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Schematic representation of secondary metabolite gene clusters in Bacillus amyloliquefaciens SQR9. Gene clusters encoding non-ribosomal peptide synthetases (NRPSs). The names assigned to individual genes in SQR9 are indicated above the arrows. Products assigned to the respective pathways are shown on the right. GenBank accession numbers in the SQR9 genome are indicated below the arrows.
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Bacillus amyloliquefaciens SQR9 exhibited predominantly antagonistic activities against a broad range of soilborne pathogens. The fungi-induced SQR9 extracts possess stronger antifungal activities compared with SQR9 monoculture extracts. To investigate how SQR9 fine-tunes lipopeptides (LPs) and a siderophore bacillibactin production to control diff...
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... previous research detected the LPs and the siderophore bacillibactin in the supernatant of the SQR9 ( Xu et al., 2013Xu et al., , 2014). Genomic anal- ysis of SQR9 identified their gene clusters (bmyDABC, fenE-A, srfAA-AD, and dhbE-A) responsible for the synthesis of bacil- lomycin D, fengycin, surfactin and bacillibactin, respectively (Figure 2, Table S2). ...
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... Moreover, it was found that P. syringae BAF.1 siderophore demonstrated obvious antagonistic activity against F. oxysporum [34]. Interestingly, the bacillibactin siderophore produced by SQR9 was upregulated when it was confronted with fungi [35]. The siderophores of P. fluorescens BBc6R8 inhibited the growth of the actinomycete Streptomyces ambofaciens ATCC23877 [11]. ...
An endophytic symbiont P. aeruginosa-producing anticandidal siderophore was recovered from mangrove leaves for the first time. Production was optimal in a succinate medium supplemented with 0.4% citric acid and 15 µM iron at pH 7 and 35 °C after 60 h of fermentation. UV spectra of the acidic preparation after purification with Amberlite XAD-4 resin gave a peak at 400 nm, while the neutralized form gave a peak at 360 nm. A prominent peak with RP-HPLC was obtained at RT 18.95 min, confirming its homogeneity. It was pH stable at 5.0–9.5 and thermally stable at elevated temperatures, which encourages the possibility of its application in extreme environments. The minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) against Candida spp. Were in the range of 128 µg/mL and lower. It enhanced the intracellular iron accumulation with 3.2–4.2-fold (as judged by atomic absorption spectrometry) with a subsequent increase in the intracellular antioxidative enzymes SOD and CAT. Furthermore, the malondialdehyde (MDA) concentration due to cellular lipid peroxidation increased to 3.8-fold and 7.3-fold in C. albicans and C. tropicalis, respectively. The scanning electron microscope (SEM) confirmed cellular damage in the form of roughness, malformation, and production of defensive exopolysaccharides and/or proteins after exposure to siderophore. In conclusion, this anticandidal siderophore may be a promising biocontrol, nonpolluting agent against waterborne pathogens and pathogens of the skin. It indirectly kills Candida spp. by ferroptosis and mediation of hyperaccumulation of iron rather than directly attacking the cell targets, which triggers the activation of antioxidative enzymes.
... Moreover, it was found that P. syringae BAF.1 siderophore demonstrated obvious antagonistic activity against F. oxysporum [34]. Interestingly, the bacillibactin siderophore produced by SQR9 was upregulated when it was confronted with fungi [35]. The siderophores of P. fluorescens BBc6R8 inhibited the growth of the actinomycete Streptomyces ambofaciens ATCC23877 [11]. ...
... Similar results were obtained by Alvarez et al. [4] showing that the peptide synthetase genes for bacillomycin in B. amyloliquefaciens ARP 2 3, and fengycin and surfactin in B. amyloliquefaciens MEP 2 18, were detectable using PCR, but these lipopeptides were not detected in the culture supernatants from these strains. According to the literature, mutation of an essential gene, in appropriate culture conditions, the aggregation state of the culture medium where the bacterial cells developed or interaction between the bacterial antagonist and fungal pathogen have been reported as influencing factors for lipopeptide production [27][28][29][30][31][32]. Iturin is known for its strong antifungal property and hemolytic activity [4,11]. ...
