Earthworms improve the soil by aerating it, breaking down organic matter, and mineralizing nutrients. Now researchers report in ACS ‘ Environmental science and technology discovered another possible role: reducing the number and relative abundance of antibiotic resistance (ARG) genes in soils of various ecosystems. These findings imply that earthworms could be a natural and lasting solution to solving the global problem of antibiotic resistance, the researchers say.
Overuse of antibiotics in humans and animals has led to a build-up of ARG in soils, which may contribute to the increase in antibiotic-resistant infections. Earthworms consume tons of soil per year around the world 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 in the soil with their movements, while other studies indicate that earthworm guts can reduce abundance. ARGs by destroying host bacteria and mobile genetic elements. To better understand the problem, Yong-Guan Zhu and his colleagues wanted to compare the microbiomes and ARGs of earthworm guts with those of soils in various ecosystems across China.
The researchers collected earthworms and samples from surrounding soil in 28 Chinese provinces. Next, they analyzed the makeup of microbial communities in the worms’ intestines and surrounding soil, finding that they differed between tripe and soil and also between sites. In addition, the team found a lower number and relative abundance of ARG in the bowels of earthworms than in the corresponding soil at all sampling sites. Earthworm guts also had lower levels of bacterial species that typically harbor ARGs. These bacteria and their ARGs could be destroyed during digestion, or the bacteria that live in the gut could outshine them, the researchers say. In other experiments, they used controlled environments to show that the number and relative abundance of ARGs was higher in the intestines of earthworms than in their feces, and that the addition of earthworms reduced the ARG in soil samples. These results suggest that earthworms have the potential to attenuate 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.
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