Modeling bacterial behavior
Single cells

How well can we predict bacterial behavior?

Chemotaxis Web App Documentation

The ability of bacteria to move toward favorable conditions is an emergent property of their chemotaxis signaling pathways. The system has to be considered as a whole to understand how few proteins can generate complex behaviors. In addition, because chemotactic behavior conditions the sensory inputs, predicting how bacteria navigates complex environments is not trivial. We use mathematical modeling and simulations to examine how biochemical parameters determine chemotactic performance in various environments.

Phenotypic switching in Vibrio cholerae

How do clonal populations generate phenotypic diversity?

Vibrio cholerae integrate environmental signals through a sophisticated signaling network to control its transition between motile and biofilm lifestyles. In some environments, clonal populations generate both motile and sessile cells, presumably as a bet hedging strategy. We are investigating the role of the secondary messenger c-di-GMP in controlling phenotypic diversity in Vibrio cholerae using a combination of mathematical modeling, single-cell fluorescence microscopy, and tracking.

Flagellar motility through mucus

How do pathogenic bacteria compromise the host mucus defense?

The mucosal tissues covering the gastrointestinal, respiratory, reproductive, and urinary tracts are the places of residence of much of our microbiota. The mucus layer is also an important physical barrier against invasion by pathogens. We are investigating how flagellar motility enables Vibrio cholerae, Salmonella enterica, and Campylobacter jejuni to penetrate intestinal mucus. Using single-cell tracking and microrheology, we are characterizing both bacterial behavior and the physical characteristics of the mucus matrix.

Fitness trade-offs in flagellar motility

How many flagella is enough?

Bacteria have evolved a wide diversity of flagellar arrangements with species expressing from one flagellum to dozens, positioned at the cell poles or over the cell body. The number of flagella can also vary between cells within a population. The evolutionary constraints shaping the diversity of flagellar expression and cell behaviors are poorly understood. By controlling flagellar expression, directed evolution, and competition experiments, we are investigating the tradeoffs of making more than one flagellum in different environments.

Micrometer obstacle course
Single cells

How do bacteria find their way in a rough world?

Natural environments contain physical obstacles, whether that is the mucus in the gut or aggregates in the soil. We have a good understanding of chemotaxis in simple chemical gradients, but observing bacterial behavior in natural environments to observe how bacteria circumvent obstacles is difficult. We are developing microfluidics mazes and gradient generators to investigate the constraints imposed by physical obstacles at different length-scales on chemotactic performance.

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