Oral Presentation Australian Microbial Ecology 2017

Bacteria push the limits of sensory precision to navigate dynamic seascapes (#3)

Douglas R Brumley 1 , Francesco Carrara 1 , Andrew M Hein 2 , Yutaka Yawata 1 , Simon A Levin 2 , Roman Stocker 1
  1. Institute for Environmental Engineering, ETH Zurich, Zurich, Switzerland
  2. Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA

Dense, ephemeral aggregations of bacteria are ubiquitous in the ocean, where they serve as hotbeds of metabolic activity, nutrient cycling, and horizontal gene transfer. A prevailing view is that these aggregations form when motile bacteria use chemotaxis to navigate towards chemical hotspots. However, the limited precision of chemosensory systems places fundamental constraints on organismal performance. An open question is whether organisms are routinely pushed to these limits, and how limits might influence interactions between populations of organisms and the environment.

Here, we use a novel experimental platform, which implements the photorelease of caged glutamate through illumination with a LED beam, to create realistic, replicable, sub-millimetre scale nutrient pulses within a microfluidic device. Through high-speed tracking of freely moving bacteria and a new mathematical theory, we show that sensory noise ultimately limits when and where bacteria can detect and climb chemical gradients. Our results suggest that bacteria inhabit chemical landscapes that are typically dominated by noise that masks shallow chemical gradients, and that the spatiotemporal dynamics of bacterial aggregations can be predicted by mapping the region where chemical gradients rise above noise. More generally, our results demonstrate that fundamental physical limits on sensing accuracy can provide a powerful tool for predicting the location, spatial extent, and lifespan of bacterial aggregations in highly dynamic natural environments, such as those they encounter in the ocean.

  1. Son K, Brumley DR, Stocker R (2015) Live from under the lens: exploring microbial motility with dynamic imaging and microfluidics. Nature Reviews Microbiology 13(12):761–775.
  2. Brumley DR, Rusconi R, Son K, Stocker R (2015) Flagella, flexibility and flow: physical processes in microbial ecology. European Physical Journal Special Topics 224:3119–3140.
  3. Hein AM, Brumley DR, Carrara F, Stocker R, Levin SA (2016) Physical limits on bacterial navigation in dynamic environments. Journal of The Royal Society Interface 13:20150844.