Something in the Water

Kaoru Ikuma (pictured, right), assistant professor in civil, construction and environmental engineering, is bringing clarity – clear, clean drinking water and clear answers – to environmental microbiology questions about water quality. She and her team are researching drinking water and waterbodies to improve public health protection.

Drinking water disinfection

Ikuma and her team are studying how pathogens in drinking water respond to chemical treatments. Conventional disinfection methods have for many years relied on chemical processes, and while methods typically work well, less is understood about cases when disinfection falters.

Ikuma is examining the biological reactions that chemical treatments cause.

“We understand the chemistry a lot better than the biology,” Ikuma said. “We are relying on the chemistry to work for every biological scenario. That’s where that gap exists, and I’m trying to fill that in.”

By using transcriptomics, Ikuma examines transcription of DNA to RNA to figure out whether the bacteria would be killed by chemicals – or just knocked down but capable of fighting back.

Add to the challenge that some bacteria are already resistant to chemicals or can become resistant. For example, E. coli can become resistant to chlorine in very controlled environments.

“We are coming to a point where we have to change disinfection,” Ikuma said. “The time is now to understand the biological reactions of pathogens better, so with the next generation of chemicals, we can make the best choices to ensure healthy drinking water.”

Antibiotic resistance in waterways

How concerned should we be about the spread of antimicrobial resistance from wastewater discharge? Ikuma’s team is following the stream of AMR into our waterways.

AMR starts in the gut of humans and animals, so the natural next stop is wastewater treatment plants. At treatment plants, wastewater is cleaned, disinfected and then released into rivers and lakes.

Ikuma’s team is investigating the behavior of AMR pathogens when they enter bodies of water. Disinfecting water kills bacteria, but AMR-coded DNA is capable of traveling on beyond host bacteria. AMR DNA could be transferring to other bacteria by horizontal gene transfer or being transported in water by simple absorption on particles.

Ikuma has been taking samples from the Skunk River outside Ames, Iowa, and examining studies of the Mississippi River to help shed light on AMR transfer in the environment.

“My main thing here is to say, does that extracellular DNA floating around matter? Because if it does, we need to really rethink disinfection of wastewater,” Ikuma said.