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Open Seminar March 28, 2017, 14:00

Open Seminars of the Research Group on


Stochasticity and Control in the Dynamics and Diversity of Immune Repertories: an Example of Multi-Cellular Co-Operation


Tuesday, March 28, 2017, 14:00

at the Israel Institute for Advanced Studies, Room 128



Bacterial Decision Making on Unsaturated Surfaces


Nadav Kashtan (The Hebrew University)


Bacteria respond and adapt to their environment by various means, one of the most apparent is the choice between surface-attached biofilm and solitary planktonic lifestyles. These distinct states impose tradeoffs between growth and survival which affect the fitness of individual cells under different conditions. Here, we ask how and to what extent an information-based decision to change states can improve bacterial fitness in fluctuating hydration conditions. To study this question, we use the phyllosphere – the above-ground parts of plants – as a model system. The phyllosphere is a huge microbial habitat dominated by leaf surfaces, where bacterial cells are observed either as solitary cells or within aggregates. These bacteria confront significant diel changes in hydration conditions (wet nights and dry days). We use an individual-based model to simulate bacterial colonization of a leaf surface. Simulated bacterial cells may attach or detach to/from the surface, switching between planktonic and biofilm states. The motile planktonic bacteria grow faster but have lower survival rates during dry periods. In contrast, bacteria in large aggregates grow slower, but gain a higher resistance to desiccation. In our model, attachment of a cell to the surface can occur either stochastically or by a simple preferential attachment strategy, cued by quorum-sensing signals, which provide information about the local density of bacteria on the surface at the microscale. We demonstrate that at conditions typical to the leaf surface the preferential attachment strategy carries a large fitness advantage over any stochastic strategy. The emergent collective ability to regulate the dynamics of the aggregate-size distribution, which arises from the individual behavior of cells, proves critical at the early colonization stages. We argue that the resulting partition of planktonic and biofilm states and the dynamics of spatial organization can be conceptualized as resource allocation optimization.


Related Research Questions


1. Can we predict the spatial organization and dynamics of complex surface-related bacterial communities?
2. How does single-cell behavior control emergent collective properties of bacterial populations?
3. What is the selective advantage of given individual bacterial behaviors that control collective properties of the population?

Suggested Reading


Microbiology of the phyllosphere: a playground for testing ecological concepts.

Meyer KM, Leveau JH

Oecologia, 168: 621 (2012)


Differential survival of solitary and aggregated bacterial cells promotes aggregate formation on leaf surfaces

J.-M. Monier and S. E. Lindow

PNAS, 100 (26) 15977-15982 (2003)


The sociobiology of biofilms

Nadell CD, Xavier JB, Foster KR.

FEMS Microbiol Rev, 33 (1): 206-224 (2009)


Phenotypic diversity, population growth, and information in fluctuating environments.

Kussell E, Leibler S.

Science, 309 (5743), 2075-2078 (2005)



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