Periplasmic stress contributes to a trade-off between protein secretion and cell growth in Escherichia coli Nissle 1917.

Maximizing protein secretion is an important target in the design of engineered living systems. In this paper, we characterize a trade-off between cell growth and per-cell protein secretion in the curli biofilm secretion system of Escherichia coli Nissle 1917. Initial characterization using 24-h continuous growth and protein production monitoring confirms decreased growth rates at high induction, leading to a local maximum in total protein production at intermediate induction. Propidium iodide (PI) staining at the endpoint indicates that cellular death is a dominant cause of growth reduction. Assaying variants with combinatorial constructs of inner and outer membrane secretion tags, we find that diminished growth at high production is specific to secretory variants associated with periplasmic stress mediated by outer membrane secretion and periplasmic accumulation of protein containing the outer membrane transport tag. RNA sequencing experiments indicate upregulation of known periplasmic stress response genes in the highly secreting variant, further implicating periplasmic stress in the growth-secretion trade-off. Overall, these results motivate additional strategies for optimizing total protein production and longevity of secretory engineered living systems Graphical Abstract.

Simulation training improves team dynamics and performance in a low-resource cardiac intensive care unit.

INTRODUCTION: Although simulation training has been utilized quite extensively in highincome medical environments, its feasibility and effect on team performance in lowresource pediatric Cardiac Intensive Care Unit (CICU) environments has not been demonstrated. We hypothesized that lowfidelity simulationbased crisis resource management training would lead to improvements in team performance in such settings. METHODS: In this prospective observational study, the effect of simulation on team dynamics and performance was assessed in 23 healthcare providers in a pediatric CICU in Southeast Asia. A 5day training program was utilized consisting of various didactic sessions and simulation training exercises. Improvements in team dynamics were assessed using participant questionnaires, expert evaluations, and video analysis of time to intervention and frequency of closedloop communication. RESULTS: In subjective questionnaires, participants noted significant (P < 0.05) improvement in team dynamics and performance over the training period. Video analysis revealed a decrease in time to intervention and significant (P < 0.05) increase in frequency of closedloop communication because of simulation training. CONCLUSIONS: This study demonstrates the feasibility and effectiveness of simulationbased training in improving team dynamics and performance in lowresource pediatric CICU environments, indicating its potential role in eliminating communication barriers in these settings.