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Maximizing protein secretion is an important target in the design of engineered living systems. In this paper, we characterize a tradeoff between cell growth and per cell protein secretion in the curli biofilm secretion system of E Coli Nissile 1917. Initial characterization using 24-hour 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 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 accumulation of protein containing the outer membrane transport tag in the periplasmic space. RNA sequencing experiments indicate upregulation of known periplasmic stress response genes in the highly secreting variant, further implicating periplasmic stress in the growth-secretion tradeoff. Overall, these results motivate additional strategies for optimizing total protein production and longevity of secretory engineered living systems.

© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Li 3 BN 2 is investigated for the first time as a transition metal free, high capacity cathode material for Li-ion batteries. It is shown that α-Li 3 BN 2 can exhibit a specific capacity of 890 mA h g −1 with the charge storage mechanism associated with the valence state change of N ions in the BN 2 anion. The specific capacity demonstrated in this study is the highest one ever reported in literature for an intercalation-type cathode material. Further, using the valence state change of N ions as a charge storage mechanism opens the door for designing additional high performance, transition metal free electrodes in the future.

We have integrated a biomarker detection system with a rover for the search for sparse life in extreme environments. The system incorporated a pulsed fluorescence imager, a reagent sprayer, and a surface scraping device for remote detection of fluorescence signals.

We deployed our fluorescence imaging system which detects fluorescence signals from sparse microorganisms and biofilms on Carnegie Mellon University’s autonomous rover Zoë. The results of the 2004 Atacama Desert field season, in Chile, are discussed.