The toxicity of two commonly used nanoparticles, silver and zinc oxide on mesophilic and halophilic bacterial cells has been investigated. Enterobacter sp., Marinobacter sp., Bacillus subtilis, halophilic bacterium sp. EMB4, were taken as model systems. The nanotoxicity was more pronounced on Gram negative bacteria. ZnO nanoparticles reduced the growth of Enterobacter sp. by 50%, while 80% reduction was observed in halophilic Marinobacter sp. In case of halophiles, this may be attributed to higher content of negatively charged cardiolipins on their cell surface. Interestingly, bulk ZnO exerted minimal reduction in growth. Ag nanoparticles were similarly cytotoxic. Nanotoxicity towards Gram positive cells was significantly less, possibly due to presence of thicker peptidoglycan layer. The bacterium nanoparticle interactions were probed by electron microscopy and energy dispersive X-ray analysis. The results indicated electrostatic interactions between nanoparticles and cell surface as the primary step towards nanotoxicity, followed by cell morphological changes, increase in membrane permeability and their accumulation in the cytoplasm.
"Although, the mechanism of antimicrobial action of MO-NPs is still not understood completely, it mainly depends on composition, surface modification and intrinsic properties of nanomaterials along with the prevalent bacterial species. NPs were found to be attached to the microbial cell with electrostatic interactions resulting in the cell wall damage along with an increase in permeability of the cell   . Pan et al. (2010), investigated the mutagenic potential of MO-NPs (Al 2 O 3 , Co 3 O 4 , CuO, TiO 2 and ZnO) and reported significant colony inhibition activity of CuO-NPs . "
[Show abstract][Hide abstract] ABSTRACT: Metal oxide nanoparticles (MO-NPs) are the multidisciplinary nano-scaled molecules which are being used
in the diagnosis and treatment of the challenging diseases including cancer. Evidence suggest that antimicrobial
formulations in the form of MO-NPs can be possibly used as effective antimicrobial agents. In addition, MO-NPs
are known to target various cellular signaling pathways associated with apoptosis, angiogenesis, metastasis and
inflammation of cancer. In combination with other chemotherapeutic/anticancer agents, MO-NPs not only
increase their bioavailability and efficacy but also lower down the requirement of active dosages. To date, to
our knowledge there is no single comprehensive report on cellular and molecular interactions of MO-NPs
which have been well elaborated in this review. Also we highlight various action mechanisms through which
MO-NPs act as antimicrobial, anticancer, antioxidant and anti-inflammatory agents.
"The toxicity of metal and metal oxidized NPs to microorganisms has been observed by others (Kumar et al. 2011a; Karn et al. 2011; Sinha et al. 2011). Moreover, Baek and An (2011) and Jiang et al. (2009) estimated the relevant free dissolved ion concentrations from the NP surfaces, including nNiO and nZnO to bacterial toxicity and found that these dissolved metal ion induced insignificant toxicity, especially in cell viability. "
[Show abstract][Hide abstract] ABSTRACT: This study investigated the cytotoxicity, genotoxicity, and growth inhibition effects of four different inorganic nanoparticles (NPs) such as aluminum (nAl), iron (nFe), nickel (nNi), and zinc (nZn) on a dibenzofuran (DF) degrading bacterium Agrobacterium sp. PH-08. NP (0-1,000 mg L(-1)) -treated bacterial cells were assessed for cytotoxicity, genotoxicity, growth and biodegradation activities at biochemical and molecular levels. In an aqueous system, the bacterial cells treated with nAl, nZn and nNi at 500 mg L(-1) showed significant reduction in cell viability (30-93.6 %, p < 0.05), while nFe had no significant inhibition on bacterial cell viability. In the presence of nAl, nZn and nNi, the cells exhibited elevated levels of reactive oxygen species (ROS), DNA damage and cell death. Furthermore, NP exposure showed significant (p < 0.05) impairment in DF and catechol biodegradation activities. The reduction in DF biodegradation was ranged about 71.7-91.6 % with single NPs treatments while reached up to 96.3 % with a mixture of NPs. Molecular and biochemical investigations also clearly revealed that NP exposure drastically affected the catechol-2,3-dioxygenase activities and its gene (c23o) expression. However, no significant inhibition was observed in nFe treatment. The bacterial extracellular polymeric materials and by-products from DF degradation can be assumed as key factors in diminishing the toxic effects of NPs, especially for nFe. This study clearly demonstrates the impact of single and mixed NPs on the microbial catabolism of xenobiotic-degrading bacteria at biochemical and molecular levels. This is the first study on estimating the impact of mixed NPs on microbial biodegradation.
"Previously Suutari and Laakso  advised caution in the strict interpretation of fatty acid signatures under conditions of stress, and this work further confirms their observations. It has been suggested that the thicker peptidoglycan layer of Gram positive species may make them less susceptible to silver toxicity , , however, our results likely reflect the situation that in contrast to other microbes, these bacteria are relatively inactive during the winter season . They could then succumb to the combination of stresses of the ‘winter to summer’ temperature transition combined with the silver treatments used here. "
[Show abstract][Hide abstract] ABSTRACT: The impact of silver nanoparticles (NPs) and microparticles (MPs) on bacterial and fungal assemblages was studied in soils collected from a low arctic site. Two different concentrations (0.066% and 6.6%) of Ag NPs and Ag MPs were tested in microcosms that were exposed to temperatures mimicking a winter to summer transition. Toxicity was monitored by differential respiration, phospholipid fatty acid analysis, polymerase chain reaction-denaturing gradient gel electrophoresis and DNA sequencing. Notwithstanding the effect of Ag MPs, nanosilver had an obvious, additional impact on the microbial community, underscoring the importance of particle size in toxicity. This impact was evidenced by levels of differential respiration in 0.066% Ag NP-treated soil that were only half that of control soils, a decrease in signature bacterial fatty acids, and changes in both richness and evenness in bacterial and fungal DNA sequence assemblages. Prominent after Ag NP-treatment were Hypocreales fungi, which increased to 70%, from only 1% of fungal sequences under control conditions. Genera within this Order known for their antioxidant properties (Cordyceps/Isaria) dominated the fungal assemblage after NP addition. In contrast, sequences attributed to the nitrogen-fixing Rhizobiales bacteria appeared vulnerable to Ag NP-mediated toxicity. This combination of physiological, biochemical and molecular studies clearly demonstrate that Ag NPs can severely disrupt the natural seasonal progression of tundra assemblages.
PLoS ONE 06/2014; 9(6):e99953. DOI:10.1371/journal.pone.0099953 · 3.23 Impact Factor
Fahimeh Abrinaei, Marzieh Shirazi, Mohammad Taghi Hosseinnejad,
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