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(Ag NP), carbon nanotubes (CNT), copper nanoparticles (CuO), iron-based
nanoparticles (Fe NP), graphene-based nanomaterials, zinc nanoparticles (ZnO),
and titanium oxide nanoparticles (TiO 2 NP), which showed nano-toxicity to microbial communities at various concentration levels (Tong et al. 2007; Johansen et al.
2008; Ge et al. 2011). The toxicity of nanoparticles also depends on the type of
microbes, for example, Gram-negative microbes reported more susceptibility due to
lesser peptidoglycan layer in the outer membrane in comparison to Gram-positive
bacteria.
In the current chapter, we review the effect of various nanoparticles on microbial
community and their enzyme activity and mechanism of nano-toxicity to microbes.
The diversified impact of nanomaterials on microbial community and their enzymatic activity still needs more research to understand the effecting concentration
threshold of nanomaterials and their role on the expression of enzymes at the community level. Further, the interaction of nanomaterials at complex microbial community is required to understand the nano-toxic effect on different parts of
biogeochemical cycles.
4.2 Nanomaterials in Environment
Nanomaterials enter in soil through the use of sewage sludge as fertilizer and spray
of nanopesticides as plant protectants (Larue et al. 2014). The use of nanoparticles
as antibacterial agent in medical industry, paint industry, food industry, catalysis,
water purification systems, and building materials increase their concentration in
environment (Aitken et al. 2006; Sharma 2009; Hossain et al. 2014). Collins et al.
(2012) studied the mobility of copper (Cu) and zinc oxide (ZnO) nanoparticles in
open pot system and reported that high organic content in soil provides the organic
coating on Cu and ZnO, which support the mobility of nanoparticles in soil. The
mobility of the nanoparticles depends on ionic strength, pH of the medium, and
organic matter. The copper nanoparticles are found least mobile in comparison to
copper oxide, iron oxide, titanium oxide, and zinc oxide nanoparticles. The dissolution and transformation of nanoparticles are also obtained with time in environment
which affect the concentration of nanoparticles.
Nanoparticles interact with dissolved organic matter, multivariate cations or
anions and natural colloids, which affect the stability of nanoparticles and their
aging process. The coating of nanoparticles also plays a significant role in their
stability, which decides the interaction of nanoparticles with the surrounding environment and their aggregation. Erhayem and Sohn (2014) found that adsorption
constants of organic material to titanium oxide nanoparticles decreased in the order
humic acid (HA) > natural organic matter > fulvic acid (FA), which showed with
different degrees of stabilization. Tween 80-coated silver nanoparticles showed
more stability in comparison to citrate-coated silver nanoparticles in freshwater
medium, but still there are no specific determinants that can predict which conditions like coating, natural organic matter, surrounding cations, pH, engineered
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…
(Ag NP), carbon nanotubes (CNT), copper nanoparticles (CuO), iron-based
nanoparticles (Fe NP), graphene-based nanomaterials, zinc nanoparticles (ZnO),
and titanium oxide nanoparticles (TiO 2 NP), which showed nano-toxicity to microbial communities at various concentration levels (Tong et al. 2007; Johansen et al.
2008; Ge et al. 2011). The toxicity of nanoparticles also depends on the type of
microbes, for example, Gram-negative microbes reported more susceptibility due to
lesser peptidoglycan layer in the outer membrane in comparison to Gram-positive
bacteria.
In the current chapter, we review the effect of various nanoparticles on microbial
community and their enzyme activity and mechanism of nano-toxicity to microbes.
The diversified impact of nanomaterials on microbial community and their enzymatic activity still needs more research to understand the effecting concentration
threshold of nanomaterials and their role on the expression of enzymes at the community level. Further, the interaction of nanomaterials at complex microbial community is required to understand the nano-toxic effect on different parts of
biogeochemical cycles.
4.2 Nanomaterials in Environment
Nanomaterials enter in soil through the use of sewage sludge as fertilizer and spray
of nanopesticides as plant protectants (Larue et al. 2014). The use of nanoparticles
as antibacterial agent in medical industry, paint industry, food industry, catalysis,
water purification systems, and building materials increase their concentration in
environment (Aitken et al. 2006; Sharma 2009; Hossain et al. 2014). Collins et al.
(2012) studied the mobility of copper (Cu) and zinc oxide (ZnO) nanoparticles in
open pot system and reported that high organic content in soil provides the organic
coating on Cu and ZnO, which support the mobility of nanoparticles in soil. The
mobility of the nanoparticles depends on ionic strength, pH of the medium, and
organic matter. The copper nanoparticles are found least mobile in comparison to
copper oxide, iron oxide, titanium oxide, and zinc oxide nanoparticles. The dissolution and transformation of nanoparticles are also obtained with time in environment
which affect the concentration of nanoparticles.
Nanoparticles interact with dissolved organic matter, multivariate cations or
anions and natural colloids, which affect the stability of nanoparticles and their
aging process. The coating of nanoparticles also plays a significant role in their
stability, which decides the interaction of nanoparticles with the surrounding environment and their aggregation. Erhayem and Sohn (2014) found that adsorption
constants of organic material to titanium oxide nanoparticles decreased in the order
humic acid (HA) > natural organic matter > fulvic acid (FA), which showed with
different degrees of stabilization. Tween 80-coated silver nanoparticles showed
more stability in comparison to citrate-coated silver nanoparticles in freshwater
medium, but still there are no specific determinants that can predict which conditions like coating, natural organic matter, surrounding cations, pH, engineered
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…