Copper nanoparticles as modulator of active bacterial population and their physiology in ecosphere

The widespread use of nanoparticles (NPs) in industrial and consumer products has resulted in their emergence as significant environmental contaminants that can potentially modulate the role of bacteria in environment. This study examines the impact of different sizes of Copper nanoparticles (CuNPs) on the population and physiology of environmentally relevant gram positive (Bacillus) and gam negative (Alcaligenes, and Pseudomonas) bacteria. In general, exposure to CuNPs resulted in 4 to >6 log inactivation in bacterial population. More specifically, after 2hr exposure of Alcaligenes and Pseudomonas to 50 CuNPs, 5.75 and 6.64 log reduction noted, respectively; and their exposure to 100 CuNPs resulted in 5.97 and 6.58 log reduction, respectively. A similar exposure of laboratory and environmental isolates of Bacillus to 50 and 100 CuNPs resulted in 4.84, 4.16 and 4.35, 3.61 log reduction, correspondingly. The exposure induced elicitation of different toxicity pathways in the test bacteria. Bacterial exposure to 50 CuNPs resulted in elevated levels of LDH in Pseudomonas, in contrast these levels decreased in Alcaligenes and Bacillus. Our toxicity studies showed that exposure to CuNP can have various levels of metabolic and cellular modulation in bacterial species, suggesting that the presence of CuNPs in environment can potentially impact the pollutants-attenuation-role of bacteria in environments such as wastewater biological treatment processes.