HR: 0830h
AN: B21C-0733    [PDF]
TI: FTIR Spectroscopic Study of Mn(II) Oxidizing {\it Pseudomonas putida} GB1 Biofilms on ZnSe, Ge, and CdTe Crystal Surfaces
AU: * Parikh, S J
EM: sjparikh@ag.arizona.edu
AF: Department of Soil, Water, and Environmental Science, The University of Arizona, 429 Shantz Building, Tucson, AZ 85721
AU: Gilbert, H L
EM: hanna@hwr.arizona.edu
AF: Department of Hydrology and Water Resources, The University of Arizona, Harshbarger Building, 1133 E. North Campus Dr., Tucson, AZ 85721
AU: Conklin, M H
EM: mconklin@ucmerced.edu
AF: Division of Engineering, University of California, Merced, PO Box 2039, Merced, CA 94344
AU: Chorover, J
EM: chorover@cals.arizona.edu
AF: Department of Soil, Water, and Environmental Science, The University of Arizona, 429 Shantz Building, Tucson, AZ 85721
AB: {\it Pseudomonas putida} strain GB1 is an aerobic, gram-negative bacterium capable of gaining energy from the biological oxidation of Mn(II). The increased kinetics of Mn(II) oxidation resulting from this microbial catalysis is known to contribute to the formation of Mn(IV) oxides in natural waters. Environmental conditions, including aqueous and surface chemistry, greatly affect the macromolecular composition and surface adhesion behavior of bacteria. For example, the chemistry of GB1 biofilms forming on crystal surfaces is expected to vary with Mn(II) concentration in solution. We used Fourier transform infrared (FTIR) spectroscopy to probe the formation of GB1 biofilms on the surfaces of negatively-charged IR transparent ZnSe, Ge, and CdTe crystal windows. Bacterial adhesion experiments were carried out both in the presence and absence of Mn(II)(aq) with FTIR windows suspended in a bioreactor comprising GB1 cells in a mineral growth medium at pH 7.6 and 30$\deg$C. After 85 h, windows were removed from the reactor and IR spectra were collected. Oxidation of Mn(II) was confirmed via leucoberbelin blue (LBB) indicator and the appearance of Mn-O stretches in biofilm IR spectra. Transmission FTIR spectra do not reveal detectable effects of crystal type on biofilm composition, but do indicate changes in chemistry resulting from introduction of Mn(II). In the presence of Mn(II), spectra of biofilms show higher relative intensity in the carbohydrate region (specifically 1160, 1052 cm$^{-1}$). A down frequency shift in the P=O absorbance was also observed (1240 to 1222 cm$^{-1}$). These results indicate a modification of bacterial cell/biofilm composition resulting during biological oxidation of Mn(II). The CdTe transmission window permits measurements to low wavenumbers ($<$600 cm$^{-1}$) and a peak at 588 cm$^{-1}$ was observed when bacteria were surface-adhered in the presence of Mn(II). This peak, which has been attributed to Mn-O stretching vibrations, may provide an index of Mn oxide crystal growth. Scanning electron microscopy (SEM) images of the transmission crystal surfaces show similar bacterial coverage for each treatment. Transmission electron microscopy (TEM) of the bioreactor suspension revealed needle-like clusters of Mn oxide crystals in association with GB1 biomass and extracellular materials.
DE: 0330 Geochemical cycles
DE: 0400 Biogeosciences
SC: Biogeosciences [B]
MN: 2003 Fall Meeting