Browsing by Author "Booth, Sean C."

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    Chemical, Physiological and Metabolic Interactions between Pseudomonas, Metals and Environmental Nutrients
    (2017) Booth, Sean C.; Turner, Raymond J.; Weljie, Aalim; Gieg, Lisa; Turner, Raymond J.; Eltis, Lindsay; DeVinney, Rebekah
    Environmental pollution is one of the major problems facing humanity. Bacteria are capable of removing pollutants from the environment through their metabolic activities. This works for organic pollutants, but metals inhibit the degradation process. Pseudomonas pseudoalcaligenes KF707 is a bacterium that is resistant to metals and is able to degrade pollutants such as polychlorinated biphenyls. In this thesis I present how interactions between the bacterium, its environment and metals affect the bacterium’s physiology and metabolism of biphenyl. Chemical interactions with environmental components affect the toxicity of metals towards bacteria. By examining the tolerance of Pseudomonas species towards copper and aluminium in different media compositions I found that metal bioavailability and carbon source quality had a strong influence on the amount of metal they could withstand. Building on these data, I used metabolomics to understand how metals interfere with organic pollutant degradation. By quantifying the small molecules used and produced by the bacterial cell I was able to determine that metal toxicity is exacerbated by the oxidative stress of metabolizing an organic pollutant. P. pseudoalcaligenes KF707 can swim towards biphenyl but it was unknown how. By deleting genes that were expected to be involved in energy-taxis, a process that allows bacteria to swim to metabolizable carbon sources, I found that this was not how KF707 swims towards biphenyl. I did discover that some unexpected genes were involved in energy-taxis and also that the primary gene for this behavior, Aer, is actually a family of receptors with variable phylogenetic distribution in the genus Pseudomonas. These results provide new insight into the interactions between a bacterium and the nutrients and stressors in their environment.
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    Metabolomics reveals differences of metal Toxicity in cultures of Pseudomonas pseudoalcaligenes KF707 grown on different carbon sources
    (Frontiers, 2015-08-17) Booth, Sean C.; Weljie, Aalim M.; Turner, Raymond J.
    Co-contamination of metals and organic pollutants is a global problem as metals interfere with the metabolism of complex organics by bacteria. Based on a prior observation that metal tolerance was altered by the sole carbon source being used for growth, we sought to understand how metal toxicity specifically affects bacteria using an organic pollutant as their sole carbon source. To this end metabolomics was used to compare cultures of Pseudomonas pseudoalcaligenes KF707 grown on either biphenyl or succinate as the sole carbon source in the presence of either aluminum or copper. Using multivariate statistical analysis it was found that the metals caused perturbations to more cellular processes in the cultures grown on biphenyl than those grown on succinate. Aluminum induced many changes that were indicative of increased oxidative stress as metabolites involved in DNA damage and protection, the Krebs cycle and the production of NADPH were altered. Copper also caused metabolic changes that were indicative of similar stress, as well as appearing to disrupt other key enzymes such as fumarase. Additionally, both metals caused the accumulation of biphenyl degradation intermediates indicating that they interfered with biphenyl metabolism. Together these results provide a basic understanding of how metal toxicity specifically affects bacteria at a biochemical level during the degradation of an organic pollutant and implicate the catabolism of this carbon source as a major factor that exacerbates metal toxicity.