107
zinc oxide, and titanium oxide at 1 mg concentration showed both positive and
negative response on microbial community. It was observed that zinc oxide and
cerium oxide reduced the abundance of potassium and phosphorus reduction bacteria and hindered their enzymatic activity and silicon oxide increased their activity
(Chai et al. 2015).
The carbon nanomaterial did not affect soil microbial activity at short-term
experiment but changed C-14 glucose incorporation into bacterial biomass at
1–1000 mg.kg-1 concentration (Oyelami and Semple 2015). Recently, Ge et al.
(2018) studied the effect of carbon nanomaterial on soil microbial community and
observed the alternation of microbial community composition related to carbon (C),
nitrogen (N), and sulfur (S) biological cycles.
Chen et al. (2017) found low toxicity of silver, zinc, and titanium nanoparticles
to soil microbial community and measured abundance in Gram-negative and anaerobic bacteria at low concentration of engineered nanoparticle (ENP). Similarly,
Simonin et al. (2017) also found the toxic effect of titanium oxide on ammoniaoxidizing archaea and bacteria, Nitrobacter and Nitrospira, which play a significant
role in nitrite oxidation. They found about 40% reduction in ammonia-oxidizing
archaea, Nitrobacter and ammonia-oxidizing bacteria after 90 days of exposure at
<1 mg.kg
−1
concentration.
Nature of metal in nanoparticle also affects the microbial community at the same
concentration level. Asadishad et al. (2018) studied the effect of silver, copper
oxide, zinc oxide, and titanium oxide at 1–100 mg.kg
−1
concentration on microbial
community and enzyme activity and found that after 30 days of exposure zinc oxide
and copper oxide did not affect or increase the soil enzyme activity but in contrast,
silver inhibited enzyme activity at high concentration, while titanium oxide did not
change significantly. Cao et al. (2017) found that silver nanoparticles influenced
mycorrhizal community in maize plant at 2.5 mg.kg
−1
concentration. They reported
that anti-oxidation activity of silver decreases diversity of mycorrhizal fungi,
resulted in decrease in colonization rate of root mycorrhizal fungi, reduction in soil
alkaline phosphatase activity and available phosphorus content to maize plant.
Silver nanoparticles also decrease the mutualistic relation of mycorrhizal fungi and
maize plant, which influenced the soil phosphoric cycle and affect soil fertility.
4.5 Effect on Microbial Community Structure
and Enzymatic Activities
The microbial community structure is majorly affected by the surrounding environment. Presence of metal nanomaterials in their surrounding directly interacted with
microbes and regulate their physiology by positive or negative route. Concentration
of nanoparticle is the most important factor, which plays a significant role in growth
or inhibition of microbial population and their enzymatic profiles. Different types of
enzymatic activity such as soil protease, dehydrogenase, urease, nitrogen fixation,
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…
zinc oxide, and titanium oxide at 1 mg concentration showed both positive and
negative response on microbial community. It was observed that zinc oxide and
cerium oxide reduced the abundance of potassium and phosphorus reduction bacteria and hindered their enzymatic activity and silicon oxide increased their activity
(Chai et al. 2015).
The carbon nanomaterial did not affect soil microbial activity at short-term
experiment but changed C-14 glucose incorporation into bacterial biomass at
1–1000 mg.kg-1 concentration (Oyelami and Semple 2015). Recently, Ge et al.
(2018) studied the effect of carbon nanomaterial on soil microbial community and
observed the alternation of microbial community composition related to carbon (C),
nitrogen (N), and sulfur (S) biological cycles.
Chen et al. (2017) found low toxicity of silver, zinc, and titanium nanoparticles
to soil microbial community and measured abundance in Gram-negative and anaerobic bacteria at low concentration of engineered nanoparticle (ENP). Similarly,
Simonin et al. (2017) also found the toxic effect of titanium oxide on ammoniaoxidizing archaea and bacteria, Nitrobacter and Nitrospira, which play a significant
role in nitrite oxidation. They found about 40% reduction in ammonia-oxidizing
archaea, Nitrobacter and ammonia-oxidizing bacteria after 90 days of exposure at
<1 mg.kg
−1
concentration.
Nature of metal in nanoparticle also affects the microbial community at the same
concentration level. Asadishad et al. (2018) studied the effect of silver, copper
oxide, zinc oxide, and titanium oxide at 1–100 mg.kg
−1
concentration on microbial
community and enzyme activity and found that after 30 days of exposure zinc oxide
and copper oxide did not affect or increase the soil enzyme activity but in contrast,
silver inhibited enzyme activity at high concentration, while titanium oxide did not
change significantly. Cao et al. (2017) found that silver nanoparticles influenced
mycorrhizal community in maize plant at 2.5 mg.kg
−1
concentration. They reported
that anti-oxidation activity of silver decreases diversity of mycorrhizal fungi,
resulted in decrease in colonization rate of root mycorrhizal fungi, reduction in soil
alkaline phosphatase activity and available phosphorus content to maize plant.
Silver nanoparticles also decrease the mutualistic relation of mycorrhizal fungi and
maize plant, which influenced the soil phosphoric cycle and affect soil fertility.
4.5 Effect on Microbial Community Structure
and Enzymatic Activities
The microbial community structure is majorly affected by the surrounding environment. Presence of metal nanomaterials in their surrounding directly interacted with
microbes and regulate their physiology by positive or negative route. Concentration
of nanoparticle is the most important factor, which plays a significant role in growth
or inhibition of microbial population and their enzymatic profiles. Different types of
enzymatic activity such as soil protease, dehydrogenase, urease, nitrogen fixation,
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…