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Title: Regulatory genetics of cell morphology, motility and polarity in Bdellovibrio bacteriovorus
Author: Milner , David Stephen
ISNI:       0000 0004 6351 9811
Awarding Body: University of Nottingham
Current Institution: University of Nottingham
Date of Award: 2014
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Bdellovibrio bacteriovorus invade Gram-negative bacteria in a predatory process requiring type IV pili (T4P) at a single invasive pole. Bdellovibrio can encounter prey cells by flagellar motility in liquid culture, or by adventurous gliding motility on a solid surface. After T4P-mediated prey-invasion into the periplasm, the Bdellovibrio degrades the prey-cell nutrients to grow from both poles as a filament inside a now-rounded prey cell or ‘bdelloplast’. The growing Bdellovibrio cell must then partition DNA and proteins along a multi­nucleoid filament, before synchronous septation generates either an even or odd number of vibroid progeny. My thesis project investigated the control of cell morphology, polarity and surface motility in Bdellovibrio bacteriovorus. This study first focused on DivIVA, a protein involved in a variety of processes including polar peptidoglycan synthesis, control of cell morphology and control of septum formation at mid-cell in other bacteria. The Bdellovibrio DivIVA homologue was shown to have an important role in maintaining cell morphology, with fluorescent localisation and gene deletion studies suggesting that DivlVABd is likely to be involved in directing peptidoglycan synthesis, and could also play a role in septum biosynthesis. The product of a parA gene (bd3906), encoded adjacent to the Bdellovibrio ParB homologue and shown to be essential in Bdellovibrio by a previous study, was shown here to be involved in the ‘canonical’ Par role of Bdellovibrio chromosome partitioning. The function of ‘orphan’ ParA1 (Bd1326), so called because of the lack of a neighbouring parB gene, requires further investigation, though co-transcription of parA1 with neighbouring gene bolA, could implicate ParA1 as involved in the switch between Bdellovibrio growth and division. The ‘orphan’ ParA2 protein (Bd2331) was found by mutagenesis and fluorescent tagging to be involved in the regulation of reversals during Bdellovibrio adventurous gliding motility. When ParA2 was present at both poles of a Bdellovibrio cell, the cell was unable to glide on a surface, implicating ParA2 as involved in the inhibition of gliding motility. Concordant with this, deletion of parA2 resulted in cells which made more frequent reversals during gliding motility
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available