Bordetella pertussis is the causative agent of whooping cough, which, despite the existence of an efficacious vaccine, continues to cause disease and death worldwide. The Bvg two-component system controls much of virulence and when Bvg is active virulence factors are expressed (Bvg+), and when it is not active they are not (Bvg-). The Bvg regulon is large and much is still not understood about what it controls other than virulence. Spontaneous mutation of the Bvg system leads to the rise of Bvg- mutants, which out-compete other bacteria in culture, showing that the Bvg- phase B. pertussis has a growth advantage. The metabolism of Bvg+ B. pertussis is well characterised, but is not well understood in the Bvg- phase.Through phenotypic assays it is shown that B. pertussis in the Bvg- phase grows and divides quicker, despite Bvg+ growth consuming more glutamate per gram of biomass and also generating a greater PMF. RNAseq reveals a difference in the way that glutamate is used as a carbon source as well as different expression levels of enzymes involved in the TCA cycle and electron transport chain. TraDIS shows that genes involved in elongation of the cell wall were essential for growth in the Bvg- phase.These data point towards a model for growth whereby in the Bvg+ phase more glutamate is used in the TCA cycle for synthesis of branched-chain amino acids and reducing power, which is used in a electron transport chain to generate a greater PMF and more ATP. Cells in the Bvg- phase elongate faster to divide more often and there is a greater emphasis on synthesising aminosugars as peptidoglycan precursors, gluconeogenesis and maintaining pools of CoA.Potential for using data gained about the growth and metabolism of the Bvg- phase to improve vaccine cultures are discussed.
|Date of Award||16 Nov 2017|
|Supervisor||Andrew Preston (Supervisor)|