Chemotaxis, respiratory oxidase and stringent response to carbon sources of the polychlorinated-biphenyl degrader Pseudomonas pseudoalcaligenes KF707

Sandri, Federica (2018) Chemotaxis, respiratory oxidase and stringent response to carbon sources of the polychlorinated-biphenyl degrader Pseudomonas pseudoalcaligenes KF707, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Biologia cellulare e molecolare, 30 Ciclo. DOI 10.6092/unibo/amsdottorato/8522.
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Bacteria are important for the so called “environmental bioremediation procedures” that can be defined as the use of microorganisms to degrade or transform toxic compounds. Pseudomonas pseudoalcaligenes KF707, a soil Gram negative Proteobacterium isolated near a biphenyl manufacturing plant in Japan, it is known as one of the most effective polychlorinated-biphenyls degraders. The KF707 genome analysis, has highlighted the potential capacity of this bacterium to use as carbon and energy sources an extraordinary wide spectrum of aromatic compounds. In this PhD work, several aspects of KF707 metabolism have been analyzed: The role of cheA genes in swarming and swimming motility. The genome of KF707 contains three cheA gene clusters, only the cheA1 gene is involved in swimming motility. Conversely, the swarming motility is strongly dependent on the presence of cheA2 and cheA1 genes while the cheA3 gene deletion has a negative effect on this type of bacterial movement. The modulation of the terminal respiratory oxidases in the presence of biphenyl. In the genome of KF707 five terminal oxidases were identified: two caa3-type oxidases, two cbb3-type and one cyanide-insensitive quinol oxidase. We demonstrated that not only biphenyl modulates the expression and function of the respiratory oxidases, but we also provided biochemical and structural evidence that KF707 overproduces a Caa3 oxidase in cells grown with biphenyl. The role of relA and spoT genes in KF707 stringent response mechanism. KF707 owns two proteins, RelA and SpoT, necessary for the stringent response mechanism. Deletion of these two genes affects: KF707 growth in the presence of sugars and aromatic compounds, the swarming motility, and the expression of the terminal cytochrome oxidases, that is fully disconnected from the cell growth phase and carbon source. The results gave rise to an important set of biochemical and molecular clues useful for the KF707 application in environmental technologies.


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