Toxicity of metallic nanoparticles in microorganisms- A review

Recent advances in the synthesis and development of nanoparticles (NPs) for wide applications has lead to a serious threat to both human and environmental health. NPs are highly reactive and catalytic in nature compared to their ions or bulk counterparts and thus applicable in various fields including drug delivery, electronics, optics, and therapeutics. Due to these applications, many varieties of NPs in massive amounts are being industrially produced. These NPs are discharged in to the environment and thus providing a path to enter into food chain via microorganisms and eventually disturbs the ecological balance. The NPs exhibit toxicity to living organisms mainly because of their small size (>100∈nm), large surface-to-volume ratio and highly reactive facets. The microorganisms including bacteria present in the natural ecosystem are the primary targets that get exposed to NPs. Before these NPs enter into the food chain, it is imperative to evaluate the toxicity associated with NPs in microorganisms. The most convenient and rapid way is to perform toxicity analysis using microorganisms such as bacteria. Toxicity of nanomaterials using microorganisms such as E.coli, Pseudomonas, Bacillus as models for prokaryotes gives an insight into the toxic impacts of NPs. Toxicities associated with NPs in microorganisms is mainly related to their nano-size that cause membrane disorganization, generation of reactive oxygen species (ROS) and in some ases, oxidative DNA damage. In this review article we describe the toxicity of various nanoparticles in bacteria and provide a rationale for assessing nanotoxicity and discuss the current status on toxicity impacts on microorganisms.