Accession Number:

ADA499114

Title:

Microbial Reduction of Structural Fe3+ in Nontronite by a Thermophilic Bacterium and its Role in Promoting the Smectite to Illite Reaction

Descriptive Note:

Journal article

Corporate Author:

NAVAL RESEARCH LAB STENNIS SPACE CENTER MS SEAFLOOR SCIENCES DIRECTORATE

Report Date:

2007-01-01

Pagination or Media Count:

10.0

Abstract:

The illitization process of Fe-rich smectite nontronite NAu-2 promoted by microbial reduction of structural Fe1 was investigated by using a thermophilic metal-reducing bacterium, Thermoanaerobacter ethanolicus, isolated from the deep subsurface. T. ethanolicus was incubated with lactate as the sole electron donor and structural Fe1 in nontronite as the sole electron acceptor, and anthraquinone-2, 6- disulfonate AQDS as an electron shuttle in a growth medium pH 6.2 and 9.2, 65 deg C with or without an external supply of Al and K sources. With an external supply of Al and K. the extent of reduction of Fe-1 in NAu-2 was 43.7 and 40.4 at pH 6.2 and 9.2, respectively. X-ray diffraction and scanning and transmission electron microscopy revealed formation of discrete illite at pH 9.2 with external Al and K sources, while mixed layers of illitesmectite or highly charged smectite were detected under other conditions. The morphology of biogenic illite evolved from lath and flake to pseudo-hexagonal shape. An external supply of Al and K under alkaline conditions enhances the smectite-illite reaction during microbial Fe1 reduction of smectite. Biogenic Si02 was observed as a result of bioreduction under all conditions. The microbially promoted smectite-illite reaction proceeds via dissolution of smectite and precipitation of illite. Thermophilic iron reducing bacteria have a significant role in promoting the smectite to illite reaction under conditions common in sedimentary basins.

Subject Categories:

  • Microbiology
  • Physical Chemistry

Distribution Statement:

APPROVED FOR PUBLIC RELEASE