Measuring mass transfer processes of octane with the help of an alkSalkB::gfp‐tagged Escherichia coli

Abstract

Diffusion of octane from oily droplets in different microscale settings was measured using Escherichia coli expressing the stable green fluorescent protein (GFP) from the alkB promoter of Pseudomonas oleovorans. GFP fluorescence intensities were determined quantitatively at the single-cell level after 1.0 or 2.5 h incubation and compared with different calibration series using known concentrations of octane. By immobilizing the E. coli sensor cells on the bottom glass plate of a microscope flow chamber, it was possible to monitor the diffusion process for octane in aqueous solution as a function of time and distance from non-aqueous phase droplets of octane alone or oily octane mixtures. When a gas phase was included in the flow chambers, octane transport could be demonstrated from the oily mixtures to the cells through both gas and liquid phase. Assays of non-immobilized sensor cells in microdroplets in the presence or absence of soil particles incubated with octane through the vapour phase revealed a slight reduction in the total amount of induced E. coli cells in the presence of soil. Our results indicate the power of using GFP-marked single-cell biosensors in determining microscale bioavailability of organic pollutants.

Highly variable individual donor cell fates characterize robust horizontal gene transfer of an integrative and conjugative element

“…A 752-bp promoterless egfp gene was amplified from a derivative of plasmid pJAMA23 (47) and inserted 27 bp downstream of the stop codon of intB13 (Fig. S1) in P. putida carrying WT ICEclc (strain 2737) or ICEclc-ΔmfsR [strain 4322 (27)], with the ICE inserted in the gene for tRNA-gly5 (40).…”

Comparison of naphthalene bioavailability determined by whole-cell biosensing and availability determined by extraction with Tenax

“…After 5 min, the glass slides were taken out and rinsed again with demineralized water. Slides were then dried at 44 C for 1 h and used directly for immobilization as described elsewhere (Jaspers et al, 2001). …”

“…EFM images were analyzed by a Metamorph software routine described previously (Kohlmeier et al, 2007;Jaspers et al, 2001;Wells et al, 2005a). In brief, this involves image optimization for counting of fluorescent spots, followed by collection of statistics on each spot (size, shape, factor, average gray value or AGV).…”

Bacterial Transcriptional Regulators for Degradation Pathways of Aromatic Compounds

“…However, regulation of catabolic pathway expression has attracted the interest of numerous different groups, who have tried to unravel the molecular partners in the regulatory process, the signals triggering pathway expression, and the exact mechanisms of activation and repression. More recently, information about regulatory systems has attracted interest, with the potential of these systems being used as sensory mechanisms in whole-cell living bioreporters, genetically modified bacteria which can be used as sensors to measure the quality of aqueous, soil, and air environments (49,96,242). It soon was discovered that a large diversity of regulatory systems existed for mediating the expression of catabolic pathways.…”