Analysis Of The Rhizosphere Microbe Community Of The Invasive Plant Spartina Alterniflora In The Mudflats Of Beibu Gulf,Guangxi,and Identification Of Growth-promting Bacteria And Novel Species

The invasion of Spartina alterniflora has caused serious damage to coastal habitats and has severely affected local mangrove and mudflat ecosystems in Guangxi,seriously affecting the ecological environment and causing huge economic losses to the aquaculture industry.However,the diversity of the rhizosphere microbe community and the impact on the indigenous microbial community have not been reported.In this experiment,the effects of different invasive levels of Spartina alterniflora on the structure and diversity of the rhizosphere microbe community were analysed by Shotgun Metagenomic Whole Genome Sequencing method,together with soil physicochemical properties and soil enzyme activity.The bacteria were isolated from the rhizosphere soil and the roots,stems and leaves of Spartina alterniflora plants by pure culture.Functional plates and plate standoffs were used to screen for strains with pro-life and endophytic bacteria with inhibitory activity.A systematic taxonomic study of potential new taxonomic units was carried out using a multiphase taxonomy.The study provides new research ideas to study the invasion mechanism of Spartina alterniflora and provides microbial resources for subsequent agricultural applications.The key conclusions of the study are as follows:(1)The invasion of Spartina alterniflora changed the community structure and relative abundance of bacteria to a large extent.The OTUs were 58,293 and 57 for control(CK),just the invasion(JI)and successful invasion(SI),respectively.The Shannon index,Richness index and Pielou index all increased.The invasion of Spartina alterniflora CK,JI and SI resulted in 58,293 and 57 OTUs,respectively.The Shannon index,Richness index and Pielou index all increased after the invasion.The invasion of Spartina alterniflora increased the community diversity of microbe and improved the richness and evenness of the microbe community.At the class level,Alphaproteobacteria dominated in JI,and Gammaproteobacteria dominated in SI.The relative abundance of different bacterial species varied somewhat between samples,with the dominant microflora varying from sample to sample,with Vibrio and Arcobacter nitrofigilis being the dominant species in the JI and Aestuariivita boseongensis becoming the dominant species with Vibrio after in the SI.The invasion of Spartina alterniflora resulting in dynamic changes in the dominant microflora in the soil.(2)The invasion of Spartina alterniflora resulted in significant differences in the composition of microbe.PCA showed that CK,JI and SI were dispersed in distance and differed significantly in microbe composition.lef Se showed(selection of microorganisms with LDA>3.5)identified 36,17 and 21 biomarkers in the CK,JI and SI,respectively.(3)The invasion of intergrass altered soil enzyme activity and physicochemical properties.Soil phosphatase,urease and polyphenol oxidase activities increased as a result of intergrass invasion.Overall,SOC,WSOC,TP,TN,NH₄⁺-N,NO₂^--N and NO₃^--N all increased after Spartina alterniflora invasion,while PH was slightly alkaline and the difference in salinity was not significant.(4)The diversity of microbe communities in the JI was most associated with TN and NO₂^--N,the diversity of microbe communities in the SI was most associated with WSOC and soil p H,and the driving factors for the formation of the CK group were not yet determined.The dominant microflora most associated with soil TN,NO₂^--N,included Arcobacter,Phaeobacter,Erythrobacter and Amphritea.Shewanella and Pseudoalteromonas.The dominant microflora most associated with TP and soil p H are Hyphomonas and Photobacterium.The dominant microflora most associated with WSOC include Rhodococcus,Microbulbifer,Methylomarinum and Methyloceanibacter.(5)The 525 and 269 strains of bacteria were screened from rhizosphere soil and plants of different invasion levels,respectively.Based on the morphological and cultural characteristics of the colonies and the results of Rep-PCR analysis,the 141 strains and 82 strains were sequenced by 16S r RNA gene sequencing and compared with the EZbio Cloud,and were classified into 4 Phylum,6 Classes,19 Orders,35 Familiy,58 Genera and 6 Phylum,16 Orders,19 Family,31 Genera.(6)The 32 strains of nitrogen-fixing bacteria(22.70%),19 strains of phosphate-solubilizing bacteria(13.48%)and 16 strains of IAA-producing bacteria(11.35%)were obtained from the rhizosphere bacteria of H.interrogans.Screening of endophytic bacteria of F.interrogans resulted in21 strains(29.17%)of nitrogen fixing bacteria,11 strains(13.88%)of phosphate solubilizing bacteria and 22 strains(29.16%)of IAA producing bacteria.The 13 strains of endophytic bacteria with inhibitory effect on Fusarium oxysporum f.sp.cubense,the inhibition rate ranged from 15.46%to 68.31%,among which the best inhibition activity was Bacillus velezensis(68.31%),which has the potential to further develop antibacterial agents.(7)A novel species of GY10586 was screened from the rhizosphere bacteria of Bacillus interrogans and identified as a novel species of the Flexivirga using a multiphase taxonomy,named Flexivirga sp.and with the Conservation Number GY10586^T=NBRC 114183^T=MCCC 1K04991^T.