title: Population Changes in a Community of Alkaliphilic Iron-Reducing Bacteria Due to Changes in the Electron Acceptor: Implications for Bioremediation at Alkaline Cr(VI)-Contaminated Sites.
abstract: A serial enrichment culture has been grown in an alkaline Fe(III)-citrate-containing medium from an initial inoculum from a soil layer beneath a chromium ore processing residue (COPR) disposal site where Cr(III) is accumulating from Cr(VI) containing leachate. This culture is dominated by two bacterial genera in the order Clostridiales,Tissierella, and an unnamedClostridium XIsubgroup. This paper investigates the growth characteristics of the culture when Cr(VI) is added to the growth medium and when aquifer sand is substituted for Fe(III)-citrate. The aim is to determine how the availability and chemical form of Fe(III) affects the growth of the bacterial consortium, to determine the impact of Cr(VI) on growth, and thus attempt to understand the factors that are controlling Cr(III) accumulation beneath the COPR site. The culture can grow fermentatively at pH 9.2, but growth is stronger when it is associated with Fe(III) reduction. It can withstand Cr(VI) in the medium, but growth only occurs once Cr(VI) is removed from solution. Cr(VI) reduced the abundance ofTissierella sp. in the culture, whereas theClostridium XIsp. was Cr(VI) tolerant. In contrast, growth with solid phase Fe(III)-oxyhydroxides (present as coatings on aquifer sand) favoured theTissierella Csp., possibly because it produces riboflavin as an extracellular electron shuttling compound allowing more efficient electron transfer to solid Fe(III) phases. Thus, it is suggested that bacterially mediated Cr(III) reduction in the soil beneath the COPR site is dependent on Fe(III) reduction to sustain the bacterial community.
authors.affiliation: School of Civil Engineering, University of Leeds, Leeds, LS2 9JT UK.
authors.forename: Samuel J
authors.initials: SJ
authors.lastname: Fuller
authors.affiliation: School of Earth and Environment, University of Leeds, Leeds, LS2 9JT UK.
authors.forename: Ian T
authors.initials: IT
authors.lastname: Burke
authors.affiliation: University Hospital Jena, Friedrich-Schiller University, 07743 Jena, Germany.
authors.forename: Duncan G G
authors.initials: DG
authors.lastname: McMillan
authors.affiliation: School of Process, Environmental and Materials Engineering, University of Leeds, Leeds, LS2 9JT UK.
authors.forename: Weixuan
authors.initials: W
authors.lastname: Ding
authors.affiliation: School of Civil Engineering, University of Leeds, Leeds, LS2 9JT UK.
authors.forename: Douglas I
authors.identifier: 0000-0001-5144-1234
authors.initials: DI
authors.lastname: Stewart
keywords: Alkaliphile; Bacteria; Bioremediation; COPR; Chromium; Iron