Spatial Distribution of Geobacteraceae and Sulfate‐Reducing Bacteria During In Situ Bioremediation of Uranium‐Contaminated Groundwater. Issue 2 (22nd March 2013)

• Record Type: Journal Article
• Authors: Dar, Shabir A.; Tan, Hui; Peacock, Aaron D.; Jaffe, Peter; N'Guessan, Lucie; Williams, Kenneth H.; Strycharz‐Glaven, Sarah
• Is Part Of: Remediation. Volume 23:Issue 2(2013)
• Page Start: 31
• Page End: 49
• Publication Date: 2013-03-22
• Subjects: Sanitary engineering -- Periodicals; 628
• DOI: 10.1002/rem.21347
• Languages: English
• ISSNs: 1051-5658

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>Analysis of the physiological status of subsurface microbial communities generally relies on the study of unattached microorganisms in the groundwater. These approaches have been employed in studies on bioremediation of uranium‐contaminated groundwater at a study site in Rifle, Colorado, in which <italic>Geobacter</italic> species typically account for over 90 percent of the microbial community in the groundwater during active uranium reduction. However, to develop efficient <italic>in situ</italic> bioremediation strategies it is necessary to know the status of sediment‐associated microorganisms as well. In order to evaluate the distribution of the natural community of <italic>Geobacter</italic> during bioremediation of uranium, subsurface sediments were packed into either passive flux meters (PFMs) or sediment columns deployed in groundwater monitoring wells prior to acetate injection during <italic>in situ</italic> biostimulation field trials. The trials were performed at the Department of Energy's (DOE's) Rifle Integrated Field Research Challenge site. Sediment samples were removed either during the peak of Fe(III) reduction or the peak of sulfate reduction over the course of two separate field experiments and preserved for microscopy. Direct cell counts using fluorescence <italic>in situ</italic> hybridization (FISH) probes targeting <italic>Geobacter</italic> species indicated that the majority of <italic>Geobacter</italic> cells were unattached during Fe(III) reduction, which typically tracks with elevated rates of uranium reduction. Similar measurements conducted during the sulfate‐reducing phase revealed the majority of <italic>Geobacter</italic> to be attached following exhaustion of more readily bioavailable forms of iron minerals. Laboratory sediment column studies confirmed observations made with sediment samples collected during field trials and indicated that during Fe(III) reduction, <italic>Geobacter</italic> species are primarily unattached (90 percent), whereas the majority of sulfate‐reducing bacteria and <italic>Geobacter</italic> species are attached to sediment surfaces when sulfate reduction is the predominant form of metabolism (75 percent and 77 percent, respectively). In addition, artificial sediment experiments showed that pure cultures of <italic>Geobacter uraniireducens</italic>, isolated from the Rifle site, were primarily unattached once Fe(III) became scarce. These results demonstrate that, although <italic>Geobacter</italic> species must directly contact Fe(III) oxides in order to reduce them, cells do not firmly attach to the sediments, which is likely an adaptive response to sparsely and heterogeneously dispersed Fe(III) minerals in the subsurface. © 2013 Wiley Periodicals, Inc.</p> </abstract>