The Innovation Team of Soil Health Care of the Institute of Agricultural Resources and Regional Planning (IARRP) of the Chinese Academy of Agricultural Sciences (CAAS) and the CAAS-CIAT Sustainable Agriculture Joint Laboratory carried out research on the mechanism of microbial degradation of tetracycline, explored the degradation characteristics and pathways of tetracycline by fungi and bacteria, and speculated on the metabolic response mode of degrading-bacterium to tetracycline stress based on metabolomics.

The results were published in the journals Environmental Pollution and Microorganisms.

According to associate professor Ruan Zhiyong, in modern agricultural production, antibiotics such as tetracycline can enter the cultivated land system through various ways and become new pollutants in the soil. Antibiotic exposure will affect the biological activity and microbial community composition in the soil, thereby affecting soil health and the quality of cultivated land, and even indirectly causing potential risks to human health. Therefore, it is urgent to take effective measures to remediate antibiotic pollution.

Aiming at tetracycline pollution in cultivated soil, considering that microorganism bioremediation possess the advantages, such as environmental friendliness, low energy consumption, high efficiency to environmental pollutants, the team adopted the culturomics strategy to isolate abundant tetracycline-degrading strains from the tetracycline-contaminated soil. The degradation characteristics of the strain were studied through single factor optimization and response surface methodology, and the structural changes of tetracycline under the degradation of soil microorganisms and the subsequent antibacterial potency were analyzed through mass spectrometry and bacteriostatic assay.

The response of degrading-bacterium to tetracycline stress was analyzed at the metabolite level using non-target metabolomics: during the strain is stressed and damaged by tetracycline, the cell membrane accelerates the transport of nutrients from the extracellular space for amino acid metabolism, and produces acetyl-CoA and succinyl-CoA to enter the TCA cycle. In the TCA cycle, a large amount of nucleotides and amino acid precursors can be produced for the expression of tetracycline efflux proteins and degrading enzymes, and intracellular tetracycline is degraded after be excreted outside the cell. Cell damage and oxidative damage caused by tetracycline are alleviated by antioxidants such as taurine and protoporphyrin.

The study is of great significance for further understanding the mechanism of microbial degradation of tetracycline. It provides potential microbial resources for the bioremediation of tetracycline contamination in the cultivated land system, and provides new directions and ideas for maintaining the quality and health of arable land.

The research was funded by the National Key Research and Development Program of China, the National Natural Science Foundation of China (NSFC) and Science and Technology Innovation Project of CAAS .

Paper link:

https://doi.org/10.1016/j.envpol.2022.119299

https://doi.org/10.3390/microorganisms10030565