| Continuous cropping obstacles are one of the most important agroecological problems in modern agricultural production.Accumulation of Ferulic acid(FA)is one of the main reasons of continuous cropping obstacle.Many reports have shown that Sphingomonas has unique abilities in promoting plant growth and degrading aromatic compounds.In this paper,the characteristics and pathways of degradation of ferulic acid by Sphingomonas XS-10T were studied.Cucumber,a ferulic acid sensitive plant,was used to evaluate the restoration effect of strain XS-10T in ferulic acid-accumulating soil.The main results are as follows:(1)Strain XS-10T could utilize ferulic acid as the sole carbon source.The optimal conditions for the degradation of ferulic acid by strain XS-10T were as follows:temperature 35?,salinity 0%,and p H 7.0;The growth and degradation of ferulic acid by strain XS-10T were completely inhibited by 400 mg·L-1 ferulic acid.The growth and degradation of ferulic acid by strain under ammonium nitrogen condition were better than that under organic nitrogen or nitrate nitrogen.The strain could degrade the other phenolic acid compounds,such as vanillin,vanillic acid,and syruvic acid.(2)Genomic analysis revealed that strain XS-10T degrades ferulic acid through the Co A-non-?-oxidation pathway and the protocatechuic acid-4,5-cleavage pathway.First,ferulic acid is transferred to ferulic-Co A by acetyl-Co A ligase,and then vanillin is generated by p-hydroxycinnamyl Co A hydrase.Further,vanillic acid is generated catalyzed by aldehyde dehydrogenase.Under the catalysis of protocatechuic acid-4,5-lyase,the aromatic ring was opened,and then entered the tricarboxylic acid cycle through multi-step reaction to realize the complete degradation of ferulic acid.In addition,vanillic acid and protocatechuic acid were detected by LC-MS.(3)Strain XS-10Tcould produce ammonia and siderophore;strain XS-10Tcould degrade 18.8%of ferulic acid in soil within 3 days;strain XS-10T could promote the growth of cucumber.Inoculating strain XS-10T into the ferulic acid-contaminating soil reduced the activities of superoxide dismutase(SOD)and peroxidase(POD)in cucumber leaves,and increased the activities of phenylalanine aminotransferase(PAL)and catalase(CAT),alleviated the inhibition of ferulic acid on cucumber seedling growth,but had no significant change in soil physical and chemical properties;In addition,strain XS-10T and ferulic acid in the soil will change the richness and diversity of soil bacteria,and change the species composition of soil bacteria. |
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