## 3 Results and Discussion
### Abundance of Antibiotic Resistance Genes  
Due to the non-cultivability nature of most water's bacterial organisms, total bacterial abundance was evaluated by quantifying the housekeeping gene 16S rRNA. Additionally, the abundance of _intl_1 and ARGs (_su_1 and _bla_ TEM) was quantified in all PBRs (Figure 8). Results show that at the beginning of the experiment, in both the CV and C\(-\) PBRs, the abundance of total bacteria was at least 3 log higher than the ones quantified by cultivable methods (Figures 7 and 8, respectively). However, this difference was much higher in the C+ PBR, 4.1 logs, indicating a high abundance of non-cultivable bacteria in consortia with _C. vulgaris_, which was kept stable during the 9 d of the experiment. At the end of the experiment, the ratio of abundance of the 16S rRNA gene and total heterotrophs was reduced in the CV, and slightly in the C\(-\) PBR, possibly due to the release of algae metabolites that favored the cultivability of some UWW bacterial groups. Figure 7: Quantification of _E. coli_, other faecal coliforms except _E. coli_, and total heterotrophs over time (d) for each PBR: \(\blacksquare\) CV (C. _valgaris_ + UWW); \(\blacksquare\) C+ (C. _vulgaris_ + autoclaved UWW); and \(\blacksquare\) C\(-\) (raw UWW). Results are expressed in log (CFU 100 mL\({}^{-1}\)) (average \(\pm\) standard deviation). Bars from the same group of bacteria with a common superscript letter are not statistically different (two-way ANOVA followed by Tukey post hoc test \(p>0.05\)). The _intl1_ gene encoding the class 1 integrins integrase, found in pathogenic gram-negative and commensal bacteria of humans and domestic animals, is commonly used as a marker for anthropogenic pollution [61]. Moreover, this gene is usually related to ARGs, namely _su1_ since _intl1_ encodes for an integrase responsible for the insertion and excision of exogenous gene cassettes [62]. The ARGs _bla_TEM and _su1_ are related to beta-lactams and sulfonamides resistance, respectively [32; 63]. The reduction of _intl1_ and ARGs can occur via the removal of living cells containing these genes and the loss of ARG-containing plasmids [24; 62]. Although the _C. vulgaris_ inoculum used in this study did not have an environmental origin, it was revealed to be non-axenic and possibly in a consortium with bacteria carrying _intl1_, _su1_, and _bla_TEM genes, with an abundance of 7.4 \(\pm\) 0.2, 7.6 \(\pm\) 0.1 and 5.0 \(\pm\) 0.2 log (gene copy number 100 mL\({}^{-1}\)), respectively (C+, Figure 8). In terms of microalgae's ability to reduce _intl1_ and ARGs from UWW, _C. vulgaris_ appears to not have any significant (_p_ < 0.05) effect in terms of log reduction, RRG and prevalence of these genes (CV and C+, Figure 8, Table 4). In contrast, AMS from the C\(-\) PBR may have contributed to the reduction of the _intl_1 (0.5 log reduction, \(p\) < 0.05) and _bla_TEM (0.6 log reduction, \(p\) < 0.05) genes abundance after 9 d, corresponding to percentages of RRG of 70.4 \(\pm\) 9.2%, 69.2 \(\pm\) 7.5%, and 75.7 \(\pm\) 1.6%, for _intl1_, _su1_, and _bla_TEM respectively (Figure 8, Table 4). Additionally, a significant decrease in the prevalence of the _bla_TEM gene after 9 d was registered in the C-PBR (Table 4). The obtained results are in line with similar studies. As observed by [PERSON] et al. [37] with _Galdieria sulphuraria_, AMS treatment also reduced _intl_1 abundance, indicating that the microalgal treatment could reduce the spread of resistance. Additionally, AMS's ability to reduce _bla_TEM abundance was 0.1 log higher when compared to the _Chlorella sorokiniana-Brevundimonas basaltic_ consortium, as studied by [PERSON] et al. [40]. Recently, [PERSON] et al. [24] observed that a _C. vulgaris -B. licheniformis_ consortium was able to promote _su1_1 reduction of abundance due to the efficient removal of exogenous plasmids carrying ARGs such as _su1_.