Motor proteins found within the inner membrane of the bacteria utilize a proton-conducting channel to transduce a mechanical force to the cell surface. Motor and regulatory proteins that convert intracellular motion into mechanical forces like traction force have been discovered to be a conserved class of intracellular motors in bacteria that have been adapted to produce cell motility. as a proposed type of gliding motility, involving transient adhesion complexes fixed to the substrate while the organism moves forward. a social bacterium. • Ejection or secretion of a
polysaccharide slime from nozzles at either end of the cell body. • Energized nano-machinery or large macromolecular assemblies located on the bacterium's cell body.
Flavobacterium johnsoniae move via a screw-like mechanism and are powered by a proton motive force.
Swarming motility occurs on softer semi-solid and solid surfaces (which usually involves movement of a bacterial population in a coordinated fashion via
quorum sensing, using flagella to propel them), or
twitching motility Purpose Gliding, as a form of motility, appears to allow for interactions between bacteria,
pathogenesis, and increased social behaviours. It may play an important role in
biofilm formation, bacterial
virulence, and
chemosensing. ==See also==