Isolation and characterization of an extremely long tail Thermus bacteriophage from Tengchong hot springs in China

Thermus strains are regarded as models to investigate the mechanism of thermostability of thermophiles, and phages from Thermus are particularly interesting because of their way to regulate gene expression. In this research, a Thermus bacteriophage named TSP4 (Thermus Siphoviridae phage) was isolated from Tengchong hot springs in China, and characteristics of morphology, temperature for phage production, pH and organic solvent sensitivity, DNA restriction endonuclease digestion and protein composition of TSP4 were further studied. TSP4 belonged to the Siphoviridae family and had a hexagonal head of 73 nm in diameter, an extremely long and flexible tail of 785 nm in length and 10 nm in width. TSP4 was very stable at 65 °C and pH 7.6. The capsid was apparently devoid of lipid. By SDS-PAGE, six protein bands were found in purified virions. Despite their exceptional habitats separated by thousands of kilometers, the characteristics of this thermophilic phage showed high similarity to Thermus siphoviruses P23-45 and P74-26 isolated from Kamchatka peninsula hot springs in the Far East, Russia.