Adaptations in microbiological populations exposed to dinitrophenol and other chemical stressors

Microbiological populations in natural and engineered systems may experience multiple exposures to chemical stressors, which may affect system functions. The impact of such exposures on the metabolism of a population of Pseudomonas aeruginosa was studied using respirometry. Two serial exposures to low concentrations of 2,4-dinitrophenol (DNP), pentachlorophenol (PCP), or N-ethyl maleimide (NEM) did not affect metabolism beyond that expected for a single exposure. However, at higher concentrations, three exposures to DNP led to a combination of metabolic stress and resilience in the population. At a low DNP concentration of 400 mg/L, multiple exposures led to increased stress but indicated no development of resilience. At a high DNP concentration of 1,200 mg/L, no biological activity was observed, indicating that the population did not survive the exposure. At intermediate concentrations of 800 and 900 mg/L DNP, stress was observed, but it was found to decrease after multiple exposures. This, combined with the observation that the size of the population decreased, indicated that resilience in the population had developed because of elimination of the weaker organisms in the population. In contrast, the lack of resilience at the lower DNP concentration was attributed to the survival of the strong as well as weak members, lowering the resilience of the population as a whole. The development of resilience within a window of stressor concentrations is an important finding with implications for predicting the performance of biotreatment processes and biosensor technologies and for interpreting ecotoxicity risk assessments.