## 4 Discussion
### Microbial Communities' Characterization
Previous studies reported that _Proteobacteria_ and _Bacteroidetes_ are part of the dominant phyla group in NP anaerobic degradation in river sediments [86; 97], _Proteobacteria_ and _Firmicutes_[98] are important in OP biodegradation in granular sludge and _Proteobacteria_, _Bacteroidetes_ and _Firmicutes_ can be the predominant phyla responsible for the dechlorination of chlorinated compounds like PCP [99; 100]. Therefore, in this work, the dominant phyla present in _P. australis_ rhizosphere of CWs may have contributed to the effective biodegradation/biotransformation of NP, OP and PCP. Moreover, [PERSON] et al. [85] reported that the abundance of _Bacteroidetes_, _Firmicutes_, _Proteobacteria_ and _Euyarchaeota_ varied greatly during PCP dechlorination process. The impact of OP to bacterial community of CWs substrate remains poorly understood. On the other hand, a few previous studies indicated that NP addition showed no or little impact on aquatic bacterial community structure [101; 102; 103]. In contrast, [PERSON] et al. [104] and [PERSON] et al. [105] found that NP affected soil bacterial community structure. Moreover, [PERSON] et al. [86] verify that NP presence and biodegradation altered the sediment bacterial community structure at the phylogenetic levels of phylum, class and genus. Nevertheless, compounds concentrations can affect microbial communities' response. [PERSON] et al. [106] indicated that soil microbial community did not change significantly at NP concentration below 90 \(\upmu\)g\(\cdot\)g\({}^{-1}\), but changed at 270 \(\upmu\)g\(\cdot\)g\({}^{-1}\). [PERSON] et al. [86] reported that an NP concentration of 100 \(\upmu\)g\(\cdot\)g\({}^{-1}\) had a strong impact on sediment bacterial community structure at phylogenetic levels of phylum, class and genus. Regarding OP toxicity, [PERSON] et al. [98] reported a toxicity effect for degrading microorganisms present in granular sludge at a concentration of 220 \(\upmu\)g\(\cdot\)L\({}^{-1}\), but not for concentrations of 120 and 30 \(\upmu\)g\(\cdot\)L\({}^{-1}\), the toxicity affecting the degradation rate of OP. Comparison of substrate exposed to doped stream water with that of control systems showed that several specialist genera were enriched following exposure to the alkylphenol compounds, suggesting a growth benefit for target compounds biodegradation. In doped systems substrate, the three more abundant specialist genera were _Methylolenza (methyloliaceae_ family), _Hyplomicrobium (Inphomicrobiaceae_ family) and _Methylolilus (methyloliaceae_ family). The genera _Methylolenza and Methylolilus_ are from the same family, the _Methyloliaceae_. Members of this family have been previously described to utilize some organic pollutants as an energy source [107], degrading benzofilm-ethyl from activated sludge [108], methanol present in industrial sewage [109] and PAH [110]. [PERSON] et al. [110] have suggested that this family might have the ability to use ring-hydroxylating-dioxygenase (RHD\(\alpha\)) genes in pollutants degradation. These genes encode for dioxygenenses and monooxygenenses enzymes, that are involved in aerobic degradation pathways [111]. According to [PERSON] et al. [112], the hydroxyles and ring-cleavage dioxygenase are involved in long-chain alkylphenol degradation pathways. This same study identified in _Methylolacterium_ genus, from _Methyloliaceae_ family, the presence of the genes that encode these key enzymes in alkylphenol degradation pathways. Moreover, _Methylolacillus_ genus from this family has been linked to degradation of a variety of phenolic compounds [113]. Considering the great representation that the members of _Methyloliaceae_ family have in groups of \"specialist genera\" in the presence of NP and OP, members of _Methyloliaceae_ family probably had an important role in the degradation of NP and OP in the present study.