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Tues., Feb. 28, 2012
10 a.m.,TI Auditorium
(ECSS 2.102)












"Stochasticity & Ultrasensitivity In Bacterial Networks"
Oleg Igoshin, Assistant Professor, Dept. of Bioengineering, Rice University

Nonlinearities of rate laws describing biochemical reaction kinetics can often results in
ultrasensitive switches in which small changes or fluctuations of parameters can lead to a large change in
network output. Such switches are important for making robust cell decisions but can be detrimental for
networks functioning in homeostasis and desiring noise minimization. In this presentation I'll discuss
biological examples illustrating each of these cases. In the first story, with combination of mathematical
modeling and bioinformatic data analysis, we show that noise minimization and avoidance of ultrasensitive
switches explain operon organization of E. coli. These results suggest a central role for gene expression
noise in selecting for or against maintaining operons in bacterial chromosomes thereby providing an
example of how the architecture of post-translational networks affects bacterial evolution. In the second
story, with combination of mathematical modeling and single-cell microscopy, we show the existence and
origins of ultrasensitivity in the network responsible for cell-fate decision in sporulating B. subtilis. These
results illustrate how unique structure of the sporulation network allows fast and robust population level
response despite cellular variability.

Oleg Igoshin specializes in computational systems biology with emphasis in evolutionary
design principles and the characterization of biochemical networks, pattern formation in bacterial
biofilms, and genetic networks in bacterial and stem cell development.
Prior to joining Rice University in 2007, Igoshin was a postdoctoral researcher in the Department of
Biomedical Engineering at UC Davis working with Professor Michael Savageau (2004-2006). His research in
the modeling of pattern formation in Myxobacteria at the UC Berkeley was supported by a Howard Hughes
Medical Institute Predoctoral Fellowship (2001-2004) and Regents Fellowship (2000-2001). New research in
Igoshin's group at Rice is supported by an NSF CAREER Award for self-organization mechanisms in
Myxococcus xanthus swarms (2009) and a John S. Dunn Research Foundation award (2009). His research
into thermodynamic models of combinatorial gene regulation by distant enhancers was selected for an IET
Premium Award in Systems Biology (2011). The award is given by the journal’s editorial board members
and editors-in-chief who nominate the ‘best paper of the year’ for each journal published by Institute of
Engineering and Technology (IET).