Biology subjects

Morris, F.

Publications and source records attributed to Morris, F..

3 recordsLinked to original sources

bioRxiv2025

Comparative analysis of shared and unique mechanisms important for diverse strains of Pasteurella multocida to cause systemic infection in mice

Pasteurella multocida is a Gram-negative bacterium that causes a range of distinct diseases in livestock animals. Different P. multocida diseases are associated with different capsule and lipopolysaccharide (LPS) types, but little else is known about what underpins this disease specificity. In this study, we utilised transposon-directed insertion site sequencing (TraDIS) to identify genes in two diverse P. multocida strains that are required for growth in rich media, and genes important for survival during systemic infections in BALB/c mice. Analysis of growth in heart infusion broth showed that the fowl cholera isolate VP161 (capsule type A and LPS type L1) and the bovine haemorrhagic septicaemia isolate M1404 (capsule type B and LPS type L2) shared 461 genes essential for growth in rich media, with 95% of these present in all publicly available closed P. multocida genomes. In vivo fitness analysis identified 63 and 94 genes important for VP161 and M1404 survival in BALB/c mice, respectively. Only 35 homologs were identified as important for survival in both strains, showing that conserved biological systems can be differentially important for different P. multocida strains. Investigation of proteins involved in the catabolite response showed that an active cyclic-adenosine monophosphate (cAMP) receptor protein (CRP) was required for maximal fitness in M1404. Furthermore, disrupting CRP or cAMP production also reduced capsule production in M1404, but increased capsule production in VP161, demonstrating that these P. multocida strains have different regulatory systems for crucial virulence factors. Author SummaryPasteurella multocida is an important livestock pathogen, causing several distinct severe diseases in many different livestock animals. P. multocida can spread rapidly throughout animal populations, with peracute infections causing death within 48 h, resulting in large outbreaks with high mortality. Host predilection and disease presentation often correlate with the capsule and lipopolysaccharide type produced by the causative strain. However, the processes that allow certain strains to cause a particular disease are not well understood. In this study, we have comprehensively identified genes required for two P. multocida strains to cause systemic infection in mice, showing that these diverse strains have differential requirements for survival during a systemic infection. This information is crucial for understanding P. multocida diseases and for the development of new strategies to combat infection.

microbiology↗

bioRxiv2020

Structure-function analyses of dual-BON domain protein DolP identifies phospholipid binding as a new mechanism for protein localisation

The Gram-negative outer membrane envelops the bacterium and functions as a permeability barrier against antibiotics, detergents and environmental stresses. Some virulence factors serve to maintain the integrity of the outer membrane, including DolP (formerly YraP) a protein of unresolved structure and function. Here we reveal DolP is a lipoprotein functionally conserved among Gram-negative bacteria and that loss of DolP increases membrane fluidity. We present the NMR solution structure for DolP, which is composed of two BON domains that form an interconnected opposing pair. The C-terminal BON domain binds to anionic phospholipids through an extensive membrane:protein interface providing evidence of subcellular localization of these phospholipids within the outer membrane. This interaction is essential for DolP function and is required for sub-cellular localization of the protein to the cell division site. The structure of DolP provides a new target for developing therapies that disrupt the integrity of the bacterial cell envelope.

biochemistry↗

bioRxiv2019

Structure-function analysis of the Escherichia coli β-barrel assembly enhancing protease BepA suggests a role for a self-inhibitory state

The asymmetric Gram-negative outer membrane (OM) is the first line of defence for the bacteria against environmental insults and attack by antimicrobials. The key component of the OM barrier is the surface exposed lipopolysaccharide, which is transported to the surface by the essential lipopolysaccharide transport (Lpt) system. Correct folding of the Lpt system OM component, LptD, is essential and is regulated by a periplasmic metalloprotease, BepA. Here we present the crystal structure of BepA, solved to a resolution of 1.9 [A]. Our structure comprises the zinc-bound m48 protease domain and a tetratricopeptide repeat (TPR) domain, consisting of four 2-helix TPR motifs and four non-TPR helices, leading to a nautilus-like shape in which the TPR repeats cup the protease domain. Using targeted mutagenesis approaches, we demonstrate that the protein is auto-regulated by the active-site plug. Further to this we reveal that mutation of a negative pocket, formed at the interface between the m48 and TPR domains, impairs BepA activity suggesting the pocket as a possible substrate binding site. We also identify a potential protein interaction site within the TPR cavity as being important for BepA function. Lastly, we provide evidence to show that increased antibiotic susceptibility in the absence of correctly functioning BepA occurs through disruption of OM lipid asymmetry, leading to reduced barrier function and increased cell permeability.

microbiology↗