Biology subjects

Brouwers, R.

Publications and source records attributed to Brouwers, R..

3 recordsLinked to original sources

bioRxiv2024

Surface versus volume synthesis governs growth-dependent efficacy of a β-lactam antibiotic

The efficacy of {beta}-lactam antibiotics depends strongly on bacterial growth rate. This can lead to poor correlation between in vivo action and in vitro assays, hindering effective prescribing - yet the mechanisms underlying growth-rate dependent {beta}-lactam action remain unclear. Here, we investigate growth-rate dependent action of mecillinam, a {beta}-lactam that targets the elongation-mediating PBP2 peptidoglycan transpeptidase enzyme, on Escherichia coli cells. We show that mecillinam alters the balance between the rates of cell surface area and volume synthesis in a growth-rate dependent manner. Under mecillinam treatment, cell volume increases exponentially at a rate [fi]xed by the growth medium, but the cells ability to produce new surface area is compromised by the antibiotic. On rich medium, this imbalance leads to lysis, but on poor medium, slow-growing cells reach a new balance between surface area and volume synthesis, allowing sustained growth even at concentrations of mecillinam far above the EUCAST MIC value. A mathematical model based on surface area vs volume synthesis can quantitatively explain growth-medium dependent differences in mecillinam killing, as well as rescue from killing when cell morphology is perturbed in a microfluidic device. {beta}-lactam antibiotic action is mechanistically complex, yet our work suggests that simple conceptual principles can help understand the interplay between molecular mechanism and cell physiology, potentially contributing to more effective use of these drugs.

microbiology↗

bioRxiv2020

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↗

bioRxiv2020

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↗