Our understanding of bacterial cell size control is based mainly on stress-free growth conditions in the laboratory [1–10]. In the real world, however, bacteria are routinely faced with stresses that produce long filamentous cell morphologies [11–28]. Escherichia coli is observed to filament in response to DNA damage [22–25], antibiotic treatment [11–14, 28], host immune systems [15, 16], temperature [17], starvation [20], and more [18, 19, 21], conditions which are relevant to clinical settings and food preservation [26]. This shape plasticity is considered a survival strategy [27]. Size control in this regime remains largely unexplored. Here we report that E. coli cells use a dynamic size ruler to determine division locations combined with an adder-like mechanism to trigger divisions. As filamentous cells increase in size due to growth, or decrease in size due to divisions, its multiple Fts division rings abruptly reorganize to remain one characteristic cell length away from the cell pole and two such length units away from each other. These rules can be explained by spatiotemporal oscillations of Min proteins. Upon removal of filamentation stress, the cells undergo a sequence of division events, randomly at one of the possible division sites, on average after the time required to grow one characteristic cell size. These results indicate that E. coli cells continuously keep track of absolute length to control size, suggest a wider relevance for the adder principle beyond the control of normally sized cells, and provide a new perspective on the function of the Fts and Min systems. Wehrens, Ershov, et al. report a new size-control mechanism in E. coli cells that have elongated due to stress. Multiple division rings are continuously rearranged in response to growth and division to control daughter cell size when divisions resume. Divisions are spatially controlled by the Min system and temporally by the adder principle.

Microorganisms have developed an elaborate spectrum of mechanisms to respond and adapt to environmental stress conditions. Among these is the expression of dps, coding for the DNA-binding protein from starved cells. Dps becomes the dominant nucleoid- organizing protein in stationary-phase Escherichia coli cells and is required for robust survival under stress conditions, including carbon or nitrogen starvation, oxidative stress, metal exposure, and irradiation. To study the complex regulation of Dps in E. coli, we utilized time-lapse fluorescence microscopy imaging to examine the kinetics, input encoding, and variability of the Dps response in single cells. In the presence of an oxidative stressor, we observed a single pulse of activation of Dps production. Increased concentrations of H₂O₂ led to increased intensity and duration of the pulse. While lower concentrations of H₂O₂ robustly activated the Dps response with little effect on the growth rate, higher concentrations of H₂O₂ resulted in dramatically lower and highly varied growth rates. A comparison of cells exposed to the same concentration of H₂O₂ revealed that increased levels of Dps expression did not confer a growth advantage, indicating that recovery from stress may rely primarily upon variation in the amount of damage caused to individual cells.

To understand droplet formation and stabilisation, technologies are needed to measure interfacial tension at micrometer range and millisecond scale. In this paper, microtechnology is used, and that allows us to access these ranges and derive a model for surfactant free systems. The predicting power of the model was tested, and we found that it can be used to accurately (validated with >60 experiments) describe droplet size for a wide range of flow rates, interfacial tensions, and continuous phase viscosities.The model was used next to determine interfacial tensions in a system with hexadecane and sodium dodecylsulfate (SDS) solutions, and it was found that the model can be used for droplet formation times ranging from 0.4 to 9.4 ms while using a wide range of process conditions.The method described here differs greatly from standard dynamic interfacial tension methods that use quiescent, mostly diffusion-limited situations. The effects that we measured are much faster due to enhanced mass transfer; this allows us to assess the typical time scales used in industrial emulsification devices.