engleski

Microbial mats in intermittent freshwater karstic spring

Live samples of microbial mat community, together with main ecological parameters, were taken during winter 2013 and spring 2014 in Krčić Spring. Diatoms were counted and identified using scanning electron microscopy (SEM). After DNA isolation of cyanobacterial species, PCR (polymerase chain reaction) was used for the amplification of cyanobacterial 16S rRNA fragments to obtain pure clonal sequences for each sample. The resulting sequences were compared to the database (GenBank) and based on the similarity phylogenetic trees were constructed. The sequences showed high homology (98‐99%) with the 16S rRNA gene of the Oscillatoriales (genera Tychonema, Pseudoanabaena, Hydrocoleum, Wilmottia and Phormidium autumnale). Sequences grouped into 2 separate clusters: (i) "Phormidium", and (ii) "Wilmottia". Sequence comparison showed that there was 7‐10% difference in 16S rRNA among the two clusters presented. The results indicate a distinct phylogenetic separation between the "Phormidium" and "Wilmottia" clusters. Furthermore, "Wilmottia" cluster originated exclusively from the sample collected in winter and showed 99% homology to Wilmottia sp. CAWBG522 isolate from New Zealand. Despite very high homology, sequences formed distinct sub‐ clusters inside "Phormidium" and "Wilmottia" cluster with spring clones being further separated from winter ones, which indicates that cyanobacteria from the karstic Krčić Spring represent genotypes specific for the Croatian region.

microbial mat; karstic spring; Phormidium

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