## 3 Results and Discussion
### The Coexistence Structure of PARGs with MGEs  
The co-occurrence frequency and genetic association of ARGs (and especially PARGs) and MGEs shows the transfer potential of ARGs as the treated sewage directly enters the receiving environment. The plasmid-related ARGs were more likely to coexist with MGEs. In HX WWTPs, most of the ACCs containing MGEs were plasmid sequences with only approximately 13% identified as chromosomal sequences (Figure S8). Plasmids are frequently transferred to new hosts even in the absence of selective pressure [64] and the combination of MGEs and plasmids facilitates the accumulation of ARGs in the environment, leading to widespread antibiotic resistance [7; 48; 65]. Plasmids and integrins easily recombine [66], and integrins share a gene cassette containing multiple ARGs, which is an important mechanism for multidrug resistance [67]. Class 1 integrins are the most common type of antibiotic-resistant clinical isolates [7], and class 1 integrin carrying ARGs are found in a variety of water environments [52; 68]. In this study, multiple contigs carry the class 1 integrase gene (_intII_) and at least one gene cassette, such as the _intII-tupA-orf1-tet_G-_tet_R-_flo_R-_sul_1 integration structure (Table S4). The interaction between different MGEs supports the rapid evolution of multidrug-resistant pathogens, and this requires further attention [7].  
PARGs were divided into two categories according to the different potentials of HGT. The first type had low HGT potential because they do not coexist on the same contig with MGEs, such as the bactracin resistance gene (_bac_A) and the multidrug resistance gene (_mex_D) (Table S2). The second type had high HGT potential with coexisting MGE combinations in separate compartments of the WWTP (Figure 5; Table S2) harboring _class A beta-lactamase_, _aac_Edelta1, _sul_1, and _sul_2. Coexistence combinations with _sul_1 and _sul_2 as the core ARGs were widely distributed in the WWTP, and ICEs were the most frequently occurring ARG-MGE combination (Figure 5; Table S2). For instance, the ICE6440-ICEP_aee690-sul_1-_qac_Edelta1 and ICE_Pmi_Chn3-_sul_2 coexistence structures were observed in the influent, activated sludge, and effluent of HX WWTP, and _K. pneumoniae_ may be a potential host for the combination of ICE_6440-ICEP_aee690-sul_1-_qac_Edelta1 (Figure 5). Meanwhile, there were frequent ARG-MGE combinations of _aph_(6)-I-_aph_(3\({}^{\prime\prime}\))-I-Tn5393-ICE_KKWG1 and _class A beta-lactamase_-ICE_6440_ (Figure S9). A fixed combination of the _aph_(3\({}^{\prime\prime}\))-I-_aph_(6)-I homolog, _str_A-_str_B was observed in wastewater under the pressure of five antibiotics [18]. ICEs are widespread in WWTPs and are the important medium for the transfer of various ARGs between human pathogens and environmental bacteria [48]. ICE carries out conjugative transfer between species and accumulates ISs or transposons on its border, and transfers them through conjugation [69; 70]. Bacteria that carry both ICEs and ARGs show stronger adaptability to high concentrations of antibiotics and have a higher risk potential for causing disease than bacteria that do not carry ICEs [71]. A similar pattern was found in CJ WWTP (Figures S8-S10) with the widespread PARG-MGE coexistence structure in Xinjiang WWTP, possibly explaining their persistence. The high-frequency co-occurrence of ICEs and PARGs revealed the high transfer potential and increased the risk of PARGs in WWTP.