No abstract

Bacteria use two-component system (TCS) signaling pathways to sense and respond to peptides involved in host defense, quorum sensing, and inter-bacterial warfare. However, little is known about the peptide-sensing capabilities of these TCSs. Here, we develop a high-throughput E. coli display method to characterize the effects of human antimicrobial peptides (AMPs) on the pathogenesis-regulating TCS PhoPQ of Salmonella Typhimurium. We find that PhoPQ senses AMPs comprising diverse sequences, structures, and biological functions. Using thousands of AMP variants, we identify sub-domains and biophysical features responsible for PhoPQ activation. We show that most of the newfound activators induce PhoPQ in S. Typhimurium, suggesting a role in virulence regulation. Finally, we find that PhoPQ homologs from Klebsiella pneumoniae and extraintestinal pathogenic E. coli, which occupy different in vivo niches, exhibit distinct AMP response profiles. Our high-throughput method enables new insights into the specificities, mechanisms, and evolutionary dynamics of TCS-mediated peptide sensing in bacteria.

Flavonoids are important value added products for dye sensitized solar cells biosensors, functional foods, medicinal supplements, nanomaterial synthesis, and other applications. Brassica oleracea contains high levels of anthocyanins in leaf sap vacuoles, and there are many viable extraction techniques that vary in terms of simplicity, environmental impact, cost, and extract photochemical/electrochemical properties. The efficiency of value added biotechnologies from flavonoid is a function of anthocyanin activity/concentration and molecule stability (i.e., ability to retain molecular resonance under a wide range of conditions). In this paper, we show that block cryoconcentration and partial thawing of anthocyanin from B. oleracea is a green, facile, and highly efficient technique that does not require any special equipment or protocols for producing enhanced value added products. Cryoconcentration increased anthocyanin activity and total phenol content approximately 10 times compared with common extraction techniques. Cryoconcentrated extract had enhanced electrochemical properties (higher oxidation potential), improved chroma, and higher UV absorbance than extract produced with other methods for a pH range of 2-12, with minimal effect on the diffusion coefficient of the extract. As a proof of concept for energy harvesting and sensor applications, dye sensitized solar cells and pH-sensitive thin films were prepared and tested. These devices were comparable with other recently published biotechnologies in terms of efficacy, but did not require expensive/environmentally detrimental extraction or concentration methods. This low cost, biorenewable, and simple method can be used for development of a variety of value added products. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:206-217, 2018.