Fingerprinting Chamaesiphon populations as an approach to assess the quality of running waters

Abstract

Cyanobacterial communities are highly diverse in freshwaters and respond rapidly to changing environments. Previous studies have highlighted variations in the structure and composition of epilithic cyanobacterial communities in response to eutrophication in watercourses. In the present study, changes in benthic cyanobacterial communities from Guadalix River (Spain) biofilms were examined using temperature-gradient gel electrophoresis (TGGE) in conjunction with microscopic examination of field-fixed samples, focusing on populations of one of the dominant cyanobacteria:Chamaesiphon. Environmental characteristics were determined in order to characterize the trophic status of the sampling sites. The presence of cyanobacteria in the river was determined from complex TGGE patterns, band extraction, and subsequent sequencing of 16S rDNA gene fragments. The microscopic observations revealed that the unicellular genus Chamaesiphon and the filamentous genus Phormidium were dominant in the studied locations. Within the 2 genera, 4 Chamaesiphon populations were identified (Chamaesiphon fuscus, Chamaesiphon starmachii, Chamaesiphon subglobosus, and Chamaesiphon polymorphus) and Phormidium was represented at the sampling sites by the Phormidium autumnale morphotype. TGGE banding patterns differed among samplings sites as a function of water quality. The genetic analysis revealed 4 phylotypes within the genus Chamaesiphon and 1 phylotype within the classic P. autumnale clade. Chamaesiphon phylotypes were not equally distributed in all the sampling locations. Some phylotypes were related to low nutrient concentrations, while others were associated with eutrophic conditions. Our results support the use of fingerprints of Chamaesiphon populations obtained by TGGE to examine changes in water quality.