Interaction between iron and Pseudomonas aeruginosa biofilms attached to Sepharose surfaces

When Pseudomonas aeruginosa PAO1 biofilms (attached to Sepharose surfaces) were subjected to dissolved Fe3+, Most Fe was removed from solution within 25 h by surface complexation with negatively charged functional groups on t he bacterial cell wall via a nucleation and mineralization process. Chemica l formation of Fe-(hydr)oxides was partially responsible for dissolved Fe r emoval, which stemmed from a pH increase, facilitated by microbial activity . PAO1 used Fe (3+) as an electron acceptor producing Fe2+ under localized anaerobic conditions over the first 50 h. The high ratio of Fe2+ to total F e in solution produced a high proportion of Fe(II) in Fe precipitates; howe ver, as the formation of Fe-(hydr)oxides started after 50 h, the Fe2+ conte nt in solution began to diminish. Biofilms can so influence the local chemi cal conditions and metal speciation that the bulk solution phase is also af fected, thereby mediating a wide-range (bio)geochemical cycling of iron. Lo ng-term survival of natural biofilms, even under strict oligotrophic condit ions, could have a broad lasting effect on the bulk geochemical environment . (C) 2001 Elsevier Science B.V. All rights reserved.