115
been found that small size nanoparticles have higher dissolution rate in comparison
to bigger particles (Meulenkamp 1998; Bian et al. 2011; Mudunkotuwa et al. 2011;
Reed et al. 2012).
It has been reported that nanoparticles internalized into bacteria or it absorb on
the surface or associate with the membrane (Brayner et al. 2006; Kumar et al. 2011;
Dimkpa et al. 2012). The toxicity of nanoparticles toward bacteria was assessed in
reduction of colony forming unit, optical density measurement, and calculation of
minimum inhibitory concentration in many reports at monoculture system. But, at
community level, omics approach was used to provide genomic, proteomic, and
metabolomics information to understand the toxicity of nanoparticles at ground
level. Kaweeteerawat et al. (2015) reported toxicity of different metal oxide
nanoparticles to Escherichia coli. They observed the growth inhibition by CoO,
Co 3 O 4 , Cr 2 O 3 , CuO, Mn 2 O 3 , Ni 2 O 3 , and ZnO metal oxides due to membrane damage
and oxidative stress in the cell.
4.7.1 Reactive Oxygen Species (ROS) Production
Production of reactive oxygen species is the major cause of microbial damage. The
ROS react on phospholipids in cell membrane and oxidize the double bond in the
plasma membrane which increase membrane flexibility and permeability (Cabiscol
et al. 2010), Further, ROS damage the DNA by cross-linking and strand break in
bacteria. ROS can also disturb the proteins by development of sulfide bond between
sulfur-containing amino acids (Imlay 2003). In many reports, it has been reported
that UV radiation induces the production of ROS in bacteria (Kumar et al. 2011, Lu
et al. 2012). The effect of C 60 fullerene and carbon nanotubes (CNTs) on bioluminescent marine bacterium Vibrio fischeri was studied by Chae et al. (2011). They
found that under UV-A irradiation, ROS production and microbial inactivation
increased. The increase in ROS production under UV-A illumination decreased the
respiration rate, which is measured by degradation of 2-chlorophenol. In contrast,
Lyon and Alvarez (2008) found no toxicity of C 60 fullerene by photocatalytic ROS
production. They reported that the toxicity of C 60 fullerene is due to oxidation of
membrane lipids and proteins without ROS production.
4.8 Conclusion
The increasing utilization of nanomaterial-based consumer products and attraction
of human beings toward nanomaterial-based technology demand the higher production of nanomaterials. Increasing production also increases the release rate of such
nanomaterials into the environment, where they interact with the microbial community. The interaction of microbes and metal nanomaterial affects the microbial
community structure and physiology. The reduction or enhancement of microbial
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…
been found that small size nanoparticles have higher dissolution rate in comparison
to bigger particles (Meulenkamp 1998; Bian et al. 2011; Mudunkotuwa et al. 2011;
Reed et al. 2012).
It has been reported that nanoparticles internalized into bacteria or it absorb on
the surface or associate with the membrane (Brayner et al. 2006; Kumar et al. 2011;
Dimkpa et al. 2012). The toxicity of nanoparticles toward bacteria was assessed in
reduction of colony forming unit, optical density measurement, and calculation of
minimum inhibitory concentration in many reports at monoculture system. But, at
community level, omics approach was used to provide genomic, proteomic, and
metabolomics information to understand the toxicity of nanoparticles at ground
level. Kaweeteerawat et al. (2015) reported toxicity of different metal oxide
nanoparticles to Escherichia coli. They observed the growth inhibition by CoO,
Co 3 O 4 , Cr 2 O 3 , CuO, Mn 2 O 3 , Ni 2 O 3 , and ZnO metal oxides due to membrane damage
and oxidative stress in the cell.
4.7.1 Reactive Oxygen Species (ROS) Production
Production of reactive oxygen species is the major cause of microbial damage. The
ROS react on phospholipids in cell membrane and oxidize the double bond in the
plasma membrane which increase membrane flexibility and permeability (Cabiscol
et al. 2010), Further, ROS damage the DNA by cross-linking and strand break in
bacteria. ROS can also disturb the proteins by development of sulfide bond between
sulfur-containing amino acids (Imlay 2003). In many reports, it has been reported
that UV radiation induces the production of ROS in bacteria (Kumar et al. 2011, Lu
et al. 2012). The effect of C 60 fullerene and carbon nanotubes (CNTs) on bioluminescent marine bacterium Vibrio fischeri was studied by Chae et al. (2011). They
found that under UV-A irradiation, ROS production and microbial inactivation
increased. The increase in ROS production under UV-A illumination decreased the
respiration rate, which is measured by degradation of 2-chlorophenol. In contrast,
Lyon and Alvarez (2008) found no toxicity of C 60 fullerene by photocatalytic ROS
production. They reported that the toxicity of C 60 fullerene is due to oxidation of
membrane lipids and proteins without ROS production.
4.8 Conclusion
The increasing utilization of nanomaterial-based consumer products and attraction
of human beings toward nanomaterial-based technology demand the higher production of nanomaterials. Increasing production also increases the release rate of such
nanomaterials into the environment, where they interact with the microbial community. The interaction of microbes and metal nanomaterial affects the microbial
community structure and physiology. The reduction or enhancement of microbial
4 Nano-toxicity to Microbes: Potential Implications of Nanomaterials on Microbial…