Abstract
Hormesis has aroused much attention during the past two decades and may have great implications on many fields, including toxicology and risk assessment. However, the observation of hormesis remains challenged under laboratory conditions. To determine favorable conditions under which to observe hormesis, we investigated the hormetic responses of Escherichia coli (E. coli) upon exposure of different concentrations of sulfonamides and erythromycin at different time points and in different culture media: Luria-Bertani (LB) broth and Mueller Hinton (MH) broth. Our results reveal that the antibiotics, both individually and combined, produce hormetic effects on E. coli growth in MH broth at the stationary phase, with the maximum stimulatory response increasing with time. However, in LB broth, the hormetic response was not observed, which can be explained by an analogous “wood barrel theory”. Our study suggests that the culture medium and time should be taken into consideration in hormetic studies, and compound mixtures should also receive more attention for their potential to induce hormesis.
Highlights
The dose-response relationship is the most fundamental concept in toxicology, and environmental risk assessment is conducted based on this relationship [1]
The E. coli growth curves were investigated in different concentrations of LB and Mueller Hinton (MH) broth media
E. coli in LB broth showed a shorter lag time, a faster growth rate and a greater maximum achieved OD600 than those in the MH media
Summary
The dose-response relationship is the most fundamental concept in toxicology, and environmental risk assessment is conducted based on this relationship [1]. The two traditional models have been challenged with an alternative model that has aroused many concerns over the past two decades [3]. This dose-response model is defined as hormesis, which refers to a biphasic dose-response relationship with low dose stimulation and high dose inhibition [4]. Studies [5,6] have indicated that hormesis can better predict low-dose responses, and the hormetic dose-response model is more common than the threshold model in toxicology. Calabrese [7] has argued that
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