Changes in microbiological metabolism under chemical stress

Chemical stress may alter microbiological metabolism and this, in turn, may affect the natural and engineered systems where these organisms function. The impact of chemical stress on microbiological metabolism was investigated using model chemicals 2,4-dinitrophenol (DNP), pentachlorophenol (PCP), and N-ethylmaleimide (NEM). Biological activity of Pseudomonas aeruginosa was measured in batch systems, with and without stressors at sub-lethal concentrations. Stressor DNP, between 49 and 140 mg l^-1, and PCP, at 15 and 38 mg l^-1, caused decreases in biomass growth yields, but did not inhibit substrate utilization rates. These effects increased with stressor concentrations, showing as much as a 10% yield reduction at the highest DNP concentration. This suggests that a portion of carbon and energy resources are diverted from growth and used in stress management and protection. Stressor DNP, between 300 and 700 mg l^-1, and PCP at 85 mg l^-1 caused decreases in growth yields and substrate utilization rates. This suggests an inhibition of both anabolism and catabolism. Stressor NEM was the most potent, inhibiting biological activity at concentrations as low as 2.7 mg l^-1. These findings will ultimately be useful in better monitoring and management of biological treatment operations and contaminated natural systems.