Photo/IllutrationThe Asahi Shimbun

  • Photo/Illustraion

While cicadas are mostly known for their distinctive peal in summer, they turn out to be highly adept at killing germs.

Scientists at Kansai University are studying the creatures, specifically the structure of their wings, in the hope of creating an ecofriendly alternative to traditional antibiotics.

Antimicrobial products that use drugs to suppress the multiplication of bacteria are common household items, including sanitary toilet seats. They are also used in bacteria-resistant escalator handrails and clothes that are less likely to develop the stench of sweat.

Over time, however, germs may develop a resistance to the drugs used in the products, as has happened with antimicrobial agents in medicated soap.

A research team led by Takeshi Ito, a professor of nanophysics and engineering at the university, is focusing on the transparent sections of the wings of “Cryptotympana facialis” cicadas, a common species in Japan, to create a structure to kill bacteria.

The new treatment the team is testing has drawn attention for its low environmental impact. It mimics the structure of the wings instead of using drugs to realize antibacterial effects.

Australian researchers earlier found “Pseudomonas aeruginosa” bacteria perished when they were poured onto the wing sections, but it remained unknown if the structure induced their deaths.

A multitude of fine protuberances line the transparent sections of the wings like the bumps on the insoles of acupressure massage sandals.

Ito and his colleagues used a silicon substrate to build a nanostructure, a nanometer-size structure, shaped like a cicada wing.

They placed bumps about one-1,000th the thickness of a human hair at regular intervals on the substrate.

Liquid containing colon bacilli was poured onto the artificial structure, where the bacteria were grown and checked for changes in population. The study found the live bacteria shrank, down to only one-100,000th of the initial count in the most dramatic case.

“I hypothesize the colon bacilli injure and puncture the cell membranes as they try to move around on the nanostructure, whereupon they die from a drain of bodily fluids,” Ito said.

There have been calls in recent years to create antimicrobial treatment methods that contain lower amounts of drugs.

“The issue of the emergence of drug-resistant bacteria induced by overuse of antibiotics is being raised in the pharmaceutical field,” said Jun Sawai, a professor of food hygiene at the Kanagawa Institute of Technology who is well-versed in the control of microorganisms. “Similar concerns have also been raised in the field of antimicrobial treatment.”

Sawai, who studied bacteria stuck to the surface of a smartphone coated with an antimicrobial film, said the counts of colon bacilli and other common bacterium species were small, but highly resistant germs of a group called spore-forming bacteria, which can withstand typical antimicrobial agents, survived.

Some spore-forming bacteria, including botulinum bacteria and Welch bacilli, can cause food poisoning.

The finding led Sawai to rethink the design of antibacterial agents.

“Despite the remaining technological challenges, antimicrobial treatment should shift from being about kneading antibacterial agents into the entire material to just treating surfaces,” Sawai said.