Chemical mixtures and fluorescence in situ hybridization analysis of natural microbial community in the Tiber river

Abstract

The Water Framework Directive (WFD) regulates freshwater and coastal water quality assessment in Europe. Chemical and ecological water quality status is based on measurements of chemical pollutants in water and biota together with other indicators such as temperature, nutrients, species compositions (phytoplankton, microalgae, benthos and fish) and hydromorphological conditions. However, in the current strategy a link between the chemical and the ecological status is missing. In the present WFD, no microbiological indicators are foreseen for integrating the different anthropogenic pressures, including mixtures of chemicals, nutrients and temperature changes, to provide a holistic view of the freshwater ecosystem water quality. The main aim of this work was to evaluate if natural microbial populations can be valuable indicators of multiple stressors (e.g. chemical pollutants, temperature, nutrients etc.) to guide preventive and remediation actions by water authorities. A preliminary survey was conducted to identify four sites reflecting a contamination gradient from the source to the mouth of a river suitable to the objectives of the European Marie Curie project, MicroCoKit. The River Tiber (Italy) was selected as a pilot case study to investigate the correlation between bacteria taxa and the chemical status of the river. The main physicochemical parameters, inorganic elements, organic pollutants and natural microbial community composition were assessed at four selected sites corresponding to pristine, agricultural, industrial and urban areas for three consecutive years. The overall chemical results indicated a correspondence between different groups of contaminants and the main contamination sources at the selected sampling points. Phylogenetic analysis of the microbial community analyzed by Fluorescence In Situ Hybridization method (FISH) revealed differences among the four sampling sites which could reflect an adaptive bacterial response to the different anthropogenic pressures.

Groundwater Autochthonous Microbial Communities as Tracers of Anthropogenic Pressure Impacts: Example from a Municipal Waste Treatment Plant (Latium, Italy)

“…This suggests that the additional organic carbon comes from the dump and that the microbial communities are sensitive to its origin and quality. This result, showing the negative effects on the microbial community of higher values of DOC in contaminated ecosystems, is in line with those found in in previous works [80][81][82]. Finally, it is interesting to note that in the third sampling campaign the lowest oxygen concentrations were found and the volatile organic compound 1,2 Dichloropropane detected above the legislation limits in the most vulnerable piezometers (CE-B and CE-F).…”

Point-of-Care Strategies for Detection of Waterborne Pathogens

“…The major strategies involved in nucleic acid-based detection of pathogens are hybridization and amplification. Nucleic acid hybridization involves identification of biological contaminants through complementary binding of single-stranded nucleic acid probes (labeled with radioactive or fluorescent compounds) with target organism genes [35,36]. In the presence of complementary target genes in the sample to be tested, the probe forms hydrogen bonds, facilitating its detection through autoradiography or fluorescent signals from the probe.…”

Legacy and Emerging Pollutants in an Urban River Stretch and Effects on the Bacterioplankton Community

“…A mixture of legacy and emerging pollutants has been found in rivers, causing particular concern for their possible effects on the ecosystem and human health. For example, Polycyclic Aromatic Hydrocarbons (PAHs) and some pharmaceuticals have been identified in several works as common contaminants in lotic waters [4,5]. The WFD (Water Framework Directive) commits European Union Water 2021, 13, 3402 2 of 13 member states to achieving a good qualitative and quantitative status for all water bodies [6].…”