|其他摘要||Halophyte is regarded as suitable tool for the rehabilitation of saline soils. Exploiting the halophyte associated endophytic bacteria may aid in phytoremediation of saline soils. However, little is known about the diversity of endophytic bacterial communities in halophytes. Therefore, in this study, different species of halophytes grow in the same saline habitat and the same species of halophyte grow in different saline environment were selected, by using 454 pyrosequencing techniques and traditional culture methods, for the first time, the distribution of endophytic bacterial communities among different halophytes and different saline habitats were analyzed, and the functions of isolates were determined. Moreover, a novel species were classified. The major results are as follows:
(1) Pyrosequencing results indicated that halophytes in the northern region of Xinjiang harbored diverse endophytic bacteria. Endophytic bacterial communities in the 16 plant species mainly included four phyla, which were Proteobacteria, Tenericutes, Actinobacteria and Firmicutes. Major class for Proteobacteria, Tenericutes, Actinobacteria and Firmicutes were Gammaproteobacteria, Mollicutes, Actinobacteria and Bacilli respectively.
(2) In terms of plant species classification, colonial differences existed among plant species at perspectives of composition of bacterial taxa. Taking Tamarix ramosissima, Tamarix hispida, Reaumuria soongorica as example, endophytic bacterial communities in the three plant species were less diversified than these in other plant species; in the case of plant genus level, endophytic bacteria in different plant species but belonging to same plant genus exhibited similarity; as to plant family level, Actinobacteria and Proteobacteria comprised the main abundant phyla in the halophytes belonging to Chenopodiaceae; Proteobacteria comprised the main abundant phylum in the halophytes belonging to Zygophyllaceae; Tenericutes comprised the main abundant phylum in the halophytes belonging to Tamaricaceae; Proteobacteria, Fimicutes and Actinobacteria comprised the main abundant phyla in the halophytes belonging to Plumbaginaceae.
(3) The analysis to distribution of endophytic bacteria in halophyte Salicornia europaea showed obvious dynamic changes. The host growth stages and growth habitat determined the endophytic bacterial communities. It has been indicated that the dominant endophytic bacteria during different growth periods in Fukang was related to Pseudomonas, which in Karamay were related to Pseudomonas and Delftia, Kushneria, Serratia and Pantoea, Pantoea, Erwinia, respectively.
(4) Using a culture-dependent approach, 186 bacterial strains were isolated on agar. 16S rRNA sequences comparison exhibited that isolates distributed in 4 phyla, and 103 species. These isolates were tested for salt tolerance and plant growth-promoting traits. Two strains with nitrogen fixation ability, 57 strains with phosphate solubilisation ability, 25 strains with siderophore production ability, 13 strains can produce indole acetic acid, 9 strains with 1-aminocyclopropane-1-carboxylic acid deaminase activity, 16 strains can produce protease, 2 strains can produce lipase, 53 strains can produce cellulase. Plant growth-promoting activities were tested in axenically grown S. europaea seedlings at different NaCl concentrations (0.05–0.5 mol L−1). For Variovorax paradoxus XJB-YJ2, Bacillus endophyticus XJB-YJ4, Arthrobacter agilis XJB-YJ21, Bacillus tequilensis YJ-S4 and Planococcus rifietoensis YJ-ST4, significant plant growth-promoting activities were observed in Salicornia europaea under salt-stress conditions.
(5) Strain EGI 60002T, was isolated from the halophyte Suaeda physophora. On the basis of morphological, physiological, chemotaxonomic data, and phylogenetic analysis, strain EGI 60002T has been classified as a novel species within the genus Actinotalea, for which the name Actinotalea suaedae sp. nov. is proposed.|