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Academic Positions

Academic and professional award

A Systems Biology View of Microbial Developmental Networks and their Evolution
Microbial life, as ours, is shaped by their decisions. For example, when food become scarce, a microbe has to decide whether to explore other areas, scavenge local resources or become dormant (forming a resilient spore, as seen in the figure below). These decisions are often taken in complex and unpredictable environments where a wrong choice will lead to dire consequences. To diminish the uncertainty, microbes use their clonal structure to make community-based decisions by probabilistically differentiating into different cell-types, either to hedge their bets on multiple decisions or to cooperate and create more complex functional responses.
Our lab aims at gaining quantitative understanding of the regulatory and mechanistic networks underlying microbial probabilistic decision-making and its evolution at the single-cell and community levels. To this aim, we combine experimental approaches (mainly based on advanced time-lapse microscopy, genetics and directed evolution) with mathematical modeling.

Bacillus subtilis stress response network
Our main model organism is the soil bacteria Bacillus subtilis. Under stress conditions B. subtilis will employ a diverse set of responses culminating in the formation of bacterial spores – the most resilient cell type on earth. The genetic network underlying this stress response leads to functional and spatial symmetry breaking and differentiation on multiple levels:
• At the subcellular level - sporulation is started by an asymmetric division that will lead to formation of two different compartments with different genetic programs, mediated by cross-signaling.
• At the cellular level - cells will differentiate probabilistically into various cell-states depending on environmental context.
• At the multi-cellular level - cells within a colony will self-organize into complex spatial patterns with varying shape and cell-type composition.
We study various mechanistic and regulatory aspects of these processes and their evolution.

An example for evolution of sporulation (from ref. 1): (A-C) Patterns of sporulation in wild-type (A) and mutant (B) B. subtilis and in wild-type C. oceanicum (C). (A) B. subtilis wild-type cells typically sporulate with a single spore (green) associated with each mother-cell (red). (B) specific mutants reveal cells with one spore (wt) or two spores ( ‘twin’ mutant) arising from one mother cells. green dots mark chromosomes in this picture (C) The B. subtilis mutant may explain evolutionary processes underlying discrete phenotype changes (from one to two spores)as occurs in other species. (D)The developmental switch from single to ‘twin’ sporulation depends on a complex regulatory network and requires the evolution of multiple changes.

Current research interests:

• Cell-cell interaction and its relation with differentiation and pattern formation in structured B. subtilis communities.

• The development and evolution of symmetry breaking and differentiation during sporulation.

• The evolution of bet-hedging strategies.

• Micro-evolution of sporulation initiation as a probabilistic decision.

• Gene expression noise in developmental decisions.

• Super-resolution imaging of bacterial development.

Now recruiting students (Master, PhD) and post-docs from Biology, Physics and Engineering .

Come and join a multi-disciplinary research lab at the interface between evolution and development!

Please contact Dr. Eldar for details.

1. Partial penetrance facilitates developmental evolution in bacteria

Avigdor Eldar ,Vasant K. Chary, Panos Xenopoulos, Michelle E. Fontes,Oliver C. Losón, Jonathan Dworkin, Patrick J. Piggot PJ, Michael B. Elowitz.

Nature , 460(7254):510-4 (2009).

2. Determinants for the Subcellular Localization and Function of a Non-essential SEDS protein.

Gonçalo Real, Allison Fay, Avigdor Eldar , Sérgio M. Pinto, Adriano O. Henriques, and Jonathan Dworkin.

Journal of Bacteriology, 190: 363-376 (2008)

3. Interpreting clone-mediated perturbations of morphogen profile

Avigdor Eldar and Naama Barkai

Developmental Biology , 278(1), 203-7 (2005)

4. Elucidating mechanisms underlying robustness of morphogen gradients

Avigdor Eldar , Ben-Zion Shilo and Naama Barkai

Current opinion in genetics and development, 14(4), 435-9 (2004)

5. Self-Enhanced Ligand Degradation Underlies Robustness of Morphogen Gradients
Avigdor Eldar , Dalia Rosin, Ben-Zion Shilo and Naama Barkai.

Developmental Cell , Vol 5, 635-646 (2003)

6. Robustness of the BMP morphogen gradient in Drosophila embryonic patterning
Avigdor Eldar , Ruslan Dorfman, Daniel Weiss, Hilary Ashe, Ben-Zion Shilo and Naama Barkai
Nature 419, 304-308 (2002)