Antibacterial Activity Study Of Endophytic And Rhizospheric Actinomycetes From Two Plants And Taxonomic Dentification Of Spirillospora Tritici

Actinomycetes are not only an important part of the soil ecosystem,but also an important source of various natural products of medicinal value.The variety of actinomycetes in the root and rhizosphere of plants is more complex because of the influence of plant and root microbes.Endophytic actinomycetes and rhizosphere actinomycetes not only help plants resist harm when the plants are attacked by pathogens,but also produce biologically active substances to help plants from attack by pathogens.In the new century,obtaining new active compounds from actinomycetes or finding suitable microbial agents to help plants to fight diseases and insect pests and improve the yield and quality of agricultural products is a hot topic.Based on the particularity of the living environment in plant root and Rhizosphere actinomycetes,many researchers began to use it as a source of isolation of active actinomycetes.Selecting the traditional medicinal plant Banxia and the striped rust wheat variety taichun29 as experimental materials,exploring endophytic actinomycetes and rhizosphere actinomycetes of the two plants,to discover new bioactive substances and novel species.Five screening media were used in this experiment.A total of 168 actinomycetes were isolated.Thirty-three strains from endosphere and sixty-four strains from rhizobacterial of Banxia plants,seventeen strains from endosphere and fifty-four strains from rhizobacterial of wheat.One pathogenic bacteria and thirteen pathogenic fungi were used as target bacteria to study the activity of these actinomycetes.The results showed that there were twenty-three strains of Actinomycetes with biological activity.There are seventeen strains could inhibit the growth of three kinds of pathogenic bacteria,ten strains could inhibit the growth of five pathogenic bacteria,six strains can inhibit the growth of more than ten pathogens,four strains of bacteria have an antimicrobial diameter more than 18 mm against the Fusarium oxysporum,Elsinoe fewcetti,Alternaria mali Roberts and Sclerotinia sclerotiorum(Lib.)de Bary respectively,one strain not only has inhibitory effects on twelve pathogens,but also has more than20 mm in diameter against six of the pathogens.In addition,there is a strain that has a significant inhibitory effect on all tested strains(including bacteria and fungi),Two suitable BXT54 fermented liquid culture media(Medium 2 and PTM)were selected and the stability of the active compounds produced by fermentation was explored.The results showed that the active substance had certain high temperature resistance and acid and alkali resistance.This also provides a certain theoretical basis for the separation and purification of metabolites and the identification of compound structures.Observe the morphological characteristics of the isolated strain on the medium,analysis of 16S rRNA results on the EzBioCloud website and selection of strain SJ 21 for polyphasic approach.EzTaxon-e analysis of the 16S rRNA gene sequence revealed that strain SJ 21 belongs to the genus Spirillospora and was most closely related to Spirillospora albida IFO 12248~T(98.75%16S rRNA gene sequence similarity),Actinomadura montaniterrae JCM 16995~T(98.68%),Actinomadura fibrosa ATCC49459~T(98.53%)and Actinomadura nitritigenes DSM 44137~T(98.38%).using some phenotypic characteristics,chemotaxonomic characteristics and DNA–DNA hybridization experiment evident strain SJ 21 should represent a novel species of the genus Spirillospora,for which the name Spirillospora tritici sp.nov.is proposed.The determination of the Spirillospora tritici genome framework and the prediction of the secondary metabolite gene cluster provide an important information basis for the study of the taxonomic status of the strain Spirillospora tritici in the genus spirospora and the prediction of secondary metabolites.