Direct Correlation between Motile Behavior and Protein Abundance in Single Cells.
Understanding how stochastic molecular fluctuations affect cell behavior requires the quantification of both behavior and protein numbers in the same cells. Here, we combine automated microscopy with in situ hydrogel polymerization to measure single-cell protein expression after tracking swimming behavior. We characterized the distribution of non-genetic phenotypic diversity in Escherichia coli motility, which affects single-cell exploration. By expressing fluorescently tagged chemotaxis proteins (CheR and CheB) at different levels, we quantitatively mapped motile phenotype (tumble bias) to protein numbers using thousands of single-cell measurements. Our results disagreed with established models until we incorporated the role of CheB in receptor deamidation and the slow fluctuations in receptor methylation. Beyond refining models, our central finding is that changes in numbers of CheR and CheB affect the population mean tumble bias and its variance independently. Therefore, it is possible to adjust the degree of phenotypic diversity of a population by adjusting the global level of expression of CheR and CheB while keeping their ratio constant, which, as shown in previous studies, confers functional robustness to the system. Since genetic control of protein expression is heritable, our results suggest that non-genetic diversity in motile behavior is selectable, supporting earlier hypotheses that such diversity confers a selective advantage.
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut, United States of America.|Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, United States of America.
Yann S
0000-0003-0244-0192
YS
Dufour
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut, United States of America.
Sébastien
S
Gillet
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut, United States of America.
Nicholas W
NW
Frankel
Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.|Department of Biomedical Engineering, University of Wisconsin-Madison, Madison, Wisconsin, United States of America.
Douglas B
DB
Weibel
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut, United States of America.|Department of Physics, Yale University, New Haven, Connecticut, United States of America.
Thierry
0000-0002-6746-6564
T
Emonet
D002633:Chemotaxis / Q000502:physiology*; D019295:Computational Biology; D004926:Escherichia coli / Q000378:metabolism* / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000032:analysis* / Q000378:metabolism; D008780:Methyltransferases / Q000032:analysis / Q000378:metabolism; D059010:Single-Cell Analysis
D029968:Escherichia coli Proteins; C513923:CheR protein, E coli; D008780:Methyltransferases