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Siderophore production by using free and immobilized cells of two pseudomonads cultivated in a medium enriched with Fe and/or toxic metals (Cr, Hg, Pb)
Author(s) -
Braud Armelle,
Jézéquel Karine,
Léger MarieAnne,
Lebeau Thierry
Publication year - 2006
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.20937
Subject(s) - siderophore , pseudomonas fluorescens , pyoverdine , bacteria , chemistry , microorganism , pseudomonas , microbiology and biotechnology , bioaugmentation , food science , growth medium , environmental chemistry , nuclear chemistry , biology , genetics
Pseudomonads are serious candidates for siderophore production applied to toxic metal (TM) solubilization. The bioaugmentation of contaminated soils by these TM‐solubilizing bacteria combined with phytoextraction is an emerging clean‐up technology. Unfortunately, siderophore synthesis may be drastically reduced by soluble iron in soils and bacteria can suffer from TM toxicity. In this study, we compared siderophore production by Pseudomonas aeruginosa and Pseudomonas fluorescens by using free and immobilized cells in Ca‐alginate beads incubated in a medium containing Fe and/or TM (mixture of Cr, Hg, and Pb in concentrations which represented the soluble fraction of a contaminated agricultural soil). Free cell growth was stimulated by Fe, whatever the microorganism, the inoculum size and the presence or not of TM might have been. P. aeruginosa was less sensitive to TM than P. fluorescens . By comparison with free cells, immobilization with the high inoculum size showed less sensitivity to TM most probably because of lower metal diffusion in beads. Indeed, a maximum of 99.1% of Cr, 57.4% of Hg, and 99.6% of Pb were adsorbed onto beads. The addition of iron in the culture medium reduced significantly siderophore production of free cells while it led only to a low decrease with their immobilized counterparts, in particular with P. aeruginosa . In culture medium enriched with Fe and/or TM, siderophore‐specific production of immobilized cells was higher than for free cells. © 2006 Wiley Periodicals, Inc.