27 research outputs found
Exopolysaccharide-Independent Social Motility of Myxococcus xanthus
Social motility (S motility), the coordinated movement of large cell groups
on agar surfaces, of Myxococcus xanthus requires type IV
pili (TFP) and exopolysaccharides (EPS). Previous models proposed that this
behavior, which only occurred within cell groups, requires cycles of TFP extension
and retraction triggered by the close interaction of TFP with EPS. However,
the curious observation that M. xanthus can perform TFP-dependent
motility at a single-cell level when placed onto polystyrene surfaces in a
highly viscous medium containing 1% methylcellulose indicated that “S
motility” is not limited to group movements. In an apparent further
challenge of the previous findings for S motility, mutants defective in EPS
production were found to perform TFP-dependent motility on polystyrene surface
in methylcellulose-containing medium. By exploring the interactions between
pilin and surface materials, we found that the binding of TFP onto polystyrene
surfaces eliminated the requirement for EPS in EPS- cells and thus
enabled TFP-dependent motility on a single cell level. However, the presence
of a general anchoring surface in a viscous environment could not substitute
for the role of cell surface EPS in group movement. Furthermore, EPS was found
to serve as a self-produced anchoring substrate that can be shed onto surfaces
to enable cells to conduct TFP-dependent motility regardless of surface properties.
These results suggested that in certain environments, such as in methylcellulose
solution, the cells could bypass the need for EPS to anchor their TPF and
conduct single-cell S motility to promote exploratory movement of colonies
over new specific surfaces