Development of a biological test to evaluate the bioavailability of iron in culture media.
OBJECTIVE
To develop an easy-to-use and pathogen-free protocol giving reliable information on the bioavailability of iron in a medium.


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.


CONCLUSIONS
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.
Leclère
V
V
Laboratoire ProBioGEM EA1026, Polytech'lille, Université des Sciences et Technologies de Lille, Villeneuve d'Ascq Cedex, France. valerie.leclere@univ-lille1.fr
Beaufort
S
S
Dessoy
S
S
Dehottay
P
P
Jacques
P
P
D001682:Biological Availability; D003470:Culture Media / Q000737:chemistry*; D004167:Diphtheria Toxin / Q000032:analysis; D007501:Iron / Q000032:analysis*; D009842:Oligopeptides / Q000378:metabolism*; D011549:Pseudomonas / Q000378:metabolism*; D017262:Siderophores / Q000032:analysis*; D013050:Spectrometry, Fluorescence; D013053:Spectrophotometry
D003470:Culture Media; D004167:Diphtheria Toxin; D009842:Oligopeptides; D017262:Siderophores; C042453:pyoverdin; D007501:Iron