Abstract: Three cold-active bacteriophages infected Pseudomonas named MuztagBP1,MuztagBP2,and MYBP2A-15 were isolated from Karakul Lake of East Pamir and Mingyong glacier,and their biological characteristics were studied. All the phages cultured by double-layer agar method were characterized by observing the shape of plaque,and the morphologies of plaque particles were observed by the electron microscopic after negative staining of phosphotungstic acid. The physiological characteristics of 3 phages such as the proliferation temperature,the stability to heat and pH,the sensitivity to chemical reagent,and the one-step growth curves were compared and analyzed. The results indicated that the morphologies and biological characteristics differed significantly though the host of 3 phages belonged to the same genus of Pseudomonas. Three phages were in the same type with the structure of head to tail. Among them,both MuztagBP1 and MYBP2A-15 had an isometric head（about 68 nm and 74 nm in diameter）with a contractile tail（about 130 nm and 160 nm in length respectively）;and they were identified as the family of Myoviridae. While MuztagBP2 belonged to the family of Siphoviridae that had a long tail（about 640 nm in length）. All the phages presented thermolability and UV resistance. MuztagBP1 was extremely sensitive to chloroform,isopropyl alcohol and ether,which indicated that MuztagBP1 was a cold-active phage with a lipid envelope,while MuztagBP2 and MYBP2A-15 were not so. The one-step growth curves demonstrated that the latent period,burst period,and burst size of 3 phages were different.

Key words: Karakul Lake, Pseudomonas, cold-active bacteriophages