Bongkeun Song

Elucidation of Functional Groups on Gram-Positive and Gram-Negative Bacterial Surfaces Using Infrared Spectroscopy

Surface functional group chemistry of intact Gram-positive and Gram-negative bacterial cells and their isolated cell walls was examined as a function of pH, growth phase, and growth media (for intact cells only) using attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy. Infrared spectra of aqueous model organic molecules, representatives of the common functional groups found in bacterial cell walls (i.e., hydroxyl, carboxyl, phosphoryl, and amide groups), were also examined in order to assist the interpretation of the infrared spectra of bacterial samples. The surface sensitivity of the ATR-FTIR spectroscopic technique was evaluated using diatom cells, which possess a several-nanometers-thick layer of glycoprotein on their silica shells. The ATR-FTIR spectra of bacterial surfaces exhibit carboxyl, amide, phosphate, and carbohydrate related features, and these are identical for both Gram-positive and Gram-negative cells. These results provide direct evidence to the previously held conviction that the negative charge of bacterial surfaces is derived from the deprotonation of both carboxylates and phosphates. Variation in solution pH has only a minor effect on the secondary structure of the cell wall proteins. The cell surface functional group chemistry is altered neither by the growth phase nor by the growth medium of bacteria. This study reveals the universality of the functional group chemistry of bacterial cell surfaces.

Anaerobic ammonium oxidation (anammox) in Chesapeake Bay sediments.

Anaerobic ammonium oxidation (anammox) has recently been recognized as a pathway for the removal of fixed N from aquatic ecosystems. However, the quantitative significance of anammox in estuarine sediments is variable, and measurements have been limited to a few estuaries. We measured anammox and conventional denitrification activities in sediments along salinity gradients in the Chesapeake Bay and two of its sub-estuaries, the Choptank River and Patuxent River. Homogenized sediments were incubated with 14/15N amendments of

Isolation and Characterization of Diverse Halobenzoate-Degrading Denitrifying Bacteria from Soils and Sediments

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Pmoa primers for detection of anaerobic methanotrophs

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Bleaching and stress in coral reef ecosystems: hsp70 expression by the giant barrel sponge Xestospongia muta

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Taxonomic characterization of denitrifying bacteria that degrade aromatic compounds and description of Azoarcus toluvorans sp. nov. and Azoarcus toluclasticus sp. nov.

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