Stress Response-Based Whole-Cell Biosensor Development: Sentinels, Serendipity, and Circuitry

Abstract

By 1970, perhaps the two outstanding examples of global control of gene expression had been described in Escherichia coli, namely, stringent control of ribosome biogenesis and activation of alternative catabolic operons upon glucose exhaustion. In the ensuing decades, a large number of analogous global regulatory circuits were discovered using ever more sophisticated biochemical and genetic techniques. These global regulatory systems included those activated by stresses, be they chemical, physical, biological, or nutritional. Such stress responses serve an adaptive function allowing cells to readjust in a battle to thrive. Thus these responses, often transcriptional, generally are triggered at sublethal levels by still metabolically active cells. In the early 1990s, facile monitoring of stress response induction using easily measured reporter gene products was exploited as early warning systems for a wide range of environmental and toxicological applications. The development of this whole-cell biosensor concept is recounted within the context of interacting societal, economic, and fundamental scientific concerns as well as prior research efforts.

Graphical Abstract