This study explores beneficial bacteria isolated from the roots and rhizosphere soil of Khao Rai Leum Pua Phetchabun rice plants. A total of 315 bacterial isolates (KK1 to KK315) were obtained. Plant growth-promoting traits (phosphate solubilization and indole-3-acetic acid (IAA) production), and antimicrobial activity against three rice pathogens (Curvularia lunata NUF001, Bipolaris oryzae 2464, and Xanthomonas oryzae pv. oryzae) were assessed. KK074 was the most prolific in IAA production, generating 362.6±28.0 µg/ml, and KK007 excelled in tricalcium phosphate solubilization, achieving 714.2±12.1 µg/ml. In antimicrobial assays using the dual culture method, KK024 and KK281 exhibited strong inhibitory activity against C. lunata, and KK269 was particularly effective against B. oryzae. In the evaluation of antimicrobial metabolite production, KK281 and KK288 exhibited strong antifungal activities in cell-free supernatants. Given the superior performance of KK281, taxonomically identified as Bacillus sp. KK281, it was investigated further. Lipopeptide extracts from KK281 had significant antimicrobial activity against C. lunata and a minimum inhibitory concentration (MIC) of 3.1 mg/ml against X. oryzae pv. oryzae. LC-ESI-MS/MS analysis revealed the presence of surfactin A in the lipopeptide extract. The crude extract was non-cytotoxic to the L-929 cell line at tested concentrations. In conclusion, the in vitro plant growth-promoting and disease-controlling attributes of Bacillus sp. KK281 make it a strong candidate for field evaluation to boost plant growth and manage disease in upland rice.
... Increased chitinase activity in the diseased rhizosphere of the plants cultivated in the transformed soil compared to the soil from conventional field contributed to disease-suppressiveness against fungal phytopathogens (Sadeghi et al. 2017). Similarly, the increase in the abundance of genes contributing to disease-suppressiveness (prnD, fenA, and dhbA) in transformed soil than in the soil from conventional field observed in this study, indicated greater abundance of the bacterial phyla in organic field soil that conferred disease-suppressive effect (Li et al. 2014;Asmani et al. 2020;Jayaraman et al. 2021). However, Armalytė et al. (2019) reported no significant change in the dominant taxa in soil from organic and conventional fields, except for changes in the abundance of lower taxa. ...
... The native polypeptide chain is composed of the monomeric amino acids encoded by each gene of the operon (Lu et al. 2022). Based on transcriptional analysis of fengycin operon, fenA has been observed to be upregulated in the presence of fungal phytopathogens such as Verticillium dahliae, Fusarium solani, Rhizoctonia solani, Fusarium oxysporum, etc. (Li et al. 2014;Yang et al. 2022). Fengycin and bacillibactin have antifungal activities against a broad range of fungal phytopathogens. ...
... It is encoded by dhbA gene of the dhbABCDEF operon. The upregulation of dhbA has been reported in the presence of fungal phytopathogens likeVerticillium dahliae and Phytophthora parasitica (Li et al. 2014). ...
Organic agriculture is a sustainable method of farming, and confers disease-suppressing abilities to disease-conducive soils via specialized soil microbiomes. This study aimed at transforming a disease-conducive soil from a conventional field into disease-suppressive soil by inoculating soil from an organic field previously established as “disease-suppressive”. The effectiveness of the transformed soil was established with the model plant wheat (Triticum aestivum) grown under natural conditions, with regard to its potential in inhibiting fungal phytopathogens, Rhizoctonia solani and Fusarium oxysporum. The conducive soil inoculated with the disease-suppressive soil performed better than the control conducive soil in terms of reduced disease severity in plants, improved soil nutrient content, increased activity of hydrolytic enzymes, and increased abundance of structural and functional microbial markers. The study demonstrates the efficacy of the soil microbiome under long-term organic agriculture in transforming disease-conducive soil into disease-suppressive soils. Such practises are simple and easy to implement, and could greatly improve the sustainability and crop yield in developing countries.
... У Південній і Центральній Америці найбільшим їх виробником є Бразилія [133,134]. Крім представників роду Trichoderma, значну антагоністичну активність щодо фітопатогенів проявляють й інші ґрунтові мікроміцети, що належать до різних таксонів: Chaetomium [135,136], Gliocladium [137], Penicillium [138] та ін., а також бактерії, наприклад, представники родів Bacillus [139][140][141]. ...
... Supporting evidence can be found in previous studies where B. amyloliquefaciens SQR9 modified antifungal substance production against six different soil-borne fungal pathogens [35]. B. amyloliquefaciens PGPBacCA1 was identified to have surfactin and iturin in the liquid culture, whereas for the solid medium, an additional class of lipopeptide called fengycin was identified within the bacterial-fungal growth inhibition zone of strain PGPBacCA1 [36]. ...
Citrus canker caused by Xanthomonas citri subsp. citri is a devastating bacterial disease with severe implications for the citrus industry. Microorganisms possessing biocontrol capabilities against X. citri subsp. citri offer a highly promising strategy for healthy citrus management. In the present study, a broad-spectrum antagonist strain ZJLMBA1908 with potent antibacterial activity against X. citri subsp. citri was isolated from symptomatic lemon leaves, and identified as Bacillus amyloliquefaciens. Cell-free supernatant (CFS) of strain ZJLMBA1908 also exhibited remarkable antimicrobial activity, especially suppressing the growth of X. citri subsp. citri and Nigrospora oryzae, with inhibition rates of 27.71% and 63.75%, respectively. The antibacterial crude extract (CE) derived from the CFS displayed effective activity against X. citri subsp. citri. A preventive treatment using the CE significantly reduced the severity and incidence of citrus canker in a highly susceptible citrus host. Additionally, the CE maintained activity in the presence of protease and under a wide range of temperature and pH treatments. Applying high-performance liquid chromatography (HPLC) to separate and purify the CE resulted in the discovery of one highly potent anti-X. citri subsp. citri subfraction, namely CE3, which could completely inhibit the growth of X. citri subsp. citri. Liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI–MS) analysis revealed that CE3 mainly consisted of palmitic acid, surfactin C15, phytosphingosine and dihydrosphingosine. Taken together, the results contribute to the possible biocontrol mechanisms of B. amyloliquefaciens ZJLMBA1908, as well as providing a promising new candidate strain as a biological control agent for controlling citrus canker.
... To this end, in vitro co-culture either with direct physical contact (Ola et al., 2013;Zhang et al., 2014) or avoiding it (Li et al., 2014;Vallet et al., 2017), are viable strategies considering the complexity of BCA-PF interaction under natural conditions, where multiple factors are involved. Interaction responses may involve modification of growth patterns, selective production of antimicrobial metabolites, and transcriptome re-modeling. ...
... Under these conditions, bacterial colonies show less radial growth on the side adjacent to the fungus in comparison to the opposite side (Bartolini et al., 2019;Villa-Rodriguez et al., 2021). In another indirect co-culture, B. amyloliquefaciens SQR9, a lipopeptide/bacillibactin-producing strain, modified its antibiotics profile depending on the PF competitor (Li et al., 2014). ...
... These findings are consistent with several studies suggesting that CLPs produced by Bacillus spp. were affected when co-cultivated with various fungi [15,16,38] and provide further evidence of the regulation of CLPs produced by Bacillus spp. through direct interactions. ...
Fusarium wilt, caused by Fusarium oxysporum f. sp. cucumerinum (FOC), poses a serious threat to cucumber productivity. Compared to traditional chemical pesticides, biological control strategies have attracted more attention recently owing to their effectiveness against pathogens and their environmental safety. This study investigated the effect of white rot fungi Pleurotus ostreatus P5 on the production of cyclic lipopeptides (CLPs) of Bacillus amyloliquefaciens B2 and the potential co-culture filtrate of strains B2 and P5 to control cucumber Fusarium wilt. A PCR amplification of CLP genes revealed that B. amyloliquefaciens B2 had two antibiotic biosynthesis genes, namely, ituA and srf, which are involved in iturin A and surfactin synthesis. Liquid chromatography with tandem mass spectrometry (LC-MS/MS) revealed that CLPs derived from strain B2 contained two families, iturin A (C14, C15) and surfactin (C12–C17). The co-culture exhibited an enhanced accumulation of iturin A and surfactin compared to the monoculture of strain B2. Furthermore, the gene expressions of ituA and srf were both significantly upregulated when co-cultured with the fungus compared to monocultures. In an in vitro experiment, the co-culture filtrate and monoculture filtrate of B. amyloliquefaciens B2 inhibited mycelial growth by 48.2% and 33.2%, respectively. In a greenhouse experiment, the co-culture filtrate was superior to the monoculture filtrate in controlling cucumber Fusarium wilt disease and in the promotion of plant growth. Co-culture filtrate treatment significantly enhanced the microbial metabolic activity and decreased the abundance of FOC in the rhizosphere soil. These results show that the co-culture of P. ostreatus P5 and B. amyloliquefaciens B2 has great potential in cucumber Fusarium wilt disease prevention by enhancing the production of bacterial CLPs.
... Particularly, B. subtilis YM 10À20 is capable of producing antifungal substances (Abdelaziz et al., 2023). Additionally, Li et al. (2014) reported that the production of various antifungal compounds by the B. amyloliquefaciens strain SQR9 demonstrated activities against a broad spectrum of fungal soilborne pathogens, including F. solani, S. sclerotiorum, Verticillium dahliae Kleb, Phytophthora parasitica, and F. oxysporum. The effectiveness of Bacillus against root rot and damping brought on by R. solani has also been demonstrated by other researchers using a variety of antibiotics, including iturin A, surfactin, plipastatin, bacilysin, mycobacillin, and mycosubtilin (Hussain et al., 2022a,b). ...
For a variety of reasons, more and more individuals are searching for alternatives to synthetic chemicals. In addition to other factors, synthetic chemicals used in disease prevention and control have the potential to have harmful effects on the environment. As a remedy for plant illnesses that are spread through the soil, plant growth-promoting rhizobacteria (PGPR) are discussed in this chapter. Pesticide-resistant gram-positive bacteriophages and biocontrol agents, as well as biopesticides, biofertilizers, and soil inoculants, are among the various concepts and nomenclatures examined in this study. Biological control agents, biopesticides, and soil inoculants are all investigated in this study. As a biocontrol agent, PGPR has its advantages and disadvantages. We also discuss the possible hazards of utilizing PGPR. Metabolites of PGPR are examined in this study, as is their role in the control of soilborne illnesses. It accomplishes this by presenting many case studies that act as examples. For the use of growth-promoting rhizobacteria to combat soilborne diseases, there are several more interesting case studies included in this collection. The biocontrol activities of PGPR have been extensively documented. Among these are the creation of antibiotics, siderophores, and enzymes that dissolve cell walls, as well as the development of systemic resistance, the efficacy of root colonization, and rhizosphere competency.
... (3) fengycin family (synonymous to plipastatin) also with antifungal activity (e.g., Verticillium dahliae kleb, F. oxysporum, and Phytophthora parasitica; Li et al., 2014;Salazar et al., 2023). The general antimicrobial mechanism of lipopeptides is penetrating the cell membrane and forming aggregates with phospholipids, thereby changing the permeability of the cell membrane of target pathogens (Dimkic et al., 2022;Sevugapperumal et al., 2019). ...
Species of the genus Bacillus have been widely used for the biocontrol of plant diseases in the demand for sustainable agricultural development. New mechanisms underlying Bacillus biocontrol activity have been revealed with the development of microbiome and microbe‐plant interaction research. In this review, we first briefly introduce the typical Bacillus biocontrol mechanisms, such as the production of antimicrobial compounds, competition for niches/nutrients, and induction of systemic resistance. Then, we discussed in detail the new mechanisms of pathogen quorum sensing interference and reshaping of the soil microbiota. The “cry for help” mechanism was also introduced, in which plants can release specific signals under pathogen attack to recruit biocontrol Bacillus for root colonization against invasion. Finally, two emerging strategies for enhancing the biocontrol efficacy of Bacillus agents, including the construction of synthetic microbial consortia and the application of rhizosphere‐derived prebiotics, were proposed.
