Use this URL to cite or link to this record in EThOS:
Title: Regulation of the expression and positioning of chemotaxis and motor proteins in Rhodobacter sphaeroides
Author: Wilkinson, David Arthur
ISNI:       0000 0004 2709 1280
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2010
Availability of Full Text:
Access from EThOS:
Full text unavailable from EThOS. Please try the link below.
Access from Institution:
Bacteria achieve directed motion through their environments by integrating propulsion with chemical detection in the process of chemotaxis. Central to this process are the macromolecular protein structures of the flagellar motor and the chemoreceptor arrays, which are responsible for motility and chemical sensing, respectively. These protein complexes localise to different discrete subcellular positions in different bacterial species, and their correct subcellular localisation is often essential to their function. In the monotrichous α‐proteobacterium Rhodobacter sphaeroides, the flagellum is subpolar and two distinct sets of chemotaxis proteins localise to discrete polar and cytoplasmic positions within the cell. In this study, the development of software for the analysis of fluorescent microscopy images allowed cellular morphologies and the localisation and distribution of the chemoreceptor arrays of R.sphaeroides to be characterised in detail, showing that protein partitioning at cell division results in an asymmetric separation of both cytoplasmic and membrane‐bound protein components between daughter cells. The design of a fluorescence‐based assay for the analysis of gene expression assisted in demonstrating that expression of both the chemotaxis and motor genes of R.sphaeroides is regulated by the sigma factor, FliA, and its inhibitor, FlgM. FliA was then used to achieve varying expression of the chemotaxis genes, and the concentration dependence of array clustering was explored in microscopy images, revealing important differences between cluster formation in R.sphaeroides and other species. Additionally, FliA was identified as a regulator of flagellar number in R.sphaeroides, controlling a negative feedback‐loop in the hierarchy of flagellar assembly that represses flagellar formation upon secretion of FlgM. The complex regulatory pathway controlling R.sphaeroides flagellar assembly is the first identified system where completion of a single flagellum directly inhibits the production of a second, a mechanism that may be important to many monotrichous bacterial species.
Supervisor: Armitage, Judy P. Sponsor: Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Biochemistry ; Rhodobacter sphaeroides ; FliA ; FlgM ; gene expression ; microscopy