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Brouwers, R.

Publications and source records attributed to Brouwers, R..

2 recordsLinked to original sources

Light-activated signaling in DNA-encoded sender-receiver architectures

Collective decision making by living cells is facilitated by exchange of diffusible signals where sender cells release a chemical signal that is interpreted by receiver cells. Biologists have started to unravel the underlying physicochemical determinants that control the effective communication distance using genetically modified cells. However, living systems are inherently challenging to manipulate and study systematically and quantitatively. Therefore, the development of generic and tunable abiotic mimics featuring compartmentalized signaling is highly desirable. Here, by adapting a previously reported artificial cell-cell communication system, we engineer DNA-encoded sender-receiver architectures, where protein-polymer microcapsules act as cell mimics and molecular communication occurs through diffusive DNA signals. We prepare spatial distributions of sender and receiver protocells using a microfluidic trapping array, and setup a signaling gradient from a single sender cell using light, which activates surrounding receivers through DNA strand displacement. Our systematic analysis reveals how the effective signal range of a single sender is determined by various factors including the density and permeability of receivers, extracellular signal degradation, signal consumption and catalytic regeneration. In addition, we construct a three-population configuration where two sender cells are embedded in a dense array of receivers that implement Boolean logic and investigate spatial integration of non-identical input cues. The results advance our understanding of diffusion-based sender-receiver topologies and present a strategy for constructing spatially controlled chemical communication systems that have the potential to reconstitute collective cellular behavior.Competing Interest StatementThe authors have declared no competing interest.View Full Text

synthetic biology

Stability of β-lactam antibiotics in bacterial growth media

Laboratory assays such as MIC tests assume that antibiotic molecules are stable in the chosen growth medium - but rapid degradation has been observed for antibiotics including {beta}-lactams under some conditions in aqueous solution. Degradation rates in bacterial growth medium are less well known. Here, we develop a delay time bioassay that provides a simple way to estimate antibiotic stability in bacterial growth media. We use the bioassay to measure degradation half-lives of the {beta}-lactam antibiotics mecillinam, aztreonam and cefotaxime in widely-used bacterial growth media based on MOPS and Luria-Bertani (LB) broth. We find that mecillinam degradation can occur rapidly, with a half-life as short as 2 hours in MOPS medium at 37{degrees}C and pH 7.4, and 4-5 hours in LB, but that adjusting the pH and temperature can increase its stability to a half-life around 6 hours without excessively perturbing growth. Aztreonam and cefotaxime were found to have half-lives longer than 6 hours in MOPS medium at 37{degrees}C and pH 7.4, but still shorter than the timescale of a typical minimum inhibitory concentration (MIC) assay. Taken together, our results suggest that care is needed in interpreting MIC tests and other laboratory growth assays for {beta}-lactam antibiotics, since there may be significant degradation of the antibiotic during the assay.

pharmacology and toxicology