| Dares and prospects | Description |
| Capacity improvement | Despite the main signs of progress, the elimination potentials of antibiotics in BESs are comparatively low taking into account their future utilization in realistic polluted waters. Enhancing the electron transfer capability remains crucial to deal with such trouble [85] [86] [87] . Electrodes are the habitats of exoelectrogens and dictate the activity of microorganisms and the global efficiency of BESs [88] [89] [90] . Consequently, low-cost and durable electrode materials with superior conductivity and biocompatibility remain to be sophisticated [91] [92] [93] . Biochar and its modification materials as well as other cost-effective carbon-based electrodes could be excellent solutions [94] [95] [96] . Juxtaposing diverse electrodes in terms of their impact on microbial community and electron transfer has to be examined in the next years [97] [98] [99] . Moreover, adding electron transfer mediators could increase the elimination capability, and the interplay of electrochemically active microbes, electrodes, and electron transfer mediators warrants further studies [100] [101] [102] . |
| Biocatalyst mechanism | The functional species matching with numerous representative antibiotics were well illustrated by Yan et al. [84] . However, the pathway implied in the electron transfer between pathogens and electrodes and among mixed bacteria stays vague and the metabolic mechanisms of functional genes for antibiotics detoxification request to be illustrated in the next years [103] [104] [105] . Omics techniques, like metagenomics, metaproteomics, and metabolomics, might be conducive for the exploration of functional genes concerning the electron transfer and metabolic routes of antibiotics to reveal the potential proteins mediating electron transport and to define the potential enzymes catalyzing metabolic reactions of antibiotics. Further, how to efficaciously dominate the generation of functional biofilms and to improve the expression of relevant functional genes under various working factors have to attract more attention in the next studies. |
| ARG investigation | Considering the diversity of ARGs and the difference of ecological parameters of diverse ARGs, more examinations of more types of ARGs and their interaction in BESs are needed [106] [107] [108] . High-throughput quantitative polymerase chain reaction (PCR) stays a powerful procedure that could be employed to simultaneously quantify nearly 300 types of ARGs [109] [110] [111] . Further, functional metagenomics possess an essential contribution in detecting obscure ARGs. Consequently, high-throughput quantitative PCR and functional metagenomics are predictable to light scientific troubles about biofilms in BESs comprising the abundance and diversity of ARGs, route of horizontal gene transfer, and dissimilarities of ARG expression under single and multi-antibiotics during long-term operation. The co-existence of antibiotics and additional emerging contaminants (like pharmaceuticals and personal care products) should be noticed in the realistic environment. As a result, besides the feasibility of BESs for eliminating co-existent contaminants, the influence of co-existent contaminants on ARGs in electroactive biofilms should be considered. |
| System development | Numerous investigations were realized in simulative aquatic mediums; however, the emerging contaminants of antibiotics are omnipresent and frequently established to be readily concentrated in solid matrixes (like sediments, sludge, and soil). The development of sediment MFCs and plant MFCs or other solid BESs might be an important basis to examine such problems. Specific BESs remain to be suggested for numerous surroundings implying the study of the elimination capability and crucial parameters of antibiotics-containing solid matrixes. Furthermore, the coexistence of antibiotics pollutants and other contaminants (like heavy metals) is pandemic. Heavy metals pose a co-selective pressure on ARGs. Biocathodes have proven to be a good platform for the reduction of metals and antibiotics. Thus, it requires to be examined if biocathodes are a good choice for the treatment of matrixes carrying both antibiotic pollutants and heavy metals and for the release of the co-selective pressure through a rapid transformation. |