Jennie C. Hunter-Cevera

Real-Time Characterization of Biogeochemical Reduction of Cr(VI) on Basalt Surfaces by SR-FTIR Imaging

Synchrotron radiation-based (SR) Fourier-transform infrared (FTIR) spectromicroscopy in the mid-infrared region is a surface analytical technique that can provide direct insights into the localization and real-time mechanisms for the reduction of the (CrO4)2- chromate [Cr(VI)] species on surfaces of geologic materials. Time-resolved SR-FTIR spectra indicate that, in the presence of endoliths (mineral-inhabiting microorganisms), microbial reduction of Cr(VI) to Cr(III) compounds on basaltic mineral surfaces is the key mechanism of Cr(VI) transformation. It proceeds in at least a two-step reaction with Cr(V) compounds as possible intermediate products, with the reduction of Cr(VI) increasing during the concomitant biodegradation of a dilute organic vapor (toluene). Analyses of spatially resolved SR-FTIR spectra show that the maximum reduction of Cr(VI) to Cr(III) compounds occurs on surfaces densely populated by microorganisms. The oxidation state of Cr(III) compounds was confirmed by micro-x-ray absorption...

The value of microbial diversity.

In the past few years, due to the use of molecular methods, our knowledge of microbial diversity has increased dramatically, not only from a phylogenetic and taxonomic perspective but also from an ecological basis. We now know that microorganisms exist in every conceivable place on Earth, even in extreme environments. Temperature may be the only limitation as to where they can and cannot exist and/or function. As more small subunit rDNA sequence information becomes available there is a real need to start turning the information into knowledge that can be applied to better elucidate and understand structure-function relationships within ecosystems, develop new culturing methods, and discover new products and processes. It has been stated on numerous occasions that the 21(st) century is the century for biology. Within that context, we must address the real value of microbial diversity.

Surface-enhanced infrared absorption-reflectance (SEIRA) microspectroscopy for bacteria localization on geologic material surfaces:

Abstract Surface-enhanced infrared absorption-reflectance (SEIRA) microspectroscopy is potentially a useful chemical/biological probe to provide insights into the localization of living endolithic bacteria on the surfaces of geologic materials. This hypothesis was tested by validating and demonstrating the use of SEIRA with a metal-overlayer configuration to identify qualitatively on vesicular basalt surfaces the highly localized differences in the chemical composition and in the structure of clusters of endolithic bacteria, vesicles, and minerals. The metal-overlayer configuration was achieved by evaporating a thin gold-film on basalt specimen surfaces. Fourier-transform SEIRA microspectra of the specimen surfaces were recorded in the 650–4000 cm−1 infrared region at a resolution of 4 cm−1 on a Fourier-transform infrared spectrometer coupled to an infrared microscope. All bacteria-inhabiting surfaces exhibited infrared absorption bands indicative of bacterial cells, bands that became ideal biomarkers by which to detect the presence of bacteria. All basalt surfaces exhibited infrared absorption bands indicative of silicates, bands that became ideal mineral markers by which to detect the presence of silicate-containing minerals and locations of vesicles (gas-bubble cavities). Comparative analysis of space-resolved microspectra suggested that bacteria in the vesicular basalt lived not only on the vesicle surface but that they also penetrated and lived beneath the vesicle surface. The penetration terminated when calcic-plagioclase feldspar became the dominant constituent mineral in the vesicular basalt. With this experimental effort, the practical aspects and the usefulness of SEIRA as a promising tool to complement existing techniques for studying the in-situ localization of living bacteria in geologic materials have been demonstrated.

Detecting exposure to environmental organic toxins in individual cells: towards development of a micro-fabricated device

A new method is being developed for quickly screen for the human exposure potential to polycyclic aromatic hydrocarbons (PAHs) and organochlorines (OCs). The development involves two key elements: identifying suitable signals that represent intracellular changes that are specific to PAH and OC exposure, and constructing a device to guide the biological cell growth so that signals from individual cells are consistent and reproducible. We are completing the identification of suitable signals by using synchrotron radiation-based (SR) Fourier-transform infrared (FTIR) spectromicroscopy in the mid-infrared region (4000 - 400 cm-1). Distinct changes have been observed in the IR spectra after treatment of human cells in culture medium with PAHs and OCs. The potential use of this method for detecting exposure to PAHs and OCs has been tested and compared to a reverse transcription polymerase chain reaction (RT-PCR) assay that quantifies increased expression of the CYP1A1 gene in response to exposure to PAHs or OCs.

Search for ancient microorganisms in Lake Baikal

Lake Baikal in Russia, the worlds oldest and deepest continental lake lies in south central Siberia, near the border to Mongolia. The lake is 1,643 m deep and has an area of about 46,000 km2. It holds one-fifth of all the terrestrial fresh water on Earth. Lake Baikal occupies the deepest portion of the Baikal Rift Zone. It was formed some 30-45 million years ago. The isolated Lake Baikal ecosystem represents a unique niche in nature based on its historical formation. The microbial diversity present in this environment has not yet been fully harvested or examined for products and processes of commercial interest and value. Thus, the collection of water, soil, and sub-bottom sediment samples was decided to characterize the microbial diversity of the isolated strains and to screen the isolates for their biotechnological value.