Distribution and transfer of antibiotic resistance genes in different soil-plant systems

Abstract

The extensive application of farm manure that is contaminated with pharmaceutical antibiotics not only causes substantial soil pollution but additionally leads to the input of antibiotic resistance genes (ARGs) into the soil. These ARGs would proliferate and affect human health via the food chain. The effects of cultivated crops and wild plants on ARGs in rhizosphere soil are unclear. Therefore, we chose potted plants of cultivated crops (pakchoi, lettuce, corn) and wild plants (barnyard grass, crabgrass, dog tail), and set up test groups, i.e., treatment group, antibiotic-contaminated soil; control group, no antibiotic-contaminated soil; and a blank group without plants. The aim was to explore differences in the distribution and transfer of ARGs in the soil-plant system between cultivated crops and wild plants and at the same time to explore the influence of bacterial community evolution on ARGs in the rhizosphere soil of cultivated crops and wild plants. We concluded that under the pressure of antibiotic selection, ARGs can be transferred to the root endophytes of plants through the soil and further to the phyllosphere of plants, and cultivated crops such as pakchoi and wild plants barnyard grass have a strong ability to transport ARGs. Regardless of cultivated crops or wild plants, the abundance of ARGs in rhizosphere soil can be substantially reduced by 66.53 ~ 85.35%. Redundancy analysis and network analysis indicated that bacterial community succession is the main mechanism affecting changes of ARGs in rhizosphere soil. The reduction of Firmicutes due to the plant was the main factor responsible for the reduction of the abundance of ARGs in rhizosphere soil. The tetA, tetG, tetX, sul2, and qnrS genes are highly related to some potential pathogens, and the health risks they bring are a red flag that deserves attention.

Keywords: Bacterial communities; Cultivated crops; Pig manure; Plant-soil system; Rhizosphere soil; Wild plants.