Abstract
Fluorescence emission of pyoverdine – the siderophore synthesized by iron scavenger bacteria - was studied using in vitro cultures of Pseudomonas aeruginosa with the aim to design a biosensor system for liquid sample iron loading. Diluted suspensions of colloidal magnetite nanoparticles were supplied in the culture medium (10 microl/l and 100 microl/l) to simulate magnetic loading with iron oxides of either environmental waters or human body fluids. The electromagnetic exposure to radiofrequency waves of bacterial samples grown in the presence of magnetic nanoparticles was also carried out. Cell density diminution but fluorescence stimulation following 10 microl/l ferrofluid addition and simultaneous exposure to radiofrequency waves was evidenced. The inhibitory influence of 100 microl/l ferrofluid combined with RF exposure was evidenced by fluorescence data. Mathematical model was proposed to approach quantitatively the dynamics of cell density and fluorescence emission in relation with the consumption of magnetite nanoparticle supplied medium. The biosensor scheme was shaped based on the response to iron loading of bacterial sample fluorescence.
Highlights
Fluorescence phenomena in the living world were evidenced by using sensitive photo-detectors, able to record slight emissions of visible electromagnetic radiation generated at the level of various cells and tissues: seeds, roots and leaves of most plant species, neurons, liver or skin cells of numerous animals as well as in microorganism cells – fungi and bacteria
Wild strain of Pseudomonas aeruginosa was isolated from hospital patient with digestive diseases; adequate aliquots of 18 hours aged cells were inoculated in sterile glass tubes containing liquid broth culture medium supplemented with magnetic fluid dilutions
The assay of siderophore accumulation was carried out by fluorescence investigation upon the supernatant liquid containing bacterial pyoverdine – released following the culture cell thermolysis (Perkin Elmer spectrofluorimeter, excitation light of 300 nm wavelength; fluorescence quenching being avoided by 1:10 dilution) The experiment was repeated five times, the same bacterial strain being used as iron loading probe
Summary
Fluorescence phenomena in the living world were evidenced by using sensitive photo-detectors, able to record slight emissions of visible electromagnetic radiation generated at the level of various cells and tissues: seeds, roots and leaves of most plant species, neurons, liver or skin cells of numerous animals as well as in microorganism cells – fungi and bacteria. Among fluorescent bacteria there are certain Pseudomonas species characterized by the ability of iron uptake and chelating in the form of pyoverdine – a siderophore with blue greenish fluorescence [1], that can be further internalized by the plant roots for example. Based on Pseudomonas putida Perry et al, [4] reported the design of a sensor system that responded in a rapid time with altered light emission when it was exposed to increasing levels of toxic metal ions: Cu(II), Zn, Pb, and Cd. Based on Pseudomonas putida Perry et al, [4] reported the design of a sensor system that responded in a rapid time with altered light emission when it was exposed to increasing levels of toxic metal ions: Cu(II), Zn, Pb, and Cd Both Pseudomonas fluorescens and Pseudomonas aeruginosa, producing structurally different pyoverdines, have demonstrated highly efficient cross-reactions when tested for pyoverdinemediated iron uptake. In the the authors focused on Pseudomonas aeruginosa since it is characterized by various ecological nishes including human body so that the iron detection could be of environmental and of medical interest
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