111
concentration (1000 mg.kg
−1
) it reduced Waddlia, Holophaga, Derxia, and Opitutus
bacterial species but increased Cellulomonas, Rhodococcus, Pseudomonas, and
Nocardioides bacterial community (Shrestha et al. 2013).
4.5.3 Copper Oxide Nanoparticles
Copper oxide nanoparticles also affected microbial community with their presence.
Gajjar et al. (2009) reported that copper oxide generates free radicals which create
toxicity toward bacteria. Similarly, Rousk et al. (2012) also found decay in bacterial
growth in mineral soil by copper oxide nanoparticles. Further, Xu et al. (2015) evaluated the impact of copper nanoparticles on soil microbial community at concentration 100–1000 mg.kg
−1
in flooded paddy soil. They measured negative impact on
soil microbial biomass, total phospholipid fatty acid, urease, phosphates, and dehydroxygenase enzyme activity. Recently, Simonin et al. (2018) reported that copper
oxide nanoparticles negatively affected microbial activity related to nitrogen and
carbon cycles in soil. These nanoparticles significantly affected denitrification,
nitrification, and soil respiration activities in soil microbes at 100 mg/kg concentration. Further, Jośko et al. (2019) found that exposure of copper and zinc nanoparticles in soil for 730 days did not cause significant change in microbial activity at
10 mg.kg
−1
concentration. They reported that decrease in zinc and copper concentration with time does not mean reduction in their toxicity, but it depends on the type
of species in microbial community and their tolerance capacity and adaptation to
present engineered nanomaterial in the surrounding environment.
4.5.4 Titanium Oxide Nanoparticles
Titanium dioxide nanoparticles (nano-TiO 2 ) are the most applicable nanoparticles
in personal care industry, food industry as additive, in solar cell as photocatalyst and
pigment industry (Tan et al. 2018). The wide use of titanium oxide nanoparticles led
their distribution in different environmental sector and their impact on microbial
community. It has been reported that TiO 2 nanoparticles retained in soil system for
long period and interacted with plants and microbial system (Du et al. 2011). Fang
et al. (2010) reported that titanium oxide nanoparticle increased cell permeability
by damaging cell membrane of Nitrosomonas europaea. In addition to the bacterial
community titanium oxide nanoparticles significantly affected the arbuscular
mycorrhizal fungal community in soil (Burke et al. 2014).
Titanium oxide nanoparticles showed both positive and negative impact on soil
microbial community by reducing and scaling up the microbial diversity (Ge et al.
2011; Shah et al. (2014). Du et al. (2011) found negative impact of titanium oxide
nanoparticles in soil enzyme activity. They measured decrease in soil protease,
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…
concentration (1000 mg.kg
−1
) it reduced Waddlia, Holophaga, Derxia, and Opitutus
bacterial species but increased Cellulomonas, Rhodococcus, Pseudomonas, and
Nocardioides bacterial community (Shrestha et al. 2013).
4.5.3 Copper Oxide Nanoparticles
Copper oxide nanoparticles also affected microbial community with their presence.
Gajjar et al. (2009) reported that copper oxide generates free radicals which create
toxicity toward bacteria. Similarly, Rousk et al. (2012) also found decay in bacterial
growth in mineral soil by copper oxide nanoparticles. Further, Xu et al. (2015) evaluated the impact of copper nanoparticles on soil microbial community at concentration 100–1000 mg.kg
−1
in flooded paddy soil. They measured negative impact on
soil microbial biomass, total phospholipid fatty acid, urease, phosphates, and dehydroxygenase enzyme activity. Recently, Simonin et al. (2018) reported that copper
oxide nanoparticles negatively affected microbial activity related to nitrogen and
carbon cycles in soil. These nanoparticles significantly affected denitrification,
nitrification, and soil respiration activities in soil microbes at 100 mg/kg concentration. Further, Jośko et al. (2019) found that exposure of copper and zinc nanoparticles in soil for 730 days did not cause significant change in microbial activity at
10 mg.kg
−1
concentration. They reported that decrease in zinc and copper concentration with time does not mean reduction in their toxicity, but it depends on the type
of species in microbial community and their tolerance capacity and adaptation to
present engineered nanomaterial in the surrounding environment.
4.5.4 Titanium Oxide Nanoparticles
Titanium dioxide nanoparticles (nano-TiO 2 ) are the most applicable nanoparticles
in personal care industry, food industry as additive, in solar cell as photocatalyst and
pigment industry (Tan et al. 2018). The wide use of titanium oxide nanoparticles led
their distribution in different environmental sector and their impact on microbial
community. It has been reported that TiO 2 nanoparticles retained in soil system for
long period and interacted with plants and microbial system (Du et al. 2011). Fang
et al. (2010) reported that titanium oxide nanoparticle increased cell permeability
by damaging cell membrane of Nitrosomonas europaea. In addition to the bacterial
community titanium oxide nanoparticles significantly affected the arbuscular
mycorrhizal fungal community in soil (Burke et al. 2014).
Titanium oxide nanoparticles showed both positive and negative impact on soil
microbial community by reducing and scaling up the microbial diversity (Ge et al.
2011; Shah et al. (2014). Du et al. (2011) found negative impact of titanium oxide
nanoparticles in soil enzyme activity. They measured decrease in soil protease,
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…