Enrichment and Phylogenetic Analysis of Moderately Thermophilic Myxobacteria from Hot Springs in Japan

Abstract

During the search for thermophilic myxobacteria in geothermal environments, four myxobacteria-like cultures that grew at temperatures of up to 50°C and optimally at 45–49°C were enriched from various hot springs in Japan. Three of the cultures were derived from freshwater hot springs and one from a coastal saline spring. Although all lacked fruiting structures, they were bacteriolytic and formed diffusive shallow crater-like colonies. Even after repeated enrichment procedures using Escherichia coli-prey agar media, the crater-like cultures were usually surrounded by thin, film-like, spreading colonies of other gliding bacteria that grew faster. Within the crater-like sunken area, rod-shaped bacterial cells were observed. 16S rRNA gene sequences from the myxobacterial cultures were amplified by nested PCR with myxobacteria-specific primers, subcloned, and phylogenetically analyzed. All of the myxobacterial clones obtained from the three cultures were assigned to the suborder Sorangineae. These clones were distantly positioned within this suborder, and mostly shown to represent new genera of myxobacteria. These results suggested that diverse species of moderately thermophilic myxobacteria, including many as yet undescribed, ubiquitously inhabit hot spring environments.