Some bacteria, such as Bacillus subtilis, withstand starvation by forming dormant spores that revive when nutrients become available. Although sporulation and spore revival jointly determine survival in fluctuating environments, the relationship between them has been unclear. Here we show that these two processes are linked by a phenotypic “memory” that arises from a carry-over of molecules from the vegetative cell into the spore. By imaging life histories of individual B. subtilis cells using fluorescent reporters, we demonstrate that sporulation timing controls nutrient-induced spore revival. Alanine dehydrogenase contributes to spore memory and controls alanine-induced outgrowth, thereby coupling a spore’s revival capacity to the gene expression and growth history of its progenitors. A theoretical analysis, and experiments with signaling mutants exhibiting altered sporulation timing, support the hypothesis that such an intrinsically generated memory leads to a tradeoff between spore quantity and spore quality, which could drive the emergence of complex microbial traits.

Quality–quantity tradeoffs govern the production of propagules across taxa and can explain variability in life-history traits in higher organisms. A quality–quantity tradeoff was recently discovered in spore forming bacteria, but whether it impacts fitness is unclear. Here we show both theoretically and experimentally that the nutrient supply during spore revival determines the fitness advantage associated with different sporulation behaviors in Bacillus subtilis. By tuning sporulation rates we generate spore-yield and spore-quality strategists that compete with each other in a microscopic life-cycle assay. The quality (yield) strategist is favored when spore revival is triggered by poor (rich) nutrients. We also show that natural isolates from the gut and soil employ different life-cycle strategies that result from genomic variations in the number of rap-phr signaling systems. Taken together, our results suggest that a spore quality–quantity tradeoff contributes to the evolutionary adaptation of sporulating bacteria.

An industrial clavulanic acid (CA) overproducer Streptomyces clavuligerus strain, namely DEPA, was engineered to further enhance its CA production. Single or multiple copies of ccaR, claR (pathway-specific activators), and cas2 (CA synthase) genes under the control of different promoters were introduced into this strain. CA titers of the resulting recombinants were analyzed by HPLC in a dynamic fashion and compared to the vector-only controls and a wild-type strain of S. clavuligerus while their growth was monitored throughout fermentation. The addition of an extra copy of ccaR, under control of its own promoter or constitutive ermE* promoter (P ermE* ), led to 7.6-and 2.3-fold increased volumetric levels of CA in respective recombinants, namely the AK9 and ID3 strains. Its highly stable multicopy expression by the glpF promoter (P glpF ) provided up to 25.9-fold enhanced volumetric CA titers in the respective recombinant, IDG3. claR expression controlled with its own promoter or ermE* and glpF-mediated amplification in an industrial strain brought about only about 1.2-fold increase in the volumetric CA titers. An extra copy of cas2 integration with P ermE* into the S. clavuligerus DEPA genome led to 3.8-fold higher volumetric CA production by GV61. Conclusively, multicopy expression of ccaR under P glpF can result in significantly improved industrial high-titer CA producers.

This paper presents an analysis of the ability of continuum "hook" appendages to transform robot climbing.The key innovation is via exploitation of contact and impact dynamics when "grasping" the terrain. We introduce a new ellipsoid measure and use it to analyze and select the optimal shape and motion of tunable continuum hooks for given terrains and climbing scenarios. This new ellipsoid is a generalization of impact ellipsoids used previously for traditional rigid-link robots. We illustrate and support the analysis using results from laboratory experiments using a novel robot rover with continuum appendages developed by our research group.