Biology subjects

van Teeffelen, S.

Publications and source records attributed to van Teeffelen, S..

3 recordsLinked to original sources

bioRxiv2018

Cell Diameter in Bacillus subtilis is Determined by the Opposing Actions of Two Distinct Cell Wall Synthetic Systems

Rod shaped bacteria grow by adding material into their cell wall via the action of two spatially distinct enzymatic systems: The Rod system moves around the cell circumference, while the class A penicillin-binding proteins (aPBPs) are unorganized. To understand how the combined action of these two systems defines bacterial dimensions, we examined how each system affects the growth and width of Bacillus subtilis, as well as the mechanical anisotropy and orientation of material within their sacculi. We find that rod diameter is not determined by MreB, rather it depends on the balance between the systems: The Rod system reduces diameter, while aPBPs increase it. RodA/PBP2A can both thin or widen cells, depending on its levels relative to MreBCD. Increased Rod system activity correlates with an increased density of directional MreB filaments, and a greater fraction of directionally moving PBP2A molecules. This increased circumferential synthesis increases the amount of oriented material within the sacculi, increasing their mechanical anisotropy and reinforcing rod shape. Together, these experiments explain how the combined action of the two main cell wall synthetic systems build rods of different widths, a model that appears generalizable: Escherichia coli containing Rod system mutants show the same relationship between the density of directionally moving MreB filaments and cell width.

microbiology↗

bioRxiv2018

A matrix protein acts as a cue to preserve collective motility of B. subtilis biofilm cells

Bacteria in nature are usually found in complex multicellular communities, termed biofilms. Biofilms are generally seen as sessile structures, resulting from downregulation of motility. However, during interspecies competition and predation, biofilm cells were shown to migrate towards competitor colonies. Here, we show that a specific extracellular matrix (ECM) protein, TasA, is essential for collective migration toward potential competitors and serves as a developmental cue that increases the formation of motile offspring from sessile chains. We reveal an effective strategy to maintain migration capacities in bacterial biofilms: besides providing a three-dimensional adhesive scaffold for the cells, TasA acts as a signal within the bacterial community.

microbiology↗

bioRxiv2017

Engineered CRISPR-Cas9 system enables noiseless, fine-tuned and multiplexed repression of bacterial genes

Over the past few years, tools that make use of the Cas9 nuclease have led to many breakthroughs, including in the control of gene expression. The catalytically dead variant of Cas9 known as dCas9 can be guided by small RNAs to block transcription of target genes, in a strategy also known as CRISPRi. Here, we reveal that the level of complementarity between the guide RNA and the target controls the rate at which dCas9 successfully blocks the RNA polymerase. We use this mechanism to precisely and robustly reduce gene expression by defined relative amounts. We demonstrate broad applicability of this method to the study of genetic regulation and cellular physiology. First, we characterize feedback strength of a model auto-repressor. Second, we study the impact of copy-number variations of cell-wall synthesizing enzymes on cell morphology. Finally, we demonstrate that this system can be multiplexed to obtain any combination of fractional repression of two genes.

synthetic biology↗