Selective Isolation Of Micromonospora And Analysis Of NAGGN Gene Clusters Releted To Salt-Tolerance

Soil salinization can lead to soil degradation and desertification,seriously affecting the sustainable development of agriculture.In order to resolve this issue,research has found that some salt tolerant or halophilic microorganisms exist in saline alkali soil,which are beneficial for plant growth.Therefore,screening related microorganisms will provide new microbial resources to solve the question of soil salinization.In this study,taken 10 soil samples from different habitats in the Tarim River Basin as materials,6 different selective culture media were used to isolate Micromonospora.After 16S r RNA gene sequencing analysis,a total of 42 species and 424 strains of Micromonospora were identified.The soil of Populus euphratica forest collected from Shaya county was the most abundant sample for the isolation of Micromonospora.1/10 ATCC 172 medium with nalidixic acid,cycloheximide,nystatin and novobiocin was the optimal medium for selective isolation of Micromonospora.The salt-tolerance of Micromonospora was screened used plate under 0%-6%salt concentration.4 strains were tolerant to 5%salt concentration,8 strains were tolerant to 3%-5%salt concentration,and 40 strains were tolerant to 0%-3%salt concentration.The whole genome scanning analysis of the NAGGN biosynthesis gene cluster of Micromonospora strains showed that 21 Micromonospora strains contained NAGGN gene clusters.Among Micromonospora containing NAGGN gene cluster,19.05%of Micromonospora could tolerance5%salt concentration,and 95.24%of Micromonospora could tolerance 3%salt concentration,indicating that there was a significant correlation between the salt tolerance of Micromonospora and NAGGN gene cluster.The fermentation products of 21 Micromonospora strains containing NAGGN gene cluster were analyzed by ~1H-NMR spectroscopy,and 10 Micromonospora species containing NAGGN gene cluster were screened to synthesize the soluble substance NAGGN inclouding M.andamanensis、M.aurantiaca、M.echinofusca、M.peucetia、M.chalcea、M.nigra、M.halophytica、M.carbonacea、M.haikouensis and M.maritima.It was found that the NAGGN gene cluster sequence in Micromonospora had species specificity,after comparing sequence alignment of the NAGGN synthase of 10 Micromonospora species.On the basis of the ~1H-NMR spectrum characteristics of NAGGN,it was found that the ~1H-NMR signal of TRM97189 was strong.Micromonospora haikouensis TRM97189 was taken as the research object,NAGGN was isolated and identified through modern chromatographic separation technology and nuclear magnetic resonance technology.Pot experiments have demonstrated that the strain TRM97189 has the ability to promote plant growth under salt stress.In order to further search for related genes involved in NAGGN synthesis,the strain TRM97189 was stressed with 0%,1%,2%and 3%salt concentrations for transcriptome sequencing analysis,the results showed that glutamine synthase was significantly upregulated along with the increasing of salt concentration,which may be involved in the biosynthesis of NAGGN.