Isolation of Thermotoga spp. and Fervidobacterium spp., and Characterization of 16S rRNA Genes of Order Thermotogales: Unique Lineage of Hyperthermophiles Thriving in 3 Hot Springs in Thailand

Porranee Keawram, Veeranun Pongsapukdee, Wirojne Kanoksilapatham


Order Thermotogales comprise mostly strictly anaerobic thermophilic and hyperthermophilic bacteria which thrive
in high temperature habitats throughout the world. In order to study diversity of hyperthermophiles in Thailand’s hot
springs, culture dependent technique was performed at 80 oC. Pure cultures of 19 isolates obtained from 3 hot springs
were characterized based on 16S rRNA genes of order Thermotogales. Twelve and 7 isolates were identified as deepest
blanches within two clades formed by divergent encapsulated rod shaped bacteria belonging to Fervidobacterium and
Thermotoga, respectively. Phylogenetic evidences suggest that the Thailand strains from both branches are possible
candidates for two novel species. Closely related strains within both genera were identified regardless of their habitats
and years of sample collection, implying that these native inhabitants found in Thailand’s hot springs might have
evolved from a unique common ancestor. Because all isolates require extremely high temperatures for growth, these
isolates are likely sources of genes encoding numerous thermostable enzymes.

Key Words: Fervidobacterium; Hot spring; Hyperthermophile; Thermotoga; Thermotogales

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