Open AccessNon-Equilibrium Polar Localization of Proteins in Bacterial Cells
Author(s) -
Saeed Saberi,
Eldon Emberly
Publication year - 2013
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0064075
Subject(s) - nucleoid , polar , maxima and minima , biological system , aggregate (composite) , physics , mechanism (biology) , work (physics) , biophysics , constant (computer programming) , volume (thermodynamics) , protein aggregation , biology , chemistry , chemical physics , microbiology and biotechnology , computer science , genetics , escherichia coli , materials science , nanotechnology , gene , mathematics , thermodynamics , mathematical analysis , astronomy , programming language , quantum mechanics
Many proteins are observed to localize to the poles within bacterial cells. Some bacteria show unipolar localization, yet under different conditions bipolar patterns can emerge. One mechanism for spontaneous polar localization has been shown to involve the combination of protein aggregation and nucleoid occlusion. Whether the different observed patterns represent global energy minima for the cellular system remains to be determined. In this paper we show that for a model consisting only of protein aggregation along with an excluded volume effect due to the DNA polymer, that unipolar patterns are the global energy ground state regardless of protein concentration and DNA density. We extend the model to allow for proteins to be added to the cellular volume at a constant rate and show that bipolar (or multi-foci) patterns emerge as the result of the system being kinetically trapped in a local energy minimum. Lastly we also consider the situation of a growing cell that starts with a pre-existing aggregate at one of the poles and determine conditions under which either unipolar or bipolar patterns can exist at the point when it is ready to divide. This work sheds new interpretations on recently published experimental data and suggests experiments to test whether such a mechanism can drive patterning in bacteria.