The effects of allelochemicals from root exudates of Flaveria bidentis on two Bacillus species

Abstract

To determine the allelopathic effects of root exudates from Flaveria bidentis on function of Bacillus, pot experiment was used to collect root exudates from living plants and test its allelopathic effects on function of Bacillus frigoritolerans and Bacillus megaterium, which were two dominant bacteria in the rhizosphere soil of F. bidentis. To obtain the allelopathic substances, the root exudates were successively extracted by N-hexane, dichloromethane, ethyl acetate, and N-butanol, and their allelopathic effects were tested. The results showed that B. frigoritolerans and B. megaterium considerably increased the concentration of available phosphorus and nitrogen, respectively, when the soil was treated with different concentrations of root exudates. Among the four organic solvent extracts, dichloromethane extracts significantly increased the abundances of B. frigoritolerans and B. megaterium and promoted their nitrogen-fixing and phosphate-solubilizing abilities. Phenol was detected in dichloromethane extracts by gas chromatograph-mass spectrometer (GC-MS). Meanwhile, phenol promoted the ability to fix nitrogen of B. megaterium and its growth by increasing the soil available nitrogen concentration, but phenol promoted the ability to solubilize phosphate of B. frigoritolerans only in 0.1mg/mL concentration. Therefore, phenol was an allelochemicals in the root exudates of F. bidentis that affects the growth and activities of B. megaterium.

Effects of Septoglomus constrictum and Bacillus cereus on the competitive growth of Ageratina adenophora

“…Our study also revealed that inoculation with B. cereus weakened the positive effect of interspecific competition on A. adenophora and alleviated the negative effect on R. amethystoides growth but did not change the competitive relationship between A. adenophora and R. amethhystoides (Figure 2). We also found that B. cereus inoculation led to significantly greater promotion on R. amethystoides biomass than A. adenophora, which may be due to the different effect of root exudates from the two plants on the growth-promoting effect of Bacillus (Sun et al, 2021(Sun et al, , 2022. To understand the potential mechanisms, future studies may conduct a comparative analysis of the secondary metabolites of A. adenophora and R. amethystoides and their effect on Bacillus's ability to solubilize phosphorus and fix nitrogen.…”

“…After shaking at 180 rpm for 24 h at 37°C, the liquid was transferred into a triangular flask containing 100 mL of nutrient liquid broth medium and shaken at 180 rpm for 24 h at 37°C. The Bacillus suspension was then expanded to a concentration of 10 8 CFU/ mL (Sun et al, 2022).…”

“…The density of B. cereus in each soil sample was analyzed to investigate different treatment impacts on their growth on nutrient agar medium plates using the suspension dilution method (Yang et al, 2012;Du et al, 2020;Sun et al, 2022). Briefly, 1 g rhizosphere soil with 9 mL of sterile water was incubated at 200 r/min, heated at 90°C for 10 min, and serially diluted.…”

Beneficial rhizosphere bacteria provides active assistance in resisting Aphis gossypiis in Ageratina adenophora

“…Due to the phenotypic plasticity, compensatory or tolerance of invasive species, the negative feedback effect is significantly weakened ( Policelli et al., 2018 ). On the other hand, some rhizosphere-beneficial bacteria have a preferential impact on invasive species ( Sun et al., 2022 ). For instance, mycorrhizal fungi significantly improve the disease resistance of host plants, and the invasive plant Anthemis cotula is protected from the invasion of pests and diseases due to the high infection of arbuscular mycorrhizal fungi ( Shah et al., 2008 ).…”

“…DNA concentration was measured using NanoPhotometer N60 spectrophotometer (IMPLEN, Germany), and the PCR primers for qRT-PCR analysis (Bio-Rad CFX96 touch, Bio-Rad Laboratories Incorporated, USA) were designed based on the sequence of B. cereus strains. The specific determination method referred to the existing research ( Sun et al., 2022 ).…”