Global profiling of antibiotic resistomes in maize rhizospheres

Abstract

The spreading of antimicrobial resistance (AMR) in crops and food products represents a global concern.In this study, we conducted a survey of resistomes in maize rhizosphere from Michigan, California, the Netherland, and South Africa, and investigated potential associations with host bacteria and soil management practices in the crop eld. For comparison, relative abundance of antibiotic resistance genes (ARGs) is normalized to the size of individual metagenomes. Michigan maize rhizosphere metagenomes showed the highest abundance and diversity of ARGs, with the detection of blaTEM-116, blaACT-4/-6, and FosA2, exhibiting high similarity (≥ 99.0%) to those in animal and human pathogens. This was probably related to the decade-long application of manure/composted manure from antibiotictreated animals. Moreover, RbpA, vanRO, mtrA, and dfrB were prevalently found across most studied regions, implying their intrinsic origins. Further analysis revealed that RbpA, vanRO, and mtrA are mainly harbored by native Actinobacteria with low mobility, while a group of dfrB genes are adjacent to the recombination binding sites (attC), which together constitute mobile gene cassettes, promoting the transmission from soil bacteria to human pathogens. These results suggest that maize rhizosphere resistomes can be distinctive and affected by many factors, particularly those relevant to agricultural practices.

From a binding module to essential catalytic activity: how nature stumbled on a good thing

“…An independent study found that DfrB genes are abundant in the maize rhizosphere (microbes associated with the roots of corn), suggesting that DfrB are intrinsic to this environment. 110 Natural freshwater environments were also shown to be a major reservoir of DfrB variants. 111,112 In all these cases, DfrB were identified in environments that have presumably not been exposed to TMP such that selective pressure does not justify their presence.…”