Impact of Organic Carbon Electron Donors on Microbial Community Development under Iron- and Sulfate-Reducing Conditions

• Published in: PloS one 2016-01, Vol.11 (1), p.e0146689-e0146689
• Main Authors: Kwon, Man Jae, O'Loughlin, Edward J, Boyanov, Maxim I, Brulc, Jennifer M, Johnston, Eric R, Kemner, Kenneth M, Antonopoulos, Dionysios A
• Format: Article
• Language: English
• Subjects: Acetic acid; Acetic Acid - metabolism; Anaeromyxobacter; Analysis; Bacteria; Base Sequence; BASIC BIOLOGICAL SCIENCES; Bicarbonate; Bicarbonates; Biodegradation, Environmental; Biogeochemistry; Biology; Biology and Life Sciences; Bottles; Carbon - chemistry; Carbonates; Carbonates - metabolism; Coloration; Community composition; Community development; Desulfotomaculum - genetics; Desulfotomaculum - metabolism; DNA, Bacterial - genetics; DNA, Ribosomal - genetics; Earth Sciences; electron donor; Electrons; Energy Metabolism - physiology; ENVIRONMENTAL SCIENCES; Evolution; Fermentation; Ferric Compounds - metabolism; Ferrous Compounds - metabolism; Genomics; Geochemistry; Glucose; Glucose - metabolism; Groundwater; Inoculum; Iron; Iron oxides; iron reduction; Iron sulfides; Laboratories; Lactic acid; Lactic Acid - metabolism; Metabolic Networks and Pathways - physiology; Metabolism; Microbial activity; microbial community development; Microbial Consortia - physiology; Microbiomes; Microorganisms; Mineralization; Mineralogy; Organic carbon; Oxidation; Oxidation-Reduction; Particle accelerators; Pathways; Phosphates - metabolism; Physical Sciences; Propionic acid; Reduction; RNA, Ribosomal, 16S - genetics; rRNA 16S; sediment; Sediments; Sediments (Geology); Sequence Analysis, DNA; Siderite; Stochasticity; Sulfate reduction; Sulfate-reducing bacteria; Sulfates; Sulfates - metabolism; Sulfide; Sulfides; Sulfur; Vivianite; X ray analysis
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0146689

Although iron- and sulfate-reducing bacteria in subsurface environments have crucial roles in biogeochemical cycling of C, Fe, and S, how specific electron donors impact the compositional structure and activity of native iron- and/or sulfate-reducing communities is largely unknown. To understand this better, we created bicarbonate-buffered batch systems in duplicate with three different electron donors (acetate, lactate, or glucose) paired with ferrihydrite and sulfate as the electron acceptors and inoculated them with subsurface sediment as the microbial inoculum. Sulfate and ferrihydrite reduction occurred simultaneously and were faster with lactate than with acetate. 16S rRNA-based sequence analysis of the communities over time revealed that Desulfotomaculum was the major driver for sulfate reduction coupled with propionate oxidation in lactate-amended incubations. The reduction of sulfate resulted in sulfide production and subsequent abiotic reduction of ferrihydrite. In contrast, glucose promoted faster reduction of ferrihydrite, but without reduction of sulfate. Interestingly, the glucose-amended incubations led to two different biogeochemical trajectories among replicate bottles that resulted in distinct coloration (white and brown). The two outcomes in geochemical evolution might be due to the stochastic evolution of the microbial communities or subtle differences in the initial composition of the fermenting microbial community and its development via the use of different glucose fermentation pathways available within the community. Synchrotron-based x-ray analysis indicated that siderite and amorphous Fe(II) were formed in the replicate bottles with glucose, while ferrous sulfide and vivianite were formed with lactate or acetate. These data sets reveal that use of different C utilization pathways projects significant changes in microbial community composition over time that uniquely impact both the geochemistry and mineralogy of subsurface environments.