Metagenomic Characterization of Microbial Pollutants and Antibiotic- and Metal-Resistance Genes in Sediments from the Canals of Venice
Curran J.F.[1]; Zaggia L.[2]; Quero G.M.[3];
The spread of fecal pollutants and antibiotic resistance in the aquatic environment
represents a major public health concern and is predicted to increase in light of climate change
consequences and the increasing human population pressure on the lagoon and coastal areas. The
city of Venice (Italy) is affected by diverse microbial pollution sources, including domestic
wastewaters that, due to the lack of modern sewage treatment infrastructure in the historical city
center, are released into canals. The outflowing jets of its tidal inlets thus represent a source of
contamination for the nearby beaches on the barrier island separating the lagoon from the sea.
Metagenomic analyses of DNA extracted from sediment samples from six sites in the canals of the
city’s historic center were undertaken to characterize the microbial community composition, the
presence of fecal microbes as well as other non-enteric pathogens, and the content of genes related
to antibiotic (AB) and heavy metal (HM) resistance, and virulence. The six sites hosted similar
prokaryotic communities, although variations in community composition likely related to oxygen
availability were observed. All sites displayed relatively high levels of fecal contamination,
including the presence of Fecal Indicator Bacteria, sewage- and alternative feces-associated bacteria.
Relatively high levels of other potential pathogens were also found. About 1 in 500 genes identified
at these sites are related to AB and HM resistance; conversely, genes related to virulence were rare.
Our data suggest the existence of widespread sediment microbial pollution in the canals of Venice,
coupled with the prevalence of ARGs to antibiotics frequently used in humans as well as of HMRGs
to toxic metals that still persists in the lagoon. All of this evidence raises concerns about the
consequences on the water quality of the lagoon and adjacent marine areas and the potential risks
for humans, deserving further studies.
2022 - Journal article
Water (Basel) 14 (2022). doi:10.3390/w14071161
Keywords: microbial pollution; bathing waters; shotgun metagenomics; Venice Lagoon; antibiotic resistance; heavy metal resistance