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It is natural to ask how bacteria coordinate metabolism when depletion of an essential nutrient limits their growth, and they must slow their entire rate of biosynthesis. A major nutrient with a fluctuating abundance is nitrogen. The growth rate of enteric bacteria under nitrogen-limiting conditions is known to correlate with the internal concentration of free glutamine, the glutamine pool. Here we compare the patterns of utilization of L-glutamine and L-glutamate, the two central intermediates of nitrogen metabolism. Monomeric precursors of all of the cells macromolecules -- proteins, nucleic acids, and surface polymers -- require the amide group of glutamine at the first dedicated step of biosynthesis. This is the case even though only a minority (~12%) of total cell nitrogen derives from glutamine. In contrast, the amino group of glutamate, which provides the remainder of cell nitrogen, is generally required late in biosynthetic pathways, e.g. in transaminase reactions for amino acid synthesis. We propose that the pattern of glutamine dependence coordinates the decrease in biosynthesis under conditions of nitrogen limitation. Hence, the glutamine pool plays a global regulatory role in the cell.
Near a bifurcation point, the response time of a system is expected to diverge due to the phenomenon of critical slowing down. We investigate critical slowing down in well-mixed stochastic models of biochemical feedback by exploiting a mapping to the
We characterize cell motion in experiments and show that the transition to collective motion in colonies of gliding bacterial cells confined to a monolayer appears through the organization of cells into larger moving clusters. Collective motion by no
The near-surface swimming patterns of bacteria are strongly determined by the hydrodynamic interactions between bacteria and the surface, which trap bacteria in smooth circular trajectories that lead to inefficient surface exploration. Here, we show
Periodic reversals of the direction of motion in systems of self-propelled rod shaped bacteria enable them to effectively resolve traffic jams formed during swarming and maximize their swarming rate. In this paper, a connection is found between a mic
We show, using differential dynamic microscopy, that the diffusivity of non-motile cells in a three-dimensional (3D) population of motile E. coli is enhanced by an amount proportional to the active cell flux. While non-motile mutants without flagella