New Mexico Geological Society Annual Spring Meeting — Abstracts

Multidisciplinary studies that involve geochemists, mineralogists, microbiologists, and molecular biologists can be crucial to our quest to investigate the role that microorganisms play in various geological materials and processes. Biologists have developed a suite of techniques such as DNA stains that reveal cell shapes in rock material, redox dyes that reveal live vs dead cells, and molecular phylogenetic techniques that assist in identifying living organisms present in geological materials using genetic sequences. Functional gene studies also can identify whether genes are present to cany out particular processes such as manganese oxidation.

Our study of the origin of ferromanganese deposits in Lechuguilla and Spider Caves illustrates the effectiveness of multidisciplinary studies. Incubation of deposits with INT (a redox dye) and counter-staining with acridine orange revealed the presence of stalked bacteria (putative manganese-oxidizing bacteria) in the deposits and the underlying punk rock. Analysis of genetic sequences of DNA extracted from the deposits showed only weak evidence for iron- and manganese-oxidizing bacteria. Therefore, enrichment cultures were designed to target these organisms and document their production of iron and manganese oxides. DNA extracted from these enrichments showed the presence of known manganese-oxidizing bacteria. Geological techniques, such as scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and bulk chemistry were used to characterize the mineralogy of the deposits and to search for evidence of bacterial morphologies at every step of the study. Thus, the combination of techniques from the two disciplines more effectively allowed us to tease apart the various aspects of the production of these ferromanganese deposits.