Faecal indicator bacteria in river biofilms.

Area of Science:

• Environmental microbiology
• Water quality monitoring
• Riverine ecosystems

Background:

• Surface water biofilms are primarily composed of non-native microorganisms.
• Pollution introduces fecal bacteria that can interact with these biofilms.
• Fecal indicators like total coliforms, E. coli, and enterococci signal fecal contamination and potential pathogen presence.

Purpose of the Study:

• To investigate the occurrence of fecal indicator bacteria in German river biofilms (epilithic biofilms and sediments).
• To assess the survival and potential role of these bacteria within biofilm communities.

Main Methods:

• Sampling of epilithic biofilms and sediments from German rivers.
• Quantification of total coliforms, E. coli, and intestinal enterococci.
• Comparison of bacterial concentrations in biofilms versus overlying water.
• Identification of coliform and enterococcal isolates to determine species present.

Main Results:

• All investigated biofilms contained significant concentrations of fecal indicator bacteria.
• Fecal indicator bacteria represented a minor fraction of the total biofilm community.
• Biofilms showed approximately 100-fold higher concentrations of fecal indicators compared to the overlying water.
• Identified isolates included opportunistic pathogens.

Conclusions:

• Fecal indicator bacteria can survive in river biofilms alongside high densities of native microflora.
• River biofilms may serve as reservoirs for bacterial pathogens in polluted aquatic environments.
• This highlights the importance of biofilms in understanding pathogen dynamics in rivers.