Biophysical Society Thematic Meeting| Santa Cruz 2018

Genome Biophysics: Integrating Genomics and Biophysics to Understand Structural and Functional Aspects of Genomes

Monday Speaker Abstracts

Bacterial Decision-making Operating Through Tunable Binary Genetic Switches Charles J Dorman 1 1 Trinity College Dublin, Microbiology, Dublin, Dublin, Ireland Populations of genetically identical bacterial cells manage to generate cell-to-cell physiological diversity through stochastic processes operating at the level of gene expression. This seems to be an important strategy when confronted with an unpredictable and potentially hostile external environment: if things change suddenly, at least a few members of the population may be prepared and will survive the new challenge to transmit their genes vertically to future generations. We have studied a genetic switch in the model bacterium Escherichia coli that seems to operate in a random way, switching on or off a set of genes that encode a surface structure that attaches E. coli to solid surfaces. Swimming (planktonic) E. coli can switch to surface attachment if they no longer have sufficient energy to keep moving. The attached lifestyle also lends itself to physical and chemical stress survival. On closer inspection, we have found that the genetic switch can become biased toward its 'on' state in response to a deteriorating environment, overriding random switching. This biasing involves adjustments to the topology of the DNA in the bacterium and contributions by DNA structuring proteins that drive more and more of the switches across the population into the 'on' state. In addition to describing the molecular mechanisms at work in this specific switch, evidence will be presented that variable DNA topology is used quite generally to bias switching outcomes in bacteria, including pathogenic bacteria.

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