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Soilborne pathogens affect plant growth and food production worldwide. The application of chemical fertilizers and pesticides to control plant diseases has harmful effects; fortunately, plant growth-promoting rhizobacteria can be used as a potential alternative strategy. Here, Paenibacillus jamilae HS-26 was selected for its highly antagonistic activity against several soilborne pathogens. The bacterium synthesized hydrolytic enzymes and released extracellular antifungal metabolites and volatile organic compounds—primarily, N, N-diethyl-1, 4-phenylenediamine, which was detected by gas chromatography-mass spectrometry and shown to inhibit fungal mycelial growth. Furthermore, HS-26 was useful for nitrogen fixation, phosphate and potassium solubilization, and siderophore and indoleacetic acid production. In vitro tests and pot experiments revealed that HS-26 considerably increased plant biometric parameters. Illumina MiSeq sequencing data showed a significant reduction in soilborne pathogens and increase in beneficial bacteria in the wheat rhizosphere after treatment with strain HS-26.

Aims We aimed to develop a biological agent that regulates the microbial community structure of the poplar rhizosphere and alleviates the effects of continuous poplar cropping. Methods and Results Poplar rhizosphere soils were treated with or without Paenibacillus polymyxa CP-S316 microbial fermentation medium. Real-time polymerase chain reaction was performed to measure bacteria and fungi in both groups, and microbial communities were analysed by metabarcoding. In fungi, the operational taxonomic units, abundance-based coverage estimator and Chao index of the CP-S316-treated group were significantly lower than those in the control check (CK) group. In bacteria, the proportions of Bacillus in the CP-S316 and CK groups were 5·20 and 2·38%, respectively, whereas those of Rhizoctonia were 2·20 and 5·82% respectively. The diameter at breast height, culturable bacteria and total bacteria of poplars treated with CP-S316 exceeded those in the CK group. Conclusions Our data confirmed that CP-S316 could improve the microbial community structure of poplar rhizosphere and promote the growth of poplars. Significance and Impact of the Study Research aimed at alleviating continuous cropping obstacles and promoting poplar growth via biocontrol agents is uncommon. We analysed the community structures of bacteria and fungi in rhizosphere soil to illustrate the use of CP-S316 for poplar cropping for improving plant health in the continuous cropping of poplar trees.

Rhizospheric microorganisms can increase phosphorus availability in the soil. In this regard, the ability of phosphofungi to dissolve insoluble phosphorus compounds is greater than that of phosphate-solubilizing bacteria. The aim of the current study was to identify efficient phosphofungi that could be developed as commercial microbial agents. Among several phosphate-solubilizing fungal isolates screened, strain CS-1 showed the highest phosphorus-solubilization ability. Based on phylogenetic analysis of the internal transcribed spacer region sequence, it was identified as Aspergillus niger. High-performance liquid chromatography analysis revealed that the mechanism of phosphorus solubilization by CS-1 involved the synthesis and secretion of organic acids, mainly oxalic, tartaric, and citric acids. Furthermore, strain CS-1 exhibited other growth-promoting abilities, including efficient potassium release and degradation of crop straw cellulose. These properties help to returning crop residues to the soil, thereby increasing nutrient availability and sustaining organic matter concentration therein. A pot experiment revealed that CS-1 apparently increased the assessed biometric parameters of wheat seedlings, implying the potential of this strain to be developed as a commercial microbial agent. We used Illumina MiSeq sequencing to investigate the microbial community composition in the rhizosphere of uninoculated wheat plants and wheat plants inoculated with the CS-1 strain to obtain insight into the effect of the CS-1 strain inoculation. The data clearly demonstrated that CS-1 significantly reduced the content of pathogenic fungi, including Gibberella, Fusarium, Monographella, Bipolaris, and Volutella, which cause soil-borne diseases in various crops. Strain CS-1 may hence be developed into a microbial agent for plant growth improvement. Electronic supplementary material The online version of this article (10.1186/s13568-018-0593-4) contains supplementary material, which is available to authorized users.

The establishment of safe and effective methods for controlling fungal disease is an urgent issue in agriculture and forestry. Microbiological control of plant disease is expected to achieve better results than use of chemically derived fungicides. This study aimed to establish Brevibacillus laterosporus JX-5 as a potential microbiological control agent of poplar canker. The bacterium was isolated from the poplar rhizosphere and demonstrated significant growth inhibition of several pathogenic fungi in vitro. The antifungal components of Br. laterosporus JX-5 were isolated and identified. The fermentation broth of Br. laterosporus JX-5 and its main antifungal component, designated as component B, reduced Botryosphaeria dothidea associated canker of the excised poplar branch by 70 and 90%, respectively. Component B is considerably heat-stable, adaptable to a broad pH range, and UV-resistant. It could inhibit Bo. dothidea by permeating the fungal membrane, fracturing the nuclei, damaging the cell wall, and eventually killing the pathogenic fungus. The antifungal activity exhibited by Br. laterosporus JX-5 and its bioactive metabolic products indicate its feasibility as a potential biocontrol agent for plant diseases.

Antimicrobial peptides are promising anti-infective agent candidates because they have a broad antimicrobial spectrum and bioactivity and are unlikely to elicit antibiotic resistance. The bogorols represent a new cationic antibiotic peptide and possess great therapeutic potential because of their bioactivity and precise mode of action. Here, we report that Bogorol B-JX (BBJX), a peptide previously isolated from Brevibacillus laterosporus JX-5 by us, has significant antibacterial and antitumor activities in vitro. BBJX was found to inhibit methicillin-resistant Staphylococcus aureus (MRSA) at 2.5 µg/mL with distinct mechanisms of action from those against Bacillus bombyseptieus and Escherichia coli. It penetrates MRSA membrane with little visible destruction and binds to genomic DNA. BBJX could inhibit the proliferation of human histiocytic lymphoma cell line U-937 and ConA-activated spleen cells at 5 µg/mL, but was not cytotoxic to the Jurkat cells, resting spleen cells or differentiated macrophage-like U-937 immunocytes. Moreover, BBJX caused apoptosis of U-937 cells by opening the mitochondrial permeability transition pore and stimulating the production of reactive oxygen species. Taken together, these studies provided basis for future medical application of the bogorols.

Plant growth promoting rhizobacteria (PGPR) for perennial apple trees (PAT) and apple tree saplings under continuous cropping (ATS) from two places in China were isolated and analyzed, and cluster analysis of BOX-PCR data was performed. The results showed that the quantities of both total rhizobacteria and the four kinds of PGPR (nitrogen-fixing bacteria, phosphate-solubilizing bacteria, silicate bacteria and antagonistic bacteria) from PAT were higher than those of ATS at different sampling points. The largest dissimilitude of BOX-PCR patterns for the PGPR indicated the genetic evolutionary distance of bacteria isolates was closer for the same sampling point. The shared cluster groups of the same variety of PGPR from two kinds of apple rhizosphere or different sampling points were very few. The diversity index, richness index and evenness index of PGPR from PAT were higher than those of ATS at both sampling points, while the dominance index was lower. The amounts and varieties of PGPR significantly changed between the PAT and ATS from different areas, which indicated the PGPR of the same plant varied from place to place due to the different environmental conditions. These results indicate that PGPR from PAT have the advantage of species diversity compared with ATS.

Fungi are important soil components as both decomposers and plant symbionts and play a major role in ecological and biogeochemical processes. However, little is known about the richness and structure of fungal communities. DNA sequencing technologies allow for the direct estimation of microbial community diversity, avoiding culture-based biases. We therefore used 454 pyrosequencing to investigate the fungal communities in the rhizosphere of Xinjiang jujube. We obtained no less than 40,488 internal transcribed spacer (ITS) rDNA reads, the number of each sample was 6943, 6647, 6584, 6550, 6860, and 6904, and we used bioinformatics and multivariate statistics to analyze the results. The index of diversity showed greater richness in the rhizosphere fungal community of a 3-year-old jujube than in that of an 8-year-old jujube. Most operational taxonomic units belonged to Ascomycota, and taxonomic analyses identified Hypocreales as the dominant fungal order. Our results demonstrated that the fungal orders are present in different proportions in different sampling areas. Redundancy analysis (RDA) revealed a significant correlation between soil properties and the abundance of fungal phyla. Our results indicated lower fungal diversity in the rhizosphere of Xinjiang jujube than that reported in other studies, and we hope our findings provide a reference for future research.