Isolation And Characterization Of Cold-active Phages From The Glacier Of Mingyong

As a unique ecological system, low temperature and oligotrophic alpine Glacier is considered as a "living fossil" for the research of life evolution and environmental evolution on the earth, and it is also a natural microorganism "reservoir". Studies of the life and ecology in such extreme environment will be helpful to uncover the adaptation mechanisms of extremophiles in response to their living conditions and their self-evolution, which will eventually pave a new way for the development of low temperature microorganism resources for the health of human beings.In this study, classical cultivable methods of microorganisms and isolation and purification techniques of bacterial phages were used to analyze the diversity of low temperature bacteria and their phages in the samples collected from Mingyong Glaccier area located in Yunnan province and famous for its low latitude and low altitude in the world. As the results shows that197low-temperature bacterial strains belonging to more than one genus were isolated. Based on these strains,17bacteriophages were isolated and purified. Based on morphological examination, physiological and biochemical methods, biological characteristics, restriction fragment fingerprint and SDS-PAGE analysis of phage structure proteins, the17bacteriophages were further identified. They belonged to Siphoviridae, Myoviridae, Corticoviridae and Tectiviridae, respectively, and their genomes were double-stranded DNA rangded from27kb to69kb in size with different restriction fragment length polymorphisms. Results of physiological and biochemistrical characterization of the phages and SDS-PAGE analysis of phage structure proteins also demonstrated their differences. Moreover, all phage isolates exhibited characteristics of low-temperature dependence and low thermal stability. The highest temperatures for the phages to infect their hosts were lower than the maximum host growth temperatures. In addition,16S rRNA gene sequence analysis for the17host strains revealed that species of the genera Pseudomonas, Flavobacterium, Bacillus and Janthinobacterium were comparatively abundant, and the genus Pseudomonas was significantly dominant. Based on morphological, physiological characteristics and16S rRNA gene analysis, all bacterial host strains were identified. Results of growth temperature range test showed that all the strains could grow at4℃and had a wide growth temperature range, which indicated that they belong to Psychrotrophs. Furthermore, the results also showed that all the host strains were gram negative bacteria with rod-shaped cells. Most of the hosts produced pigments.This study primarily revealed the diversity of low temperature bacteria and bacteriophages in Mingyong Glaccier area, and many valuable cold-adapted microorganisms were also isolated, which provide a basis for the future research and applications.