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Wastewater treatment plant effluents release microbiological pollutants, including the intI1 gene (integrases of class 1 integron), which has been proposed as a target for monitoring anthropogenic pollution in surface waters. This gene correlates with antibiotic resistance genes, making it an important proxy for genetic contamination in aquatic environments. It is currently unclear whether intI1 found in lake water is mainly present due to continuous seeding or if autochthonous bacteria harbor this gene. To better understand the fate and dynamics of class 1 integrons in aquatic systems, we resorted to classical limnological monitoring of intI1 (qPCR) over multiple years in three different size fractions: free‐living bacteria, particle‐attached bacteria, and zooplankton‐attached bacteria. We also conducted experiments to elucidate the impact of grazers on the abundance of intI1. The monitoring of different size fractions of the Lake Maggiore microbial community showed a particle‐bound lifestyle for intI1‐hosting bacteria. Most of these bacteria originated from both a wastewater effluent that discharges into Lake Maggiore and the lake water itself (amplicon sequencing). We hypothesize that these bacteria grow on particles in open waters, making them particularly vulnerable to grazing by large filter feeders such as Daphnia. Therefore, the presence of Daphniareduced the abundance of intI1 in lake water, whereas this was not true for other grazers such as Rotaria macruraor Poterioochromonassp. Our study shows that the food web structure and temporal changes in the lake influence the abundance of intI1 and consequently the assessment of anthropogenic pollution.

Conventional wastewater treatment processes have shown limited efficiency in removing emerging contaminants (EC), including organic micropollutants (OMPs) thus posing risks due to the safe discharge and reuse of wastewater effluent due to the presence of antibiotic-resistant bacteria and antibiotic resistance genes (ARG). Membrane technologies are being considered as alternative wastewater treatment strategies. In this context, gravity-driven membrane bioreactors (GD-MBRs) has been highlighted as a sustainable treatment process due to the low energy consumption. This study evaluates the efficiency of GD-MBR in removing selected OMPs (sulfamethoxazole, carbamazepine, and diclofenac) and the impact on ARGs abundance during the treatment of raw primary wastewater. Three GD-MBRs were operated in parallel at the same time, under different aeration conditions (no aeration, continuous aeration, and intermittent aeration). The OMPs were dosed continuously for all reactors after 78 days of operations. Over time, the efficiency of OMP removal decreased in all reactors. Following the addition of OMPs, the relative abundance of ARGs increased in the membrane biofilms of all three reactors. The no aeration (NA) GD-MBR exhibited the highest removal efficiency for sulfamethoxazole up to 64 %, while exhibiting a higher increase in sulfonamide resistance genes with 2 gene copies/16S rRNA in the permeate on day 105. This study sheds light on the effectiveness of GD-MBRs in mitigating OMPs under varying aeration conditions, offering insights for wastewater treatment strategies using GD-MBR.

The Black Sea is the largest meromictic sea with a reservoir of anoxic water extending from 100 to 1000 m depth. These deeper layers are characterised by a poorly understood fluorescence signal called “deep red fluorescence”, a chlorophyll a- (Chl a) like signal found in deep dark oceanic waters. In two cruises, we repeatedly found up to 103cells ml-1of picocyanobacteria at 750 m depth in these waters and isolated two phycoerythrin-rich Synechococcussp. strains (BS55D and BS56D). Tests on BS56D revealed its high adaptability, involving the accumulation of Chl ain anoxic/dark conditions and its capacity to photosynthesise when re-exposed to light. Whole-genome sequencing of the two strains showed the presence of genes that confirms the putative ability of our strains to survive in harsh mesopelagic environments. This discovery provides new evidence to support early speculations associating the “deep red fluorescence” signal to viable picocyanobacteria populations in the deep oxygen-depleted oceans, suggesting a reconsideration of the ecological role of a viable stock of Synechococcusin dark deep waters.

The Black Sea is the largest meromictic sea with a reservoir of anoxic water extending from 100 to 1000 m depth. These deeper layers are characterised by a poorly understood fluorescence signal called “deep red fluorescence”, a chlorophyll a- (Chl a) like signal found in deep dark oceanic waters. In two cruises, we repeatedly found up to 103cells ml−1of picocyanobacteria at 750 m depth in these waters and isolated two phycoerythrin-rich Synechococcussp. strains (BS55D and BS56D). Tests on BS56D revealed its high adaptability, involving the accumulation of Chl ain anoxic/dark conditions and its capacity to photosynthesise when re-exposed to light. Whole-genome sequencing of the two strains showed the presence of genes that confirms the putative ability of our strains to survive in harsh mesopelagic environments. This discovery provides new evidence to support early speculations associating the “deep red fluorescence” signal to viable picocyanobacteria populations in the deep oxygen-depleted oceans, suggesting a reconsideration of the ecological role of a viable stock of Synechococcusin dark deep waters.

Antibiotic resistance is a serious concern for public health. Farm environments are relevant reservoirs of antibiotic resistant bacteria and antibiotic resistance genes (ARGs), thus strategies to limit the spread of ARGs from farms to the environment are needed. In this study a broiler farm, where antibiotics have never been used for any purpose, was selected to evaluate if this measure is effective in reducing the ARGs load in farm environment (FE) and in meat processing environment (MPE). Faecal samples from FE and MPE were processed for DNA extraction. Detection and quantification of the 16S rRNA gene and selected ARGs (blaTEM, qnrS, sul2, and tetA) were carried out by PCR and digital droplet PCR (ddPCR), respectively. Generally, the relative abundance of the quantified ARGs in FE was similar or higher than that measured in intensive farms. Furthermore, apart for tetA, no differences in relative abundances of the other ARGs between FE and MPE were determined. These results suggest that the choice to not use antibiotics in broiler farming is not so effective to limit the ARGs spread in MPE and that further sources of ARGs should be considered including the preceding production phase with particular reference to the breeding stage.