Earthworms Could Help Reduce Antibiotic Resistance Genes in Soil

May 17, 2021

Earthworms improve the soil by aerating it, breaking down organic matter and mineralizing nutrients. Now, researchers reporting in ACS' Environmental Science & Technology have dug up another possible role: reducing the number and relative abundance of antibiotic-resistance genes (ARGs) in soils from diverse ecosystems. These results imply that earthworms could be a natural, sustainable solution to addressing the global issue of antibiotic resistance, the researchers say.

The overuse of antibiotics in humans and animals has caused ARGs to accumulate in soils, which could contribute to the rise in antibiotic-resistant infections. Earthworms consume tons of soil per year worldwide, and their guts have a unique combination of low-oxygen conditions, neutral pH and native microbial inhabitants that could have an effect on ARGs. However, the role of earthworms in the spread of antibiotic resistance has been controversial. Some studies in controlled settings suggest that their guts are hot spots for ARGs, which they can spread through soil with their movements, while other studies indicate that the earthworms' guts can reduce ARG abundance by destroying host bacteria and mobile genetic elements. To better understand the issue, Yong-Guan Zhu and colleagues wanted to compare the microbiomes and ARGs of earthworm guts with those of soils from diverse ecosystems across China.

The researchers collected earthworms and surrounding soil samples from 28 provinces in China. Then, they analyzed the composition of microbial communities in the worms' guts and the surrounding soil, finding that they differed between guts and soil and also among sites. In addition, the team found a lower number and relative abundance of ARGs in the earthworm guts than in the corresponding soil across all sampling sites. The earthworm guts also had lower levels of bacterial species that commonly host ARGs. These bacteria and their ARGs could be destroyed during digestion, or bacteria that live in the gut could out-compete them, the researchers say. In other experiments, they used controlled environments to show that the number and relative abundance of ARGs were higher in earthworm guts than in their feces, and that the addition of earthworms reduced ARGs in soil samples. These findings suggest that earthworms have the potential to mitigate these genes in soils as a form of natural bioremediation, the researchers say.

The authors acknowledge funding from the National Natural Science Foundation of China and the Marie Sk?odowska-Curie Actions Research Fellowship Program.

The paper's abstract will be available on May 12 at 8 a.m. Eastern time here: http://pubs.acs.org/doi/abs/10.1021/acs.est.1c00811

The American Chemical Society (ACS) is a nonprofit organization chartered by the U.S. Congress. ACS' mission is to advance the broader chemistry enterprise and its practitioners for the benefit of Earth and all its people.

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Video: Spring 2026 weather outlook for Wisconsin; What an early-arriving El Niño could mean

Northeast Wisconsin is a small corner of the world, but our weather is still affected by what happens across the globe.

That includes in the equatorial Pacific, where changes between El Niño and La Niña play a role in the weather here -- and boy, have there been some abrupt changes as of late.

El Niño and La Niña are the two phases of what is collectively known as the El Niño Southern Oscillation, or ENSO for short. These are the swings back and forth from unusually warm to unusually cold sea surface temperatures in the Pacific Ocean along the equator.

Since this past September, we have been in a weak La Niña, which means water temperatures near the Eastern Pacific equator have been cooler than usual. That's where we're at right now.

Even last fall, the long-term outlook suggested a return to neutral conditions by spring and potentially El Niño conditions by summer.

But there are some signs this may be happening faster than usual, which could accelerate the onset of El Niño.

Over the last few weeks, unusually strong bursts of westerly winds farther west in the Pacific -- where sea surface temperatures are warmer than average -- have been observed. There is a chance that this could accelerate the warming of those eastern Pacific waters and potentially push us into El Niño sooner than usual.

If we do enter El Nino by spring -- which we'll define as the period of March, April and May -- there are some long-term correlations with our weather here in Northeast Wisconsin.

Looking at a map of anomalously warm weather, most of the upper Great Lakes doesn't show a strong correlation, but in general, the northern tiers of the United States do tend to lean to that direction.

The stronger correlation is with precipitation. El Niño conditions in spring have historically come with a higher risk of very dry weather over that time frame, so this will definitely be a transition we'll have to watch closely as we move out of winter.