How do bacteria glide? A structural perspective into the gliding motility of Bdellovibrio bacteriovorus

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Mead, Liam Richard (2024). How do bacteria glide? A structural perspective into the gliding motility of Bdellovibrio bacteriovorus. University of Birmingham. Ph.D.

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Abstract

Bdellovibrio bacteriovorus is a bacterial predator that invades and kills Gram-negative bacteria. B. bacteriovorus’s ability to kill pathogenic strains highlights the possibility of its use as a therapeutic and biocontrol agent. Motility is key for efficient predation; B. bacteriovorus uses gliding motility to traverse biofilms in search of prey and to escape the exhausted prey cell. Gliding is controlled by cGAMP signalling which regulates the
formation of an envelope-spanning gliding machinery called the Agl-Glt complex. Whilst genetic, microscopy and interaction studies have provided initial insights into the assembly of the gliding machinery, the mechanisms by which the proteins of the Agl-Glt complex interact to facilitate gliding remain to be uncovered.

This work primarily focusses on the structural characterisation of the components of the Agl-Glt complex. The primary targets for this study are GltD1 and GltE1, periplasmic components of the Agl-Glt complex proposed to transduce force across the cell envelope. We demonstrate that GltD1 and GltE1 interact with nanomolar affinity and present the crystal structures of GltE1 and the complex of GltD1:GltE1. The GltD1:GltE1 complex provides the first structural insights into the connectivity within the Agl-Glt complex and provides information on orientation of the Agl-Glt complex in the cell envelope. A secondary focus of this study was on Bd1996 and MglA, proteins associated with the regulation of gliding motility. We experimentally confirmed that the PilZ domain of Bd1996 binds to both c-di-GMP and cGAMP, which represents the first case of a PilZ domain with dual affinity for both second messengers. We also present a combined experimental and computational characterisation of the ras-like GTPase MglA and reveal that MglA undergoes GTP dependent conformational changes to interact with binding partners. Finally, we present the crystal structure of Bd1431, a nuclease belonging to the staphylococcal nuclease family, that is upregulated during invasion. Bd1431 contains a novel dimeric fold previously unseen in the staphylococcal nuclease family.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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