Effects and mechanisms of modified biochars on microbial iron reduction of Geobacter sulfurreducens

ABSTRACT Microbial iron reduction is considered to be a significant subsurface process. The rate-limiting bioavailability of the insoluble iron oxyhydroxides, however, is a topic for debate. Surface area and mineral structure are recognized as crucial parameters for microbial reduction rates of bulk, macroaggregate iron minerals. However, a significant fraction of iron oxide minerals in the subsurface is supposed to be present as nanosized colloids. We therefore studied the role of colloidal iron oxides in microbial iron reduction. In batch growth experiments with Geobacter sulfurreducens, colloids of ferrihydrite (hydrodynamic diameter, 336 nm), hematite (123 nm), goethite (157 nm), and akaganeite (64 nm) were added as electron acceptors. The colloidal iron oxides were reduced up to 2 orders of magnitude more rapidly (up to 1,255 pmol h− 1 cell− 1) than bulk macroaggregates of the same iron phases (6 to 70 pmol h− 1 cell− 1). The increased reactivity was not only due to the large surface areas of the colloidal aggregates but also was due to a higher reactivity per unit surface. We hypothesize that this can be attributed to the high bioavailability of the nanosized aggregates and their colloidal suspension. Furthermore, a strong enhancement of reduction rates of bulk ferrihydrite was observed when nanosized ferrihydrite aggregates were added.

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THE ACID-BASE PROPERTIES OF CLAY MINERALS AS A POTENTIAL BUFFER FOR SEDIMENT PORE WATER PH AND CARBONATE SATURATION DURING MICROBIAL IRON REDUCTION

10.1130/abs/2018am-324490 ◽

2018 ◽

Author(s):

N. Tanner Mills ◽

◽

Julia S. Reece ◽

Michael M. Tice

Keyword(s):

Clay Minerals ◽

Pore Water ◽

Iron Reduction ◽

Acid Base ◽

Sediment Pore Water ◽

Microbial Iron Reduction ◽

Water Ph ◽

Base Properties

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Predominant microbial iron reduction in sediment in early Cambrian sulfidic oceans

Global and Planetary Change ◽

10.1016/j.gloplacha.2021.103637 ◽

2021 ◽

pp. 103637

Author(s):

Chaochao Xing ◽

Xianguo Lang ◽

Haoran Ma ◽

Yang Peng ◽

Yongbo Peng ◽

...

Keyword(s):

Iron Reduction ◽

Early Cambrian ◽

Microbial Iron Reduction

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Unexpected Genomic Features of High Current Density-Producing Geobacter sulfurreducens strain YM18

FEMS Microbiology Letters ◽

10.1093/femsle/fnab119 ◽

2021 ◽

Author(s):

Takashi Fujikawa ◽

Yoshitoshi Ogura ◽

Koki Ishigami ◽

Yoshihiro Kawano ◽

Miyuki Nagamine ◽

...

Keyword(s):

Electron Transfer ◽

Current Density ◽

Iron Reduction ◽

High Current Density ◽

Model Organism ◽

Geobacter Sulfurreducens ◽

Extracellular Electron Transfer ◽

High Current ◽

Current Production ◽

Current Densities

Abstract Geobacter sulfurreducens produces high current densities and it has been used as a model organism for extracellular electron transfer studies. Nine G. sulfurreducens strains were isolated from biofilms formed on an anode poised at –0.2 V (vs. SHE) in a bioelectrochemical system in which river sediment was used as an inoculum. The maximum current density of an isolate, strain YM18 (9.29 A/m2), was higher than that of the strains PCA (5.72 A/m2), the type strain of G. sulfurreducens, and comparable to strain KN400 (8.38 A/m2), which is another high current producing strain of G. sulfurreducens. Genomic comparison of strains PCA, KN400, and YM18 revealed that omcB, xapD, spc, and ompJ, which are known to be important genes for iron reduction and current production in PCA, were not present in YM18. In the PCA and KN400 genomes, two and one region (s) encoding CRISPR/Cas systems were identified, respectively, but they were missing in the YM18 genome. These results indicate that there is genetic variation in the key components involved in extracellular electron transfer among G. sulfurreducens strains.

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