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380 || AWSAR Awarded Popular Science Stories - 2019
modifications, physiological alterations, etc. In short, the demand for device techniques to combat problematic microbes and AMR is sky-high so as to deal with the severity of the problems.
In this aspect, sonophotocatalysis (SPC), an advanced oxidation process (AOP), seems to have great potential in tackling the issue. We, at the Chemical and Bioprocess Engineering Laboratory of School of Biotechnology, KIIT University, Bhubaneswar, aim to reduce the microbial burden and AMR in engineered water bodies using SPC and associated techniques. SPC is very unlikely as far as our experimental results are concerned, as the setup is simple but with complex outcomes for microbes and the sustenance of microbes. As the name suggests, SPC consists of nanoparticles (NPs) in a slurry form with the synergistic effects of light and sound energy. The energy contributed to the surface of the NPs leads to jumping of electrons from their designated
place called ‘valance band’
to an unstable state called
‘conduction band’. This
reaction in the proximity of water
molecules yields highly baneful
reactive oxygen species (ROS)
such as hydroxyl radicals
(•OH), superoxide anions (O2•),
hydrogen peroxide (H2O2), etc.
Also, sonication, a physical
process, helps to stimulate the
overall process of disinfection
via a process called acoustic
cavitation. We synthesized and
employed iron (Fe)-doped zinc
oxide (ZnO) (Fe:ZnO) NPs for
SPC as they were found to be
very effective against a broad
range of waterborne pathogens including those carrying AMR genes. So far, we have optimized the SPC system on the lab scale against different virulent and AMR strains of
Salmonella and Shigella species at loading that exceeds real contaminated water. Another advantage of Fe:ZnO NPs is that they are active under natural sunlight as well as artificial visible light, making them an attractive option for the decontamination of water regardless of the accessibility of sunlight.
A detailed study to delineate the definitive mechanism of SPC on how the bacteria were killed revealed that the detrimental effect of ROS generated during the SPC process caused hampering at different subcellular levels of bacteria including DNA and protein damage. However, like any other AOP, SPC’s initial attack was launched at the primary shield of the bacteria, the membrane, demonstrated using fluorescent and electron microscopy. The damage intensity was found to have direct implications on the metabolic activity of the bacteria tested, signifying the hostile environment created by the formation
of multiple ROS during SPC. In the simulated as well as real water conditions (i.e. along with chemical contaminants present in other water sources), SPC proved to be efficient enough, suggesting its applicability for real-world purposes.
The story of antibiotics dates back to the early twentieth century when Alexander Fleming discovered penicillin in serendipity and then called it ‘wonder drug’ as it was used to treat infections caused during the First World War. However, its use without proper rubric led us to a state of a quandary as microbes have now started
to outmanoeuvre the efficacy of antimicrobial agents. Similarly, when we take into account the ability of microbes to adapt and evolve while acquiring AMR genes in highly stressful
   What if water, the elixir of life, and wastewater treatment plants (WWTPs) are one of the major culprits behind this evolution and dissemination of AMR? Sad, but true! Although designed to remove contaminants from water, most of the WWTPs are failing to stand against the brilliance of microbes
in overriding the treatment facilities.
  





































































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