Kinetics of metal detection by luminescence-based whole-cell biosensors: connecting biosensor response to metal bioavailability, speciation and cell metabolism.

Luminescent whole-cell metal biosensors are genetically engineered cells used for the detection of metals in aqueous solutions. Herein, we detail the quantitative connections between time-response of luminescent bacterial metal sensors and the bioavailability of free and complexed metal species. To that end, we formulate the biophysicochemical dynamics of metal partitioning at a biosensor/solution interface and integrate the required metabolism contribution to cell response.

Comparative Analysis of Cell Metabolic Activity Sensing by Escherichia coli rrnB P1-lux and Cd Responsive-Lux Biosensors: Time-Resolved Experiments and Mechanistic Modelling.

Whole-cell bacterial sensors are used in medical/environmental applications to detect chemicals, and to assess medium toxicity or stress. Non-specific constitutive biosensors generally serve the latter purpose, whereas chemical detection is performed with biosensors involving a specific chemical-inducible promoter. Herein, we show that functioning principles of specific and non-specific whole-cell biosensors are not exclusive as both can probe modulations of cell metabolic activity under stressing conditions.

Exploiting Catabolite Repression and Stringent Response to Control Delay and Multimodality of Bioluminescence Signal by Metal Whole-Cell Biosensors: Interplay between Metal Bioavailability and Nutritional Medium Conditions.

The time-dependent response of metal-detecting whole-cell luminescent bacterial sensors is impacted by metal speciation/bioavailability in solution. The comprehensive understanding of such connections requires the consideration of the bacterial energy metabolism at stake and the effects of supplied food on cells' capability to convert bioaccumulated metals into light. Accordingly, we investigated the time response (48 h assay) of PzntA- Cd biosensors in media differing with respect to sources of amino acids (tryptone or Lysogeny Broth) and carbon (glucose, xylose and mixtures thereof).

Osmotic stress and vesiculation as key mechanisms controlling bacterial sensitivity and resistance to TiO nanoparticles.

Toxicity mechanisms of metal oxide nanoparticles towards bacteria and underlying roles of membrane composition are still debated. Herein, the response of lipopolysaccharide-truncated Escherichia coli K12 mutants to TiO nanoparticles (TiONPs, exposure in dark) is addressed at the molecular, single cell, and population levels by transcriptomics, fluorescence assays, cell nanomechanics and electrohydrodynamics. We show that outer core-free lipopolysaccharides featuring intact inner core increase cell sensitivity to TiONPs.

[Rapid procedure for the preparation of erythrocytes destined for deformability measurements].

A rapid procedure for red blood cell isolation by centrifugation is proposed, in which 96% of leucocytes are removed. The middle age of the erythrocytes is verified. This procedure applied to erythrocyte rheological studies (by the initial filtration flow rate) confirms the decreased deformability of senescent red blood cells.