Abstract

RAMIREZ-MORENO, Sergio; MARTINEZ-ALONSO, Maira; MENDEZ-ALVAREZ, Sebastián  and  GAJU, Núria. Seasonal microbial ribotype shifts in the sulfurous karstic lakes Cisó and Vilar, in northeastern Spain. INT. MICROBIOL. [online]. 2005, vol.8, n.4, pp.235-242. ISSN 1139-6709.

Spatio-temporal changes in two sulfurous lakes from the karstic area of Banyoles (Girona, Spain), holomictic lake Cisó and meromictic lake Vilar, were studied over one year. Samples were collected at different depths from the two lakes on the same days, during each of the four seasons, and several physico-chemical variables (temperature, light, pH, conductivity, sulfide, oxygen concentration, pigment concentrations, etc.) were measured. To fingerprint bacterial populations from each sample, DNA was extracted, bacterial 16S rRNA genes were amplified by PCR, and restriction fragment length polymorphism (RFLP) analyses of the total bacterial 16S rDNAs were performed. Each 16S rDNA pool was independently digested with three restriction endonucleases (AluI, HinfI, and RsaI) and separated electrophoretically. More restriction fragments were obtained from the Lake Vilar samples than from the Lake Cisó samples. Moreover, intrasample and intersample differences were observed in each lake. RFLP patterns were compared by scoring similarities using the Jaccard coefficient and then building a multidimensional scaling (MDS) map from the resulting similarities matrix. In both lakes, results indicated that seasonality was mostly responsible for the observed fluctuations in the RFLP patterns, while the effect of stratification was less pronounced.

Keywords : Domain Bacteria; sulfurous lakes; seasonal shift; 16S rRNA genes; restriction fragment length polymorphism (RFLP); multidimensional scaling (MDS).

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