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.
"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
"Extensive studies were carried out to assess the antibacterial effects of metal oxide and polymeric NPs (Auffan et al. 2009; Chapman et al. 2010; Anselme et al. 2010). Most of these studies focused on killing or growth inhibition of planktonic cells (Choi et al. 2008; Ruparelia et al. 2008; Sinha et al. 2011; Zhang et al. 2010). Investigations are limited in the assessment of toxicity of NPs to bacterial cells. "
[Show abstract][Hide abstract] ABSTRACT: Understanding the mechanism of nanoparticle (NP) induced toxicity in microbes is of
potential importance to a variety of disciplines
including disease diagnostics, biomedical implants,
and environmental analysis. In this context, toxicity to
bacterial cells and inhibition of bioﬁlm formation by
GaN NPs and their functional derivatives have been
investigated against gram positive and gram negative
bacterial species down to single cellular level. High
levels of inhibition of bioﬁlm formation ([80 %) was
observed on treatments with GaN NPs at sub-micro
molar concentrations. These results were substantiated
with morphological features investigated with ﬁeld
emission scanning electron microscope, and the
observed changes in vibrational modes of microbial
cells using Raman spectroscopy. Raman spectra
provided molecular interpretation of cell damage by
registering signatures of molecular vibrations of
individual living microbial cells and mapping the
interplay of proteins at the cell membrane. As
compared to the untreated cells, Raman spectra of
NP-treated cells showed an increase in the intensities
of characteristic protein bands, which conﬁrmed
membrane damage and subsequent release of cellular
contents outside the cells. Raman spectral mapping at
single cellular level can facilitate understanding of the
mechanistic aspect of toxicity of GaN NPs. The effect
may be correlated to passive diffusion causing
mechanical damage to the membrane or ingress of
(ionic radius*0.076 nm) which can potentially
interfere with bacterial metabolism, as it resembles
(ionic radius*0.077 nm), which is essential for
Journal of Nanoparticle Research 07/2013; 15(8):1841. DOI:10.1007/s11051-013-1841-9 · 2.18 Impact Factor
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