Analysis Of Bacterial Community In Endophytic And Rhizosphere Soils Of Miscanthus And Determination Of Its Growth Promoting Characteristics

Microorganisms are closely related to plants and play an extremely important role in the ecological environment.They not only act as decomposers,but also have important functions such as material exchange,energy transfer and amino acid synthesis.In plant growth,soil nutrients are transformed into usable forms and transported to various parts of plants,thus contributing to plant growth.Promotion.Plants and microorganisms compete and interact in a long-term symbiotic process.In this process,plants also influence the composition and structure of endophytic bacteria and rhizosphere soil microorganisms,and the latter can also promote the growth of plants.In this study,the endophytic and rhizosphere soil bacteria of energy plant Miscanthus(Xiang mang1)were isolated and identified from four different media by traditional plate culture method,and their community composition was analyzed.At the same time,the identified strains were identified from the aspects of indoleacetic acid production capacity,amino acid decarboxylase capacity and phosphorus solubility,in order to determine the endophytic and root of Elymus sibiricus.The community composition and potential function of bacteria in the inter-soil,the distribution difference,regularity and potential function of bacteria in different parts of Elymus sibiricus,and the resources of endophytic and rhizosphere bacteria in Elymus sibiricus were preliminarily clarified.The main test results are as follows:(1)201 strains were isolated from the root,stem,leaf and rhizosphere soil of Miscanthus by traditional plate isolation method,and identified by 16 S r RNA gene sequence analysis.The results of homology comparison between NCBI BLAST and EZ biocloud showed that the isolated strains contained 4 phyla,7 classes,10 orders,20 families,31 genera and 68 species.Among them,Proteobacteria is the dominant phylum(45.58%).It includes 3 classes,5 orders,9 families and 15 genera,with the largest number(36.35%)and the largest species(38.23%).Bacillus,Microbacterium and Sphingomonas were the dominant genera.The number of Bacillus strains accounted for 28.35% and 94.52% of Actinobacteria.(2)The plant growth-promoting ability of 68 species of bacteria was tested.The results showed that indole acetic acid could be produced by both endophytic and rhizosphere soil bacteria,with an average of 13.06 mg/L.However,Klebsiella michiganensis(No.TG19)and Providencia rettgeri(No.LJ7)had the highest yields of indole acetic acid,reaching 61.2 and 58.6 mg/L,Klebsiella michiganensis not only produced indole acetic acid,but also showed strong ability of amino acid decarboxylase and phosphorus solubilization,with phosphorus solubility reaching 177.3 mg/L.However,there were significant differences in the ability of amino acid decarboxylase,among which the isolates from the root of Elymus sibiricus had stronger overall ability in three kinds of amino acid decarboxylase,and there was no significant difference in the ability of phosphorus solubilization among the tested strains.69% of the tested strains had phosphorus solubility between 100 mg/L and 200 mg/L.(3)Two suspected new species RS10 and RS1 were isolated from the stem of Elymus sibiricus.The two strains were further identified in terms of genetic characteristics,phenotype,physiological and biochemical characteristics and chemical characteristics.The results showed that strain RS10 was a new species of Pedobacter and RS1 was a new species of Mucilaginibacter.(1)Compared with Pedobacter kyungheensis KACC 16221(T)(97.78%)by EZ biocloud website,RS10 16 S r RNA sequence has the closest similarity,and the DNA G+C content of the strain is 39.7 mol%.Colony morphology is light yellow,round,convex bacteria,cells are rod-shaped,aerobic,motile and spore-free,with a width of 0.1~0.13?m and a length of 0.30~0.45?m;the main cellular fatty acids are iso-C15:0,iso-C17:0.-3OH and Summed Feature 3(C16:1 w7 c and C16:1 w6c);the main isoprene-like quinone is MK-7;the main polar lipids are phosphatidyl ethanolamine and aminophosphatide.The strain is named Pedobacter nanyangensis sp.Nov.(2)Compared with EZ biocloud website,RS1 16 S r RNA sequence had the closest similarity with M.kameinonensis NBRC 102645T(98.70%).The DNA G+C content of the strain was 42.80 mol%.The colony was smooth,light pink,bulging.The cell was rod-shaped,aerobic,motile-free,spore-free,0.15~0.20?m in width and 0.40~0.80?m in length.The main cell fatty acid was iso-C15:0.iso-C16:0,iso-C17:0-3OH,summed feature 3(C16:1 w7 c and iso-C15:0-2OH);the main isoprenoid quinone is MK-7;the main polar lipids are phosphatidylethanolamide,aminophosphatide,phospholipid and two unknown lipids.The strain is named Mucilaginibacter yangensis sp.nov.