Master's Defense

An Exploratory Study of Cell Growth and Division Data

Speaker:Tong Niu
tn9td at
Date: Thursday, September 22, 2016
Time: 10:30am - 12:00pm
Location: D344 LSRC, Duke


Understanding the mechanism behind cell size control of bacteria such as E. coli has been an active research topic for decades. Until about 2010, most studies were limited to measurements at the cell population level. Recently advanced technologies, including Mother Machine and modern microscopes, as well as new biological insights and experiment techniques enable measurements of cell growth and division at individual cell level with high spatial and temporal resolution. These unprecedented data allowed scientists to take closers looks into the patterns of cell growth and division, to ask and answer new questions, and to gain a better understanding of the natural law governing cell growth. The thesis study is based on six data sets provided by You lab at Duke University and by Jun lab at University of California, San Diego. We focus on explorative and quantitative study of inter-generation relationships among certain cell growth parameters and variables, and equally important, the variation in each relationship.

We report and describe three particular findings. (1) The variation in cell size at birth between two successive generations, i.e., mother and daughter generations, is better captured in two separate zones in the mother-daughter plane of initial cell size. This leads to a bifurcated linear model with much narrower noise spread. The model can be used to connect or compensate for certain well-known models. (2) The variation in doubling time between two successive generations is confined in a finite region with non-uniform density. Specifically, the confining region is apparently triangular in the successive-generation plot of doubling time. The highest variation of doubling time in daughter-generation corresponds to the median for the mother- generation. This variation structure of successive-generation is further used to predict the variations in succeeding generations, via an iterative simulation method. (3) The relationship between cell size and doubling time is studied with Fourier analysis. We found that the two dominant frequencies of the cell-size time series are nearly constant for each lineage. Furthermore, the top dominant frequency location is invariant under random re-ordering of generations. This invariance suggests that the dominant frequency is an intra-generation property, i.e., an inherent property. These findings are descriptive rather than explanatory. Nonetheless, they provide additional angles to exam, re-exam and improve our understanding of cell growth control mechanism. The findings also show, perhaps in a subtle way, the effect of computational concepts and techniques, which we used to probe into data, on the resulting models.

Advisor(s): Xiaobai Sun
Committee members: Nikos Pitsianis, Nicolas Buchler, Lingchong You