Drinking water quality and safety is strictly regulated and constantly monitored, but little is known about the microorganisms inhabiting drinking water treatment plants (DWTPs). This lack of knowledge prevents optimization of designs and operational controls. Here we investigated the drinking water microbial community harbored by a groundwater-derived DWTP, involving mineral and vegetal granular activated carbon filters (GACs). We used 16S rRNA gene sequencing to analyze water microbiome variations through the potabilization process, considering (i) different GAC materials and (ii) time from GAC regeneration. Our results revealed the predominance of Cand. Patescibacteria, uncultivable bacteria with limited metabolic capacities and small genomes, from source to downstream water. Microbial communities clustered per sampling date, with the noteworthy exception of groundwater samples. If the groundwater microbiome showed no significant variations over time, the community structure of water downstream GACs (both mineral and vegetal) seemed to be affected by time from GAC regeneration. Looking at a finer scale, different GAC material affected microbiome assembly over time with significant variation in the relative abundances of specific taxa. The significance of our research is in identifying the environmental microorganisms intrinsic of deep groundwater and the community shift after the perturbations induced by potabilization processes. Which microorganisms colonize different GACs and become abundant after GACs regeneration and over time is a first step toward advanced control of microbial communities, improving drinking water safety and management of operational costs.

Molecular-based approaches for species identification and delimitation strongly rely, in terms of universality and efficiency, on the selected markers. Conventionally, when adopting a DNA barcoding approach to discriminate (or identify) metazoans species, the marker choice falls on the 658 base pair region at the 5ʹ end of the mitochondrial COI gene. However, a growing number of studies suggest to use alternative and more variable genetic regions, even from the same gene, such as the 3ʹ end of the COI. In this work, we compared the identification performance of the 5ʹ and 3ʹ end COI regions on a large sequence dataset of odonate species, an order of arthropods among the most studied in terms of conservation importance for aquatic ecosystems. The genetic datasets comprised a total of 236 specimens, 113 species, 51 genera and 12 families spanning the two odonate suborders Zygoptera and Anisoptera, and were analysed under an integrative multiple approach including descriptive statistics and variability of the sequences, phylogenetic reconstructions, DNA-based species delimitations, genetic distances, identification of diagnostic characters and saturation plots. All analyses were congruent in recovering the COI-3ʹ region to be slightly more variable than the COI-5ʹ one, and both regions showed a saturation of transversion at the third codon position. However, phylogenetic reconstructions, genetic distances, and diagnostic characters identification resulted in a similar discrimination power for the two COI regions. Therefore, the COI-3ʹ region does not add much information to the standard COI-5ʹ barcode region, which has in turn largely been demonstrated to successfully delineate invertebrate communities through DNA and eDNA metabarcoding, and to have a much more extensive taxonomic coverage in public databases. Overall, the DNA barcoding inventory assembled in this study will provide valuable insights into the systematics and conservation of many odonate species with implications for future DNA and eDNA monitoring-based studies.

Aquaculture significantly contributes to the growing demand for food worldwide. However, diseases associated with intensive aquaculture conditions, especially the skin related syndromes, may have significant implications on fish health and industry. In farmed rainbow trout, red mark syndrome (RMS), which consists of multiple skin lesions, currently lacks recognized aetiological agents, and increased efforts are needed to elucidate the onset of these conditions. Most of the past studies were focused on analyzing skin lesions, but no study focused on water, a medium constantly interacting with fish. Indeed, water tanks are environmental niches colonized by microbial communities, which may be implicated in the onset of the disease. Here, we present the results of water and sediment microbiome analyses performed in an RMS-affected aquaculture facility, bringing new knowledge about the environmental microbiomes harbored under these conditions. On the whole, no significant differences in the bacterial community structure were reported in RMS-affected tanks compared to the RMS-free ones. However, we highlighted significant differences in microbiome composition when analyzing different samples source (i.e., water and sediments). Looking at the finer scale, we measured significant changes in the relative abundances of specific taxa in RMS-affected tanks, especially when analyzing water samples. Our results provide worthwhile insight into a mostly uncharacterized ecological scenario, aiding future studies on the aquaculture built environment for disease prevention and monitoring.