Seminar by Suckjoon Jun

Mechanistic Origin of Cell-Size Control and Homeostasis: Lessons from Bacteria

Seminar by Suckjoon Jun (UCSD)

Evolutionarily divergent bacteria share a common phenomenological strategy for cell-size homeostasis under steady-state conditions. In the presence of inherent physiological stochasticity, cells following this “adder” principle passively return to their steady-state size by adding a constant volume between birth and division, regardless of their size at birth. However, the mechanism of the adder has been unknown despite intense efforts. In this talk, I will explain the adder is a direct consequence of two general processes in biology: (1) threshold: accumulation of initiators and precursors required for cell division to a respective fixed number, and (2) balanced biosynthesis: maintenance of their production proportional to volume growth. Importantly, cell division and replication initiation are independently controlled at the gene-expression level, and it is division processes - not replication initiation - that exclusively drive cell-size homeostasis in bacteria.