Abstract
Cellular response to different types of stress is the hallmark of the
cell's strategy for survival. How organisms adjust their cell cycle
dynamics to compensate for changes in environmental conditions is an
important unanswered question in bacterial physiology. A cell using
binary fission for reproduction passes through three stages during its
cell cycle: a stage from cell birth to initiation of replication, a DNA
replication phase and a period of cell division. We present a detailed
analysis of durations of cell cycle phases, investigating their dynamics
under environmental stress conditions. Applying continuous steady state
cultivations (chemostats), the DNA content of a Pseudomonas putida
KT2440 population was quantified with flow cytometry at distinct growth
rates. Data-driven modeling revealed that under stress conditions, such
as oxygen deprivation, solvent exposure and decreased iron availability,
DNA replication was accelerated correlated to the severity of the
imposed stress (up to 1.9-fold). Cells maintained constant growth rates
by balancing the shortened replication phase with extended cell cycle
phases before and after replication. Transcriptome data underpin the
transcriptional upregulation of crucial genes of the replication
machinery. Hence adaption of DNA replication speed appears to be an
important strategy to withstand environmental stress.
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