and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing the burden, to Departmentof Defense, Washington Headquarters Services, Directorate for Information . 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be award that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid 0MB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) 11-APR-2003 REPORT TYPEJournal article (refereed) NRL/JA/7430~03-4 DATES COVERED (From -To) TITLE AND SUBTITLE Role of Microbes in the SPONSORING/MONITORING AGENCY NAME{S) AND ADDRESS(ES)OFFICE OF NAVAL RESEARCH 800 NORTH QUINCY STREET ARLINGTON VA 22217-5660 SPONSOR/MONITOR'S ACRONYM(S) ONR SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release,distribution is unlimited Approved for public release, distribution is unlimited SUPPLEMENTARY NOTES Science Vol 303 6 February 2004 ABSTRACTTemperature, pressure, and tinne have been thought to control the smectite-to-lllite (S-1) reaction, an important diagenetic process used for petroleum exploration. We demonstrated that microorganisms can promote the S-1 reaction by dissolving smectite through reduction of structural Fe(lll) at room temperature and 1 atmosphere within 14 days. This reaction typically requires conditions of 300° to 350°C, 100 megapascals, and 4 to 5 months in the absence of micrcbial activity. These results challenge the conventional concept of the S-1 reaction and of reaction kinetic models. SUBJECT TERMS

Shewanella putrefaciens CN32 reduces Fe(III) within two illites which have different properties: the Fithian bulk fraction and the <0.2 µm fraction of Muloorina. The Fithian illite contained 4.6% (w/w) total Fe, 81% of which was Fe(III). It was dominated by illite with some jarosite (∼32% of the total Fe(III)) and goethite (11% of the total Fe(III)). The Muloorina illite was pure and contained 9.2% Fe, 93% of which was Fe(III). Illite suspensions were buffered at pH 7 and were inoculated with CN32 cells with lactate as the electron donor. Select treatments included anthraquinone-2,6-disulfonate (AQDS) as an electron shuttle. Bioproduction of Fe(II) was determined by ferrozine analysis. The unreduced and bioreduced solids were characterized by Mössbauer spectroscopy, X-ray diffraction and transmission electron microscopy. The extent of Fe(III) reduction in the bulk Fithian illite was enhanced by the presence of AQDS (73%) with complete reduction of jarosite and goethite and partial reduction of illite. Mössbauer spectroscopy and chemical extraction determined that 21–25% of illite-associated Fe(III) was bioreduced. The extent of bioreduction was less in the absence of AQDS (63%) and only jarosite was completely reduced with partial reduction of goethite and illite. The XRD and TEM data revealed no significant illite dissolution or biogenic minerals, suggesting that illite was reduced in the solid state and biogenic Fe(II) from jarosite and goethite was either released to aqueous solution or adsorbed onto residual solid surfaces. In contrast, only 1% of the structural Fe(III) in Muloorina illite was bioreduced. The difference in the extent and rate of bioreduction between the two illites was probably due to the difference in layer charge and the total structural Fe content between the Fithian illite (0.56 per formula) and Muloorina illite (0.87). There may be other factors contributing to the observed differences, such as expandability, surface area and the arrangements of Fe in the octahedral sheets. The results of this study have important implications for predicting microbe-induced physical and chemical changes of clay minerals in soils and sediments.