Morphological and phylogenic diversity of cyanobacterial populations in six hot springs of Thailand

Abstract

To characterize the phylogenetic and morphological diversity of cyanobacteria in Thailand, cyanobacteria were collected from mats in six hot springs with water temperatures ranging from 40 to 75 °C. Samples were collected for culture isolation, microscopic morphological examination, and molecular analysis of the 16S rRNA sequence to establish the levels of morphological versus genomic diversity. Fourteen cyanobacterial morphotypes were investigated using microscopy with the dominant species of cyanobacteria being Synechococcus spp., Phormidium cf. boryanum and Leptolyngbya spp. A total of 20 distinct isolates of cyanobacteria were grown in culture medium, and an additional 79 samples were examined using denaturing gradient gel electrophoresis and DNA sequence analysis to establish phylogenetic relationships. The observed decrease in morphological diversity with increasing water temperature was found to be compensated for by an increase in molecular sequence diversity of the morphologically indistinguishable cyanobacterial species. Molecular clines were found to span both temperature and geophysical boundaries for samples from the northern and southern Thailand regions.