Spectrophotometric ferric ion biosensor from Pseudomonas fluorescens culture

Abstract

Pseudomonas fluorescens cultures produce fluorescent siderophores. By utilizing optimal conditions for maximizing siderophore production in shake flask cultures of P. fluorescens, we report successful characterization of the culture broth supernatant as a robust ferric ions biosensor. For characterizing the ferric ions biosensor, we tested the effects of pH, buffers, different ferric salts and possible interference by ferrous ions under different solution conditions. We find that the biosensor is very specific to ferric ions only with sensitivity to concentrations as low as 10 microM. Further, the response time of the biosensor is the shortest (approximately 5 min or smaller) for citrate as the accompanying anion with ferric ions. While the response time is longer than that expected of normal biosensors, it is well compensated by the simplicity and economics of the biosensor production. Extremely low standard deviations in several experimental repeats also highlight the robustness of the ferric ions biosensor. Most importantly, the biosensor is extremely easy to use due to its straightforward spectrophotometric applications. We also show the utility of the biosensor with the high resolution technique of fluorescence microscopy. Finally, we report a novel mechanistic finding that siderophores present in the culture broth supernatants have two distinct optically active sites on them, which can be monitored independently in presence or absence of ferric ions.

Microbial siderophores and their potential applications: a review

“…Biosensor is a simple, integrated device capable of generating specific quantitative or semi-quantitative analytical information using a biological recognition element attached to a transducer (Thevenot et al 1999;Gupta et al 2008). A biosensor generally consists of a biorecognition component, biotransducer component, and electronic system containing a signal amplifier, processor, and display (Eggins 1996).…”

“…The concentration of iron present in ocean has been quantified by using a siderophore named as parabactin secreted from Paracoccus denitrificans (Chung Chun Lam et al 2006). Siderophores present in crude culture broth supernatant of Pseudomonas fluorescens have been characterized to function as a sensitive, robust, and specific Fe 3+ biosensor (Gupta et al 2008). This siderophore-based biosensor is cheap, userfriendly, and simple as it relies only on spectrophotometer (Gupta et al 2008).…”

“…Siderophores present in crude culture broth supernatant of Pseudomonas fluorescens have been characterized to function as a sensitive, robust, and specific Fe 3+ biosensor (Gupta et al 2008). This siderophore-based biosensor is cheap, userfriendly, and simple as it relies only on spectrophotometer (Gupta et al 2008). Another study suggested the use of the fluorescent siderophore derivative MA-DFB to act as a photoactive sensor for the biologically available iron content in aquatic systems (Orcutt et al 2010).…”

Biosensor: an emerging safety tool for meat industry

“…Biosensor based on optical transduction can detect the inhibition of the enzyme urease and can sense down to 100 ppm of cadmium (Verma et al 2010). Among the optical biosensors the following have been reported: devices using fluorescence microscopy and fluorescence quenching applied to siderophore bacteria biomediators (Adam et al 2005) or using FRET and SPR applied to chelating fluorescent protein biomediators and albumin-based biosensors (Chung et al 2006;Gupta et al 2008).…”

Iron specificity of a biosensor based on fluorescent pyoverdin immobilized in sol-gel glass

“…These include: iron sensors based on 1,10-phenanthroline entrapped in sol-gel glass [2,3] ; various fluorescent probes used to detect iron in biological systems [4] ; and ferric ion biosensors using fluorescent siderophores such as azotobactin δ [5], parabactin [6], and pyoverdin [7-10] .…”