Impacts of tetracycline on planktonic bacterial production in prairie aquatic systems.

In view of antibiotics being detected in surface waters, experiments were conducted to determine the impacts of tetracycline on planktonic bacteria in wetland and river waters. The minimum inhibitory concentration (MIC) method is often used to measure for resistance or susceptibility of microbes to antibiotics with typical concentrations of antibiotics being mg L(-1). Moreover, there is the belief that antibiotics in the lower microg L(-1) range are unlikely to affect bacteria. We examined this assumption by measuring the effects of a broad range of tetracycline concentrations on bacterial protein production by the incorporation of L-[4,5-3H]leucine method. Tetracycline significantly (P < 0.05) inhibited production in river water bacteria at a "free" concentration of 5 microg L(-1), but the inhibition was significant only at 1000 microg L(-1) in wetland water. The data indicate that planktonic bacteria can be very sensitive to tetracycline at extremely low concentrations and that microbial production is seriously affected.