Fig. 1.

Potential impact of changes in MTA concentrations on an infection. This figure imagines the path that a Salmonella-infected host might take through health-by-microbe phase space (1). The host starts in the upper left corner, the microbes grow, the individual sickens, and then, the microbes are cleared; the host recovers, producing a looping resilient curve. Using the conditions suggested in the work by Ko et al. (2), a constitutively high MTA level might result in an increased ability to clear the microbes at a cost of increased damage. These hosts would have low infection tolerance. Under starvation conditions, the host might clear the pathogens less well but would be more tolerant, because it would take more microbes to cause damage. If MTA levels change dynamically, they could tune the phase curve to minimize both microbe load and damage.