Lawrence Berkeley National Laboratory

Desulfovibrio vulgaris Hildenborough (DvH), a sulfate reducing bacterium, has historically been an environmentally important bacterium due its role in bio-corrosion of oil and gas pipelines and is one of the major sources of H2S that cause bio-fouling of petroleum. Another reason for interest in DvH is due to its ability to reduce toxic and radioactive metals to their lower oxidation and insoluble forms, and therefore its potential use in bioremediation. While sulfate typically serves as the electron acceptor in DvH, alternate candidates for electron acceptors such as nitrate also exist. Exposure to excess nitrate occurs frequently since it is a common co-contaminant along with metals such as uranium in many waste sites. Therefore our knowledge of DvH response to nitrate will undoubtedly be critical in developing bioremediation strategies. This poster presents the results from a quantitative proteomic analysis evaluating the response of DvH to nitrate stress. Control proteome was compared with proteome from cells exposed to NaNO3 levels that cause a 50% inhibition in growth. The ITRAQ peptide labeling strategy coupled with tandem liquid chromatography and mass spectrometry (triple-quad time of flight) was used. A total of 1166 unique proteins were identified, representing 34% of the total DvH proteome and spanning every functional category. Our results indicate that this was a mild stress, as confirmed by the lack of change observed in central metabolism or in the sulfate reduction pathway. Increases seen in transport systems for proline, glycine betaine and glutamate indicate that the NaNO3 exposure led to both salt stress and nitrate stress. Up-regulation observed in a large number of ABC transport systems as well as in iron-sulfur cluster containing proteins, however, appear to be specific to the exposure to nitrate. Finally, a number of hypothetical proteins are among the most significant changers, indicating that there may be unknown mechanisms initiated upon n