Copper nanoparticles toxicity: Laboratory strains verses environmental bacterial isolates

Transcriptome Analysis Reveals the Growth Promotion Mechanism of Enteropathogenic Escherichia coli Induced by Black Phosphorus Nanosheets

With the extensive production and application of black phosphorus (BP) nanosheets, release to the environment is inevitable, which raises concerns about the fate and effects of this two-dimensional (2D) material on sensitive receptors such as environmental microbes. Although the bacterial toxicity of BP nanosheets has been demonstrated, whether the biological response differs in pathogenic and nonpathogenic strains of a microorganism is unknown. Here, enteropathogenic Escherichia coli (EPEC) and nonpathogenic Escherichia coli DH5α (E. coli DH5α), Escherichia coli k12 (E. coli k12), and Bacillus tropicus (B. tropicus) are used to comparatively study the microbial toxicity of BP nanosheets. Upon exposure to BP nanosheets across a range of doses from 10 to 100 μg mL^-1 for 12 h, EPEC experienced enhanced growth and E. coli DH5α and E. coli k12 were not affected, whereas B. tropicus exhibited clear toxicity. By combining transcriptome sequencing, proteome analysis, and other sensitive biological techniques, the mechanism of BP-induced growth promotion for EPEC was uncovered. Briefly, BP nanosheets activate the antioxidation system to resist oxidative stress, promote protein synthesis and secretion to attenuate membrane damage, enhance the energy supply, and activate growth-related pathways. None of these impacts were evident with nonpathogenic strains. By describing the mechanism of strain-dependent microbial effects, this study not only highlights the potential risks of BP nanosheets to the environment and to human health but also calls attention to the importance of model strain selection when evaluating the hazard and toxicity of emerging nanomaterials.

Autophagy and apoptosis mediated nano-copper-induced testicular damage

Nano-copper has been increasingly employed in various products. In previous studies, we showed that nano-copper caused damage in the rat testis, but it remains unclear whether the toxic reaction can affect the reproductive function. In this study, following 28 d of exposure to nano-copper at a dose of 44, 88, and 175 mg/kg/day, there was a decrease in sperm quality, fructose content, and the secretion of sex hormones. Nano-copper also increased the level of oxidative stress, sperm malformation rate, and induced abnormal structural changes in testicular tissue. Moreover, Nano-copper upregulated the expression of apoptosis-related protein Bax and autophagy-related protein Beclin, and downregulated the expression of Bcl2 and p62. Furthermore, nano-copper (175 mg/kg) downregulated the protein expression of AMPK, p-AKT, mTOR, p-mTOR, p-4E-BP1, p70S6K, and p-p70S6K, and upregulated the protein expression of p-AMPK. Therefore, nano-copper induced damage in testicular tissues and spermatogenesis is highly related to cell apoptosis and autophagy by regulating the Akt/mTOR signaling pathway. In summary, excess exposure to nano-copper may induce testicular apoptosis and autophagy through AKT/mTOR signaling pathways, and damage the reproductive system in adult males, which is associated with oxidative stress in the testes.

Anaerobic fermentation metabolism of Moorella thermoacetica inhibited by copper nanoparticles: Comprehensive analyses of transcriptional response and enzyme activity

Engineered nanoparticles are observed to be released into the environment and ended up in wastewater treatment plants. It has been reported that these nanoparticles in sewage might have a toxic effect on microorganisms, and thus affect anaerobic microbial fermentation. However, the mechanisms involved in nanoparticles-induced effects on the anaerobic acidification process and its related bacterial metabolism are still unclear. This work indicated that copper nanoparticles (Cu NPs) were able to cause cell membrane oxidative damage and inhibit the growth and metabolism of Moorella thermoacetica (a model acetogen). The OD₆₀₀ and acetic acid production of M. thermoacetica in the presence of 1 mg/L of Cu NPs were decreased to 29.2% and 40.7% of the control, respectively. The key mechanism of the inhibitory effect was governed by the fact that Cu NPs significantly reduced the glucose consumption, and led to the decreased pyruvate metabolism levels. Additionally, Cu NPs inhibited the gene expressions and catalytic activities of the key enzymes related to acetic acid production. It was identified that the relative activities of phosphofructokinase, pyruvate kinase, phosphotransacetylase, and acetate kinase of M. thermoacetica in the presence of 1 mg/L of Cu NPs decreased to only 70.1%, 69.3%, 50.1%, and 65.2% of the control, respectively. These results demonstrated that the release of Cu NPs in the environment could pose risks to anaerobic fermentation processes via regulating microbial transcriptional response and enzyme activity.