Development of a biological test to evaluate the bioavailability of iron in culture media

Abstract

Aims: To develop an easy‐to‐use and pathogen‐free protocol giving reliable information on the bioavailability of iron in a medium. Methods and Results: In aerobic conditions, iron bioavailability is very low, and most of its forms cannot be assimilated by micro‐organisms. Media with similar iron contents can differ considerably in iron bioavailability, something that is not easily achieved using conventional physicochemical methods. The assay developed in the present work is based on a pyoverdin siderophore release by fluorescent Pseudomonas in response to iron stress. Conclusions: The test was applied to a complex medium used for the production of diphtheria toxin (DT). A significant difference between the bioavailable iron level and the total chemical concentrations contributed by the various compounds used to make the medium could thus be detected. This can be explained by the formation of salt complexes trapping the iron, which thus cannot be used directly by the micro‐organism for its metabolism. Significance and Impact of the Study: The assay can easily be applied to any medium designed for the production of iron‐regulated compounds. This is particularly useful when dealing with processes that use pathogenic strains as was shown in the case based on DT production.

Paraburkholderia phytofirmans PsJN-Plants Interaction: From Perception to the Induced Mechanisms

“…Iron is essential for microorganisms due to its intervention in the synthesis of many essential components of the cell (Leclère et al, 2009). The availability of iron in the environment to living microbes is very low due to its poor solubility at neutral pH 7 (Andrews et al, 2003).…”

Opening Study on the Development of a New Biosensor for Metal Toxicity Based on Pseudomonas fluorescens Pyoverdine

“…Siderophores have great therapeutic (e.g., drug delivery), as well as analytical prospects [ 18 ]. However, during the last few years, only a few pyoverdine-based biosensors have been studied and developed, most of which are molecule-based [ 19 , 20 , 21 ], while only one is a whole-cell bioassay [ 22 ]. Furthermore, all of these biosensors were intended for the determination of ferric ion in medical or pharmaceutical applications.…”

Unique Metabolic Reprogramming in Pseudomonas Aeruginosa P4 Facilitates the Unusual Concurrence of P-solubilizing and Biocontrol Traits Under P-limitation

“…The column eluates were monitored using a UV detector at 210 nm and gluconic acid was detected and quanti ed by comparing the retention time and peak areas obtained for pure gluconic acid standard (10 mM) subjected to similar analytical conditions. Total siderophores were quantitated using Chromo-azurol S solution assay of P4 culture supernatants and expressed as EDTA equivalents (Leclère et al 2009). Siderophore pyochelin was detected and quanti ed by HPLC using an isocratic gradient comprising of 70 % Solvent A (H 2 O, 0.1 % tri uoroacetic acid) and 30 % Solvent B (95 % acetonitrile, 0.1 % tri uoroacetic acid) and a ow rate of 1 ml/min at 254 nm (Youard et al 2007).…”