Papers

For full list of our latest papers please, please see Mack's Google Scholar page.

Highlights of featured papers from our group:

Bacteria use spatial sensing to direct chemotaxis on surfaces

Nature Microbiology

In this study, we overturned the long held idea that bacteria are too small to sense chemical gradients along the length of their cell bodies.  This work suggests that even stationary cells in densely packed biofilms can active sense their chemical environment, which has wide ranging implications on biofilm development and the strategies we use to manipulate them.

Further information

• Read the paper

• University of Sheffield press release

Collectively moving bacteria and cancer cells generate "universal" behaviour

Nature Physics

In this paper, we show that the flows generated by collectively moving bacteria, dog kidney cells, and human breast cancer cells all exhibit the same "universal" features.  Interestingly, these features have excellent agreement with predictions from an intensively studied area of mathematics and suggest that all of these very different biological systems are poised at so-called "critical state".  

Further information

• Read the paper

Bacteria commit suicide by migrating towards clinical antibiotics

Nature Communications

Bacteria are generally though to chemotax towards nutrients and away from toxins.  In this study, we demonstrate that surface attached pathogen (P. aeruginosa) surprisingly migrate TOWARDS the clinical antibiotics used to treat them and this leads to their ultimate demise.  We then study the response to secretions from competing strains to help understand how this "fatal attraction" towards antibiotics has evolved.

Further information

• Read the paper

Bacteria solve the problem of crowding by moving slowly

Nature Physics

Chain formation can enhance the vertical migration of phytoplankton through turbulence

Science Advances

Many species of motile phytoplankton can actively form long multicellular chains by remaining attached to one another after cell division. 

While chains swim more rapidly than single cells of the same species, chain formation also markedly reduces phytoplankton’s ability to maintain their bearing. This suggests that turbulence, which acts to randomise swimming direction, could sharply attenuate a chain’s ability to migrate between well-lit surface waters during the day and deeper nutrient-rich waters at night. 

Here, we use numerical models to investigate how chain formation affects the migration of phytoplankton through a turbulent water column. 

Unexpectedly, we find that the elongated shape of chains helps them travel through weak to moderate turbulence much more effectively than single cells, and isolate the physical processes that confer chains this ability. 

Our findings provide a new mechanistic understanding of how turbulence can select for phytoplankton with elongated morphologies and may help explain why turbulence triggers chain formation.

Further information

• Read the paper

A model of strongly biased chemotaxis reveals the trade-offs of different bacterial migration strategies

Mathematical Medicine and Biology

Recent experiments from our group demonstrated swimming and biofilm bacteria employ fundamentally different strategies to generate chemotaxis: swimming cells typically suppress reorientations when moving up a chemoattractant gradient, whereas biofilm cells increase reorientations when moving down a chemoattractant gradient. The reason for this difference remains unknown. 

Here we develop a mathematical framework to understand how these different chemotactic strategies affect the distribution of cells at the population level. 

Current continuum models typically assume a weak bias in the reorientation rate and are not able to distinguish between these two strategies, so we derive a model for strong chemotaxis that resolves how both the drift and diffusive components depend on the underlying chemotactic strategy. 

This new model reveals that the strategy employed by swimming cells yields a larger chemotactic drift, but the strategy used by biofilm cells allows them to more tightly aggregate where the chemoattractant is most abundant. 

This new modelling framework provides new quantitative insights into how the different chemical landscapes experienced by swimming and biofilm cells each selects for a different way to generate chemotaxis.

Further information

• Read the paper

Microbial competition in porous environments can select against rapid biofilm growth

Proceedings of the National Academy of Sciences, USA

Approximately 97% of bacteria on Earth live in porous environments like soil, sediments, and aquifers where they form surface attached biofilms. In this paper, we use microfluidic experiments, mechanistic models, and evolutionary game theory to show that these bacteria face a fundamental dilemma. 

In porous environments cells rely on flow for nutrients and dispersal, however, as they grow they tend to reduce to their access to flow, diverting it instead to competitors. The interaction between biofilms and porous media hydrodynamics thus select for bacteria that grow more slowly, which stands in sharp contrast with classical theory. 

These new insights may give us the tools to rationally engineer microbial communities for important functions, like cleaning up polluted water or enhancing oil extraction.

Further information

• Read the paper (PDF, 23.4MB)

• See the Letter to Editor in PNAS by Baveye and Darnault (PDF, 510KB) and our response (PDF, 514KB)

• Highlighted in Trends in Microbiology

• Spotlighted in Chemical Research in Toxicology

• Highlighted on the HFSP homepage

Single-cell chemotaxis during biofilm formation

Proceedings of the National Academy of Sciences, USA

Bacteria living in surface attached structures known as biofilms play a central role in human infection and facilitate many important processes in the environment. 

In this paper, we show that single attached cells can sense chemical gradients and use this information to guide their movement along surfaces using tiny grappling hooks called pili. This ability allows cells to move to greener pastures, where food is more abundant. 

This work sheds new light into how biofilms function and presents a new tool to manipulate them to our advantage.

Further information

• Read the paper (PDF, 12.4MB)

• Recommended Article by Faculty of 1000