title: Impact of substrates and cell immobilization on siderophore activity by Pseudomonads in a Fe and/or Cr, Hg, Pb containing-medium.
abstract: To increase the amount of bioavailable metals in phytoextraction purposes, soil bioaugmentation with Pseudomonads, as siderophore producers with high metal complexation levels, could be relevant. Unfortunately, siderophore synthesis may be inhibited by soluble iron in soil and bacteria can suffer at the same time from the toxicity of some other metals, predation and oligotrophy. To overcome these drawbacks, we attempted to co-locate a carbon substrate and Pseudomonas aeruginosa or P. fluorescens in Ca-alginate beads. First, free-cell cultures showed that glycerol, fructose, mannitol and skim milk enhanced the siderophore activity which was the highest in the medium with neither Fe or TM (toxic metal) (Cr, Hg and Pb) and the lowest in the Fe-containing medium without TM. The negative effect of iron was partly offset when TM was added to the medium. In a second part, co-location of microorganisms and substrates was only feasible with skim milk. By comparison with free cells, siderophore activity by immobilized cells was higher in culture media containing Fe with or without TM (up to a ratio of 9), and varied in a narrow margin, according to the medium composition.
authors.affiliation: Laboratory GRE (Risk Management and Environment), University of Haute-Alsace, Agency of Colmar, BP 50568, 68 008 Colmar Cedex, France.
authors.forename: Armelle
authors.initials: A
authors.lastname: Braud
authors.forename: Karine
authors.initials: K
authors.lastname: Jézéquel
authors.forename: Thierry
authors.initials: T
authors.lastname: Lebeau
mesh_terms: D000818:Animals; D005632:Fructose / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D005990:Glycerol / Q000494:pharmacology; D007785:Lactose / Q000494:pharmacology; D008353:Mannitol / Q000494:pharmacology; D019216:Metals, Heavy / Q000633:toxicity; D008892:Milk; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D011551:Pseudomonas fluorescens / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D017262:Siderophores / Q000378:metabolism*; D012989:Soil Pollutants / Q000633:toxicity; D013213:Starch / Q000494:pharmacology; D013395:Sucrose / Q000494:pharmacology
chemical_list: D019216:Metals, Heavy; D017262:Siderophores; D012989:Soil Pollutants; D005632:Fructose; D008353:Mannitol; D013395:Sucrose; D013213:Starch; D005947:Glucose; D007785:Lactose; D005990:Glycerol