Metals vs Microbes- the Oligodynamic Effect!

“Discussion is an exchange of knowledge; argument an exchange of ignorance.”
Robert Quillen

Well, it was a normal evening adda until we noticed something new in the room, a water bottle! This reddish brown bottle gave an interesting turn to the conversation. The discussion though started on a lighter note with jokes and speculations soon made us ponder as to why someone would actually choose something made of Copper instead of plastic like most of us do. Few minutes on the internet gave us the term “Oligodynamic Effect”.

Oligodynamic Effect is defined as “a toxic effect of metal ions on living cells, algae, molds, spores, fungi, viruses, prokaryotic and eukaryotic microorganisms, even in relatively low concentrations.” In simple words, some metals have the intrinsic ability to kill microbes, i.e., be antimicrobial and biocidal. What I find very remarkable is that the Oligodynamic effect is not something new and has been known to us since ages! Since a long time, it has been believed that water kept in certain metal pots is safer to drink and is less contaminated with microbes. It is quite interesting how the ancient civilizations exploited this idea even before the concept of microbes was known to mankind. Even the ancient Indian medical text Sushruta Samhita endorsed the use of certain specific metals in surgical procedures to prevent infection. In modern times, the effect was observed by Karl Wilhelm von Nägeli, although he did not identify the cause.

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Copper vessel (Source: Google)

In this context, it would be good to know the story of a physician, Victor Burq.  When multiple cholera outbreaks hit the city of Paris in the 19th century, Burq was shocked when he learned that mysteriously most of the copper workers in the area had dodged the disease! On investigating further, he came to know that jewelers, musicians who played brass instruments and goldsmiths were less severely affected by the disease. To give you an idea, in the 1865 Paris epidemic, 6,176 deaths were reported because of cholera (out of a population of approx. 1,677,000 people—that’s 3.7 people out of every 1,000). But of the 30,000 who were involved with the copper industries, only 45 died! Burq’s curiosity lead him to collect data from other cities and countries with a similar story and finally in 1867, he concluded  at the French Academies of Science and Medicine that copper or its alloys (brass and bronze) applied to the skin in the cholera epidemic are effective means of prevention which should not be neglected.”

I also read about few recent studies on the topic by scientists from Nepal. Shahi et al. (1996) tested five types of traditional pots for the bactericidal action against E. coli (ATCC25922). Their experiments showed that copper, silver and brass pots were found to be very effective against the E. coli culture while steel and aluminium pots were found less effective toward the E. coli isolates. A more recent 2009 study by researchers from Nepal and South Korea showed Copper was more effective towards E.Coli than Silver or Brass. A very important question that’s yet to be answered is the mechanism. Now, what makes the metals so special?

Quoting directly from the paper by Shrestha et al. (2009): “The exact mechanism of this action is still unknown but some data suggest that the metal ions denature protein of the target cells by binding to reactive groups resulting in their precipitation and inactivation. The high affinity of cellular proteins for the metallic ions results in the death of the cells due to cumulative effects of the ion within the cells”. The number of various possible mechanisms for different metals reported is many and kind of impossible to list down. Some mechanisms for copper’s activity include disruption of respiratory chain leading to impaired mechanism and alteration of the 3D protein/enzyme structures such that they are unable to function normally. A research on the H1N1 flu lead to a hypothesis that Copper’s antimicrobial action attacks the overall structure of virus. A proposed mechanism for silver is that it inactivates enzymes by binding with sulfhydryl groups to form silver sulphides or sulfhydryl-binding propensity of silver ion disrupts cell membranes, deactivates proteins and impedes enzyme activities. Quite interestingly, studies have also shown that in order to improve the oligodynamic effect, more than one metal can be used in combination for a synergistic effect on the microbes. One such possibility is using copper and silver together where positively charged copper ion distorts the cell wall of microorganisms by binding to negatively charged groups and allowing the Silver ion into the cell thus increasing the efficiency of the process.

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One of the proposed mechanisms for Oligodynamic Effect of Copper (Source: CuVerro)

Another interesting thing I came across while reading on this was “metal resistance” which is pretty much similar to something we are familiar with, “antibiotic resistance.” The reason for the resistance is also quite similar like over-exploitation and abuse of metals for this purpose. (Studies have also reported co-existence of antibiotic and metal resistance).

To conclude, the oligodynamic effect is still a topic under active research and there’s a lot to read and know on the topic. Intensive research is going on to identify properly the molecular mechanisms behind it and the safety issues associated with the use of metals. I would end this article with the words of Michael Schmidt, a professor of microbiology and immunology at the Medical University of South Carolina, “What happened is our own arrogance and our love of plastic and other materials took over. We moved away from copper beds, copper railings, and copper door knobs to stainless steel, plastic, and aluminum.” According to him, using copper along with standard hygiene protocols can  reduce bacteria in health care settings by 90%!

By Raibat Sarker, Department of Chemistry, Indian Institute of Science Education and Research Bhopal.

References:

  • https://en.wikipedia.org/wiki/Oligodynamic_effect#cite_ref-1
  • https://en.wikipedia.org/wiki/Antimicrobial_properties_of_copper
  • https://www.tested.com/science/life/453961-oligodynamic-effect-how-some-metals-kill-bacteria/
  • https://www.vice.com/en_us/article/xgqkyw/copper-destroys-viruses-and-bacteria-why-isnt-it-everywhere
  • Shahi, R., M.P. Baral and T.M. Pradhananga. 1996. Oligodynamic action of traditional Nepalese water pots against E. coli (ATCC 25922). Paper presented at the 2nd international seminar on water and environment, Kathmandu, Nepal.
  • Oligodynamic Action of Silver, Copper and Brass on Enteric Bacteria Isolated from Water of Kathmandu Valley (Rajani Shrestha1, Dev Raj Joshi2, Jyotsna Gopali1 and Sujan Piya3)

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“The saddest aspect of life right now is that science gathers knowledge faster than society gathers wisdom.” -Isaac Asimov


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About the author: Raibat is a 3rd year Integrated MS student at the Department of Chemistry, IISER Bhopal. He is also a KVPY fellow and a recipient of the DAAD WISE fellowship 2020. Apart from being a big foodie and FCB fan, he loves trekking and camping. When he’s not sciencing , eating or complaining about his bad luck, you will find him hooked into novels or planning his next trek! Also, he is associated with The Qrius Rhino.


Author: Raibat Sarker

A BS-MS (Chemistry) student and a KVPY fellow at IISER Bhopal who founded The Qrius Rhino in March 2018.. He was associated with the IISER Bhopal iGEM 2020 team which went on to win the gold medal in the jamboree. He is passionate about trekking and camping, apart from being a foodie and die-hard FCB fan. When not sciencing, eating, or complaining about his bad luck, you will find him hooked into novels or planning his next trek!

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