11 research outputs found
Reduced adhesion between cells and substrate confers selective advantage in bacterial colonies
Microbial colonies cultured on agar Petri dishes have become a model system
to study biological evolution in populations expanding in space. Processes such
as clonal segregation and gene surfing have been shown to be affected by
interactions between microbial cells and their environment. In this work we
investigate the role of mechanical interactions such as cell-surface adhesion.
We compare two strains of the bacterium E. coli: a wild-type strain and a
"shaved" strain that adheres less to agar. We show that the shaved strain has a
selective advantage over the wild type: although both strains grow with the
same rate in liquid media, the shaved strain produces colonies that expand
faster on agar. This allows the shaved strain outgrow the wild type when both
strains compete for space. We hypothesise that, in contrast to a more common
scenario in which selective advantage results from increased growth rate, the
higher fitness of the shaved strain is caused by reduced adhesion and friction
with the agar surface.Comment: 7 pages, 7 figures, submitted to the EPL Special Issue "Evolutionary
modeling and experimental evolution
Bacterial growth: a statistical physicist's guide
Bacterial growth presents many beautiful phenomena that pose new theoretical
challenges to statistical physicists, and are also amenable to laboratory
experimentation. This review provides some of the essential biological
background, discusses recent applications of statistical physics in this field,
and highlights the potential for future research
Extracellular matrix of the central nervous system: from neglect to challenge
The basic concept, that specialized extracellular matrices rich in hyaluronan, chondroitin sulfate proteoglycans (aggrecan, versican, neurocan, brevican, phosphacan), link proteins and tenascins (Tn-R, Tn-C) can regulate cellular migration and axonal growth and thus, actively participate in the development and maturation of the nervous system, has in recent years gained rapidly expanding experimental support. The swift assembly and remodeling of these matrices have been associated with axonal guidance functions in the periphery and with the structural stabilization of myelinated fiber tracts and synaptic contacts in the maturating central nervous system. Particular interest has been focused on the putative role of chondroitin sulfate proteoglycans in suppressing central nervous system regeneration after lesions. The axon growth inhibitory properties of several of these chondroitin sulfate proteoglycans in vitro, and the partial recovery of structural plasticity in lesioned animals treated with chondroitin sulfate degrading enzymes in vivo have significantly contributed to the increased awareness of this long time neglected structure