Molecular mechanisms of nitric oxide induced Pseudomonas aeruginosa biofilm dispersal

Abstract

Bacteria are able to transition between a single celled, planktonic lifestyle and a communal, antibiotic tolerant phenotype known as a biofilm. The ability of bacteria to transition between resistant and virulent behaviours underpins a number of chronic infections and is regulated by levels of the secondary messenger cyclic dimeric guanosine monophosphate (c-di-GMP). A number of external stimuli are able to modulate the levels of intracellular c-di-GMP and induce biofilm formation or dispersal. Nitric oxide (NO) is one such stimulus, able to induce biofilm dispersal in Pseudomonas aeruginosa, although the nature of NO detection, and how this couples to reduced levels of c-di-GMP is currently unknown.

Chapter 1 describes the current knowledge available in literature about biofilm dispersal, potential sensors of NO and enzymatic domains that regulate c-di-GMP concentrations. Chapter 2 details the methodologies used within this work to structurally and biochemically characterise potential NO sensors. Chapter 3 describes attempts to crystallise the transmembranous sensor protein Mucoid alginate regulator (MucR). Structural characterisation of the c-di-GMP catabolising enzyme domain within MucR, and contrast to equivalent domains in other proteins, offers new insight into how this process may be regulated. Chapter 4 describes the spectroscopic characterisation of NO binding to the protein Biofilm dispersal locus A (BdlA). Crystal structures of the apo-form of BdlA are used to propose models of how NO binding may go on to induce biofilm dispersal. Chapter 5 details how bioinformatics strategies, coupled to established knowledge of enzyme architectures and related phenotypes, can be used to identify further proteins that may serve to bind NO. Understanding the molecular details of NO-induced biofilm dispersal could lead to the development of novel therapies to treat biofilm infections when used in conjugation with conventional antibiotics.

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Identifiers

ORCID for Ivo Tews: orcid.org/0000-0002-4704-1139

ORCID for Jeremy Webb: orcid.org/0000-0003-2068-8589

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