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The bacteria that dominate and become enriched in the rhizosphere during continuous cropping are of increasing interest, as they can greatly adapt to the rhizosphere. However, there are still little knowledge about the general composition and function of these bacteria. In this study, we planted tomatoes in three different soils for three planting cycles and used both high-throughput sequencing and culture-dependent workflows. Despite significant differences in bacterial communities from the initial soils, we observed a similar succession in the rhizosphere bacterial community compositions. We identified certain bacteria that were gradually enriched and potentially beneficial, such as Rhizobium and Flavobacterium. However, some other potentially beneficial bacteria, such as Massilia and Lysobacter, were gradually depleted. Additionally, we found that predicted functions related to xenobiotic biodegradation, nutrient metabolism and antibiotic biosynthesis were enriched in different rhizosphere soils. Beijerinckia fluminensis GR2, which was gradually enriched in all tested soils, significantly inhibited the growth of Ralstonia solanacearum and protected the host from infection. Our study provides new insights into the assembly mechanism of gradually enriched bacteria and their role as plant-beneficial microbes that adapt well to the rhizosphere. [ABSTRACT FROM AUTHOR]

Phenolic acids are mainly released from plant residue decomposition and play important roles in the assembly of the soil microbiome. Understanding the general features of soil microbial communities modulated by phenolic acids could provide fundamental insights into the assembly of the soil microbiome. We analyzed the effects of four phenolic acids (ferulic acid, phthalic acid, salicylic acid and tannic acid) on the soil fungal communities at two concentrations. Despite the application of different phenolic acids to the soil, we were able to identify certain general changes in the fungal communities. We found that the tested phenolic acids significantly increased the deterministic assembly process of the fungal community but decreased the fungal diversity. Moreover, the fungal community structure under each tested phenolic acid treatment was distinct at low concentrations but similar at high concentrations. Salicylic acid had the greatest impacts on the fungal community. In addition, Fusarium and Aspergillus were significantly enriched in the soil amended with all the tested phenolic acids at high concentrations. Our study revealed certain general changes in the soil fungal communities modulated by phenolic acids, which deepened our understanding of the fungal assembly mechanism and provided robust insights for identifying candidate phenolic acid-degrading microbes. [ABSTRACT FROM AUTHOR]