Biodiversity Of Halophilic Archaea Isolated From Gaize Salt Lake In Tibet And Formation Of Liposomes From Polar Lipids Of Haloarchaea

The hypersaline environments are important extreme environments on the earth.The hypersaline environments mainly include salt lakes,artificial solar salterns and salt mines.These environments contain abundant halophilic archaea resources.Halophilic archaea have unique physiological characteristics,genetic characteristics and evolutionary strategies,so they are worthy of digging and researching.There are many salt lakes in China,mainly distributed in the northwest region.The high altitude,low dissolved oxygen,and high radiation environment in Tibet may have given birth to a unique and diverse halophilic archaea.Therefore,soil samples from salt lake in the Gaize County of Tibet were collected,halophilic archaea strains were isolated and purified,the diversity of halophilic archaea was clarified,potential new taxa were identified,and halophilic archaea strains containing different polar lipid components were screened.At last,halophilic archaeal liposomes were prepared,characterized,and the stability was characterized.Eighty-eight halophilic archaea were isolated from the salt lake sample from the Gaize County.The phylogenetic analysis based on 16S rRNA gene showed that these88 strains belong to 15 species under 11 taxa,of which 8 halophilic archaea strains,AGai3-2,AGai3-5,Gai3-17,Gai1-5,Gai1-3,Gai3-2,Gai3-78 and Gai4-2,belong to new taxa.The results of polyphasic taxonomy indicate that strain AGai3-2 reprsents a new species of a novel genus,and strain Gai1-5 represents a new species of Haloprofundus,and strain Gai3-17 represents a new species of Halobacterium.The names,Salinicalculus salinus AGai3-2~T,Haloprofundus salinus Gai1-5~T and Halobacterium rutilum Gai3-17~T,are proposed.The halophilic archaeal phospholipid bimolecules are different from bacteria and eukaryotes,resulting in the advantages of halophilic archaeon liposomes in terms of stability and adjuvant.In this paper,halophilic archaeon liposomes were prepared by thin-film dispersion method using three halophilic archaeal phospholipid dimers with different polar lipid components.The particle size,Zeta potential and dispersion coefficient were characterized and compared with traditional liposomes.The stability at different pH values was compared.The results showed that the average particle sizes of the halophilic archaeal liposomes were larger than that of conventional liposomes,and their surfaces were negatively charged.In vitro,the size of Halorubrum aidingense liposomes did not change significantly under p H 2,pH 5,pH7,and pH 9,suggesting its stability at different p H values.The study may provide a theoretical basis for the further application of halophilic archaeal liposomes.