| Previous studies have found that myxobacteria were the species-specific microbe in the rhizosphere of allelopathic rice,which might imply the myxobacteria was the important factor in the process of the rhizobiological properties of the rice allelopathic potential.So this study aims to isolate and purify myxobacteria in the rhizosphere of allelpathic rice and identify the weed-suppression potential,and and evaluate the effect of rice allelochemicals phenolic acids on the proliferation of myxobacteria,and analysis the bioactive metabolisms and proteins that myxobacteria strains produce or exudates by the technology of GC-MS and proteomics in this work.The primary results are shown below:The 4 strains that belongs to Myxococcus spp.were separated from the rhizosphere of allelopathic rice by using rabbit dung-induced,yeast-induced and filter-induced methods,the 4 strains were Myxocuccus fulvus,Myxococcus stipitatus,Coralloccus macrosporus and Myxococcus xanthus,based on the result of 16S rDNA phylogenetic tree,Myxocuccus fulvus?Myxococcus stipitatus were found more closer.The 4 strains were subsequently employed to identify the weed-suppression potential on the barnygrass,the results showed that all of the 4 strains could significantly inhibit the germination of the seeds and stem growth of barnyardgrass.In the inhibition of stem-grow,the Myxocuccus.fulvus and Myxococcus stipitatus presented higher inhibition ratios(50%)than the other two strains(30%).However,the germination-inhibition effect of Myxococcus xanthus was significantly improved when it grows in the culture including ferulic acid,which may indicate ferulic acid can induce the enhancement of the ability of Myxococcus xanthus in weed-suppression.To discuss How phenolic acids affect the myxobacteria,the preliminarily effects of myxobacteria induced by phenolic acid were studied in vivo.Four kinds of phenolic acids allelochemicals,including p-hydroxybenzonic acid,cinnamic acid,vanillic acid,and ferulic acid were used to evaluate this preliminarily effects.The results showed that ferulic acid has the lowest concentration(0.05mM)threshold which can induce the growth of modal strains Myxococcus xanthus.Howerer,ferulic acid has no induction effect on the preliminarily of Myxococcus stipitatus,which implys the intraction between the root exudates of the plant and the particular microbe of rhizosphere may be species-specific.To reveal the relation between phenolic acid and myxobacteria,and the functional proteins related gowth of myxobacteria.This paper explored the expression model of metabolites and proteins in the induction of ferulic acid by the technologies of GC-MS and proteomics.The results showed that there was obvious differences in the species and quantity of the metabolites between the control and the ferulic acid-induced myxobacteria.Various bioactive secondary metabolites were exudated by Myxococcus xanthus under the induction of ferulic acid,and the metabolites function in inhibited DNA or RNA synthesis,DNA topoisomerase,and so on,which may be contribute to improve weed-suppression of myxobacteria.Ferulic acid increased the protein expression folds of regulatory factors and recognition receptors in Myxococcus xanthus,the up-regulated signal pathway arrelative proteins suggested that ferulic acid may act as a signal molecular in the interaction between Myxobacteria cells;and non-ribosomal peptide synthase,polyketide synthase type I which benefit to the production of secondary metabolites were also up-regulated,this result agrees with the GC-MS.In summary,the study suggests that myxobacteria from allelopathic rice rhizosphere have weed-supression ability,and ferulic acid can enhance this effect of Myxococcus xanthus,the increased secondary metabolites of myxobacteria under the induction of ferulic acid may contribute to the increasement of the weed-inhibition.And the results offer theoretical basis for exploring allelopathic myxobacteria and the bioactive secondary metabolites in the future. |
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