Two-component system cross-regulation integrates Bacillus anthracis response to heme and cell envelope stress.

Two-component signaling systems (TCSs) are one of the mechanisms that bacteria employ to sense and adapt to changes in the environment. A prototypical TCS functions as a phosphorelay from a membrane-bound sensor histidine kinase (HK) to a cytoplasmic response regulator (RR) that controls target gene expression. Despite significant homology in the signaling domains of HKs and RRs, TCSs are thought to typically function as linear systems with little to no cross-talk between non-cognate HK-RR pairs.

Look and see if it is time to induce protein expression in Escherichia coli cultures.

It is shown that Methyl Red can be used as an indicator dye that changes color in Escherichia coli culture as a result of time- and cell density-dependent bleaching by azoreductase produced by the bacteria. For cell cultures that are being used to express a recombinant protein, this phenomenon can be exploited to provide a simple visual cue that cell cultures have reached an appropriate growth phase for addition of an agent to induce protein expression, such as isopropyl thiogalactoside.