STRESS BEARING: The intermediate filament-like protein FilP spontaneously assembles into a honeycomb-like network in vitro (1), which explains how it supports newly synthesized sections of cell wall in bacteria that grow by extending from the tip and initiating new branches. In Streptomyces coelicolor, FilP (red) accumulates most densely behind the zone occupied by DivIVA proteins (green), the major component of the polarisome, which orchestrates polar growth (2). The same pattern is observed in new branches (3). The findings suggest that DivIVA recruits FilP to the hypha tip to provide a stress-bearing structure where the nascent cell wall is vulnerable. © LAURIE O'KEEFE
The paper
K. Fuchino et al., “Dynamic gradients of an intermediate filament-like cytoskeleton are recruited by a polarity landmark during apical growth,” PNAS, 110:1889-97, 2013.
Although most bacteria proliferate by dividing across the middle, some species grow by extending from the tip and initiating new branches, called hyphae, in the same way as do filamentous fungi, such as mold. This polar mode of growth involves the insertion of new sections of cell wall, leaving growing tips temporarily weak as new segments are gradually strengthened. Previous studies have revealed the molecular mechanisms orchestrating tip extension, but little was known about how the cells compensate for the resulting vulnerability.
In 2008, Nora Ausmees of Lund University in Sweden and colleagues showed that a filamentous protein called FilP ...
