title: Contribution of extracellular polymeric substances from Shewanella sp. HRCR-1 biofilms to U(VI) immobilization.
abstract: The goal of this study was to quantify the contribution of extracellular polymeric substances (EPS) to U(VI) immobilization by Shewanella sp. HRCR-1. Through comparison of U(VI) immobilization using cells with bound EPS (bEPS) and cells with minimal EPS, we show that (i) bEPS from Shewanella sp. HRCR-1 biofilms contribute significantly to U(VI) immobilization, especially at low initial U(VI) concentrations, through both sorption and reduction; (ii) bEPS can be considered a functional extension of the cells for U(VI) immobilization and they likely play more important roles at lower initial U(VI) concentrations; and (iii) the U(VI) reduction efficiency is dependent upon the initial U(VI) concentration and decreases at lower concentrations. To quantify the relative contributions of sorption and reduction to U(VI) immobilization by EPS fractions, we isolated loosely associated EPS (laEPS) and bEPS from Shewanella sp. HRCR-1 biofilms grown in a hollow fiber membrane biofilm reactor and tested their reactivity with U(VI). We found that, when reduced, the isolated cell-free EPS fractions could reduce U(VI). Polysaccharides in the EPS likely contributed to U(VI) sorption and dominated the reactivity of laEPS, while redox active components (e.g., outer membrane c-type cytochromes), especially in bEPS, possibly facilitated U(VI) reduction.
authors.affiliation: The Gene and Linda Voiland School of Chemical Engineering and Bioengineering and the Center for Environmental, Sediment and Aquatic Research, Washington State University, Pullman, Washington, United States.
authors.forename: Bin
authors.initials: B
authors.lastname: Cao
authors.forename: Bulbul
authors.initials: B
authors.lastname: Ahmed
authors.forename: David W
authors.initials: DW
authors.lastname: Kennedy
authors.forename: Zheming
authors.initials: Z
authors.lastname: Wang
authors.forename: Liang
authors.initials: L
authors.lastname: Shi
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Marshall
authors.forename: Jim K
authors.initials: JK
authors.lastname: Fredrickson
authors.forename: Nancy G
authors.initials: NG
authors.lastname: Isern
authors.forename: Paul D
authors.initials: PD
authors.lastname: Majors
authors.forename: Haluk
authors.initials: H
authors.lastname: Beyenal
mesh_terms: D018441:Biofilms; D005110:Extracellular Space / Q000737:chemistry*; D046911:Macromolecular Substances / Q000032:analysis / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D011134:Polysaccharides / Q000032:analysis / Q000378:metabolism*; D045483:Rivers / Q000382:microbiology; D020592:Shewanella / Q000737:chemistry*; D017974:Uranium Compounds / Q000378:metabolism*; D014861:Washington
chemical_list: D046911:Macromolecular Substances; D011134:Polysaccharides; D017974:Uranium Compounds