HR: 1340h
AN: B53C-1014    [Abstracts]
TI: Manganese and Iron Interactions in Cave and Rock Varnish Communities
AU: Boston, P J
EM: pboston@nmt.edu
AF: New Mexico Tech., 801 Leroy Place, Socorro, NM 87801 United States
AU: Spilde, M N
EM: mspilde@unm.edu
AF: Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131 United States
AU: Northup, D E
EM: dnorthup@unm.edu
AF: Dept. of Biology, University of New Mexico, Albuquerque, NM 87131 United States
AU: * Mullen, K
EM: mkristen@nmt.edu
AF: New Mexico Tech., 801 Leroy Place, Socorro, NM 87801 United States
AU: Bargar, J
EM: bargar@slac.stanford.edu
AF: Stanford Synchrotron Radiation Laboratory, 2575 Sand Hill Rd., Bldg 137, Menlo Park, CA 94025 United States
AU: Carey, R
AF: Institute of Meteoritics, University of New Mexico, Albuquerque, NM 87131 United States
AB: Microbial communities in arid land caves and surface desert environments interact with Fe and Mn, yielding deposits of intimately associated Fe- and Mn-oxides as a result. Although the geological setting and fundamental rock makeup may be similar in some cases, the environments of these two types of communities differ radically. The manner in which the organisms interact with the rock environment may reflect these differences in the resulting minerals, although the biological oxidation mechanisms of Mn and Fe may be similar. We are mapping the Mn and Fe deposition patterns in the mineral coatings in relation to the concentrations of organic carbon indicative of microbial presence, identifying minerals that are biogenic, along with isolating the perpetrators responsible and reproducing relevant minerals in the laboratory. We are also uncovering the underlying biodiversity as revealed by molecular phylogenetic techniques. The ultimate goal is to determine the degree of microbial responsibility for the secondary mineral deposits observed and the potential role of these communities in both dissolution of subsurface bedrock and deposition of surface oxide coatings. Synchrotron XRF and XRD data reveal differences in the mineralogy of the coatings. Lithiophorite is the predominate crystalline Mn-mineral in cave samples, although crystal size is small. TEM analyses show that the Mn-oxides range from amorphous or microcrystalline to exhibiting coherent crystalline lattices. XRF mapping indicates that Ni, Cu, Zn, As and Pb are associated with the Mn-oxides. In the desert surface oxide samples birnessite predominates the crystalline minerals. X-ray maps show a laminated structure with a complex and variable chemistry, including variability in trace elements such as Ni and Pb. ÿÿÿÿÿÿÿ DNA extraction of rock varnish samples, followed by the construction of clone libraries from community DNA, demonstrated the apparent predominance of cyanobacteria in rock varnish communities. The clone library sequences also revealed the presence of actinobacteria, chloroflexi, Alphaproteobacteria, and environmental isolates whose closest relatives were found in Hawaiian volcanic soils, thermal soils, and uranium wastes. Cultured isolates from both environments produce amorphous oxides followed by an array of minerals that undergo increasing crystallization over time (months to years) with live cultures but which cease when cultures are killed.
UR: http://www.i-pi.com/~diana/slime
DE: 0330 Geochemical cycles
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting