Biology subjects

Stanley-Wall, N. R.

Publications and source records attributed to Stanley-Wall, N. R..

5 recordsLinked to original sources

bioRxiv2023

Extracellular proteases are an essential public good supporting Bacillus subtilis growth through exogenous protein degradation

Bacteria encounter polymeric nutrient sources that need to be processed to support growth. Bacillus subtilis is a bacterium known for its adaptability and resilience within the rhizosphere and broader soil environment. Here we explore the role that a suite of extracellular proteases plays in supporting growth of B. subtilis when an extracellular heterologous protein (BSA) provides an abundant, but polymeric, food source. We confirm the essential role of extracellular proteases in this context and note the influence of the polymeric nutrient concentration on the yield of growth, but not on the relative level of extracellular proteases. We demonstrate the collective action of the extracellular proteases in supporting B. subtilis growth and evidence their use as a shared public good. Furthermore, we show that B. subtilis is subjected to a public good dilemma, but only in the context of using a polymeric food source. Using mathematical simulations, we uncover that this dilemma is driven by the relative cost of producing the public good. Collectively, our findings reveal how B. subtilis can survive in environments that vary significantly in terms of immediate nutrient accessibility. This information should inform steps to improve its efficacy as a biofertilizer in agricultural settings.

microbiology↗

bioRxiv2021

A theoretical framework for multi-species range expansion in spatially heterogeneous landscapes

Range expansion is the spatial spread of a population into previously unoccupied regions. Understanding range expansion is important for the study and successful manipulation and management of ecosystems, with applications ranging from controlling bacterial biofilm formation in industrial and medical environments to large scale conservation programmes for species undergoing climate-change induced habitat disruption. During range expansion, species typically encounter competitors. Moreover, the environment into which expansion takes place is almost always heterogeneous when considered at the scale of the individual. Despite the ubiquitous nature of these features, the impact of competition and spatial landscape heterogeneities on range expansion remains understudied. In this paper we present a theoretical framework comprising two competing generic species undergoing range expansion and use it to investigate the impact of spatial landscape heterogeneities on range expansion with a particular focus on its effect on competition dynamics. We reveal that the area covered by range expansion during a fixed time interval is highly variable due to the fixed landscape heterogeneities. Moreover, we report significant variability in competitive outcome (relative abundance of a focal species) but determine that this is induced by low initial population densities, independent of landscape heterogeneities. We further show that both area covered by range expansion and competitive outcome can be accurately predicted by a Voronoi tessellation with respect to an appropriate metric, which only requires information on the spatial landscape and the response of each species to that landscape. Finally, we reveal that if species interact antagonistically during range expansion, the dominant mode of competition depends on the initial population density. Antagonistic actions determine competitive outcome if the initial population density is high, but competition for space is the dominant mode of competition if the initial population density is low.

ecology↗

bioRxiv2021

Founder cell configuration drives competitive outcome within colony biofilms

Bacteria typically form dense communities called biofilms, where cells are embedded in a self-produced extracellular matrix. Competitive interactions between strains within the biofilm context are studied due to their potential applications in biological, medical, and industrial systems. Combining mathematical modelling with experimental assays, we reveal that the spatial structure and the competitive dynamics within biofilms are significantly affected by the location and density of founder cells. Using an isogenic pair of Bacillus subtilis strains, we show that the observed spatial structure and relative strain biomass in a mature biofilm can be mapped directly to the locations of founder cells. Moreover, we define a predictor of competitive outcome that accurately forecasts relative abundance of strains based solely on the founder cells access to free space. Consequently, we reveal that variability of competitive outcome in biofilms inoculated at low founder density is a natural consequence of the random positioning of founding cells in the inoculum. Extending our study to non-isogenic strain pairs of B. subtilis, we show that even for strains with different antagonistic strengths, a race for space remains the dominant mode of competition in biofilms inoculated at low founder densities. Our results highlight the importance of spatial dynamics on competitive interactions within biofilms and hence to related applications.

microbiology↗

bioRxiv2020

Density and temperature controlled fluid extraction in a bacterial biofilm is determined by poly-γ-glutamic acid production

A hallmark of microbial biofilms is the self-production of extracellular matrix that encases the cells resident within the community. The matrix provides protection from the environment, while spatial heterogeneity of expression influences the structural morphology and colony spreading dynamics. Bacillus subtilis is a model bacterial system used to uncover the regulatory pathways and key building blocks required for biofilm growth and development. Previous reports have suggested that poly-{gamma}-glutamic acid (PGA) production is suppressed during biofilm formation and does not play a major role in biofilm morphology of the undomesticated isolate NCIB 3610. In this work we report on the observation of multiple travelling fronts that develop during the early stage of B. subtilis colony biofilm formation. We find the emergence of a highly motile population of bacteria that is facilitated by the extraction of fluid from the underlying agar substrate. Motility develops behind a moving front of fluid that propagates from the boundary of the biofilm towards the interior. The extent of proliferation is strongly modulated by the presence of extracellular polysaccharides (EPS). We trace the origin of this moving front of fluid to the production of PGA. We find that PGA production is correlated with higher temperatures, resulting in a mature biofilm morphology that is distinct from the biofilm architecture typically associated with B. subtilis. Our results suggest that B. subtilis NCIB 3610 produces distinct biofilm matrices in response to environmental conditions.

microbiology↗

bioRxiv2016

Evolutionary variations in the biofilm-associated protein BslA from the genus Bacillus

BslA is a protein secreted by Bacillus subtilis which forms a hydrophobic film that coats the biofilm surface and renders it water-repellent. We have characterised three orthologues of BslA from Bacillus amyloliquefaciens, Bacillus licheniformis and Bacillus pumilus as well as a paralogue from B. subtilis called YweA. We find that the three orthologous proteins can substitute for BslA in B. subtilis and confer a degree of protection, whereas YweA cannot. The degree to which the proteins functionally substitute for native BslA correlates with their in vitro biophysical properties. Our results demonstrate the use of naturally-evolved variants to provide a framework for teasing out the molecular basis of interfacial self-assembly.

microbiology↗