Community Structures and Antifungal Activity of Root-Associated Endophytic Actinobacteria in Healthy and Diseased Cucumber Plants and Streptomyces sp. HAAG3-15 as a Promising Biocontrol Agent

Microorganisms related to plant roots are vital for plant growth and health and considered to be the second genome of the plant. When the plant is attacked by plant pathogens, the diversity and community structure of plant-associated microbes might be changed. The goal of this study is to characterize differences in root-associated endophytic actinobacterial community composition and antifungal activity between Fusarium wilt diseased and healthy cucumber and screen actinobacteria for potential biological control of Fusarium wilt of cucumber. In the present research, three healthy plants (also termed “islands”) and three obviously diseased plants (naturally infected by F. oxysporum f. sp. cucumerinum) nearby the islands collected from the cucumber continuous cropping greenhouse were chosen as samples. Results of culture-independent and culture-dependent analysis demonstrated that actinomycetes in the healthy roots were significantly more abundant than those of diseased roots. Moreover, there were seven strains with antifungal activity against F. oxysporum f. sp. cucumerinum in healthy cucumber roots, but only one strain in diseased cucumber roots. Out of these eight strains, the isolate HAAG3-15 was found to be best as it had the strongest antifungal activity against F. oxysporum f. sp. cucumerinum, and also exhibited broad-spectrum antifungal activity. Thus, strain HAAG3-15 was selected for studying its biocontrol efficacy under greenhouse conditions. The results suggested that the disease incidence and disease severity indices of cucumber Fusarium wilt greatly decreased (p < 0.05) while the height and shoot fresh weight of cucumber significantly increased (p < 0.05) after inoculating strain HAAG3-15. On the basis of morphological characteristics, physiological and biochemical properties and 100% 16S ribosomal RNA (rRNA) gene sequence similarity with Streptomyces sporoclivatus NBRC 100767T, the isolate was assigned to the genus Streptomyces. Moreover, azalomycin B was isolated and identified as the bioactive compound of strain HAAG3-15 based on analysis of spectra using a bioactivity-guided method. The stronger antifungal activity against F. oxysporum f. sp. cucumerinum, the obvious effect on disease prevention and growth promotion on cucumber seedlings in the greenhouse assay, and the excellent broad-spectrum antifungal activities suggest that strain HAAG3-15 could be developed as a potential biocontrol agent against F. oxysporum f. sp. cucumerinum used in organic agriculture. These results suggested that the healthy root nearby the infected plant is a good source for isolating biocontrol and plant growth-promoting endophytes.

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Pseudomonas protegens MP12: A plant growth-promoting endophytic bacterium with broad-spectrum antifungal activity against grapevine phytopathogens

Microbiological Research ◽

10.1016/j.micres.2018.11.003 ◽

2019 ◽

Vol 219 ◽

pp. 123-131 ◽

Cited By ~ 20

Author(s):

Marco Andreolli ◽

Giacomo Zapparoli ◽

Elisa Angelini ◽

Gianluca Lucchetta ◽

Silvia Lampis ◽

...

Keyword(s):

Antifungal Activity ◽

Plant Growth ◽

Broad Spectrum ◽

Endophytic Bacterium ◽

Plant Growth Promoting ◽

Growth Promoting

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Taxonomic Characterization, and Secondary Metabolite Analysis of Streptomyces triticiradicis sp. nov.: A Novel Actinomycete with Antifungal Activity

Microorganisms ◽

10.3390/microorganisms8010077 ◽

2020 ◽

Vol 8 (1) ◽

pp. 77 ◽

Cited By ~ 4

Author(s):

Zhiyin Yu ◽

Chuanyu Han ◽

Bing Yu ◽

Junwei Zhao ◽

Yijun Yan ◽

...

Keyword(s):

Antifungal Activity ◽

16S Rrna ◽

Sequence Similarity ◽

Triticum Aestivum L ◽

Biosynthetic Gene Cluster ◽

Rrna Gene ◽

Phenotypic Properties