A molecular approach for the impact assessment of fecal pollution in river ecosystems

Abstract

Microbiological indicators such as Escherichia coli and Enterococci are commonly used to detect fecal pollution and presence of other pathogens, in the monitoring programs of sanitary surveillance of freshwater ecosystems. Clostridium perfringens (spores) is suggested as an alternative fecal indicator, it provides evidence of historical fecal contamination. This work aims at assessing the genetic variability of the anaerobic microbial community in river sediments and its relation to different fecal pollution sources. This can be obtained through a combined approach involving microbiological and molecular (16S rRNA) tools of isolated bacteria. The study was conducted on the river systems Foglia, Tevere, Astura, and Sitzerri located in three Italian regions. The frequencies of observed haplotypes proved to be remarkably different in the four sampling areas. The phylogenetic relationships among the species obtained from the comparison of the different genetic sequences made it possible to identify six homogeneous clusters, among which, five were attributed to the genus Clostridium and one to the genus Bacillus. The results of this study suggest a possible relation between different typologies of impacts and the presence of particular species of anaerobes. The research for sulfite reducing clostridia in river sediments could therefore have an essential role in the query for complete information on the quality state of river ecosystems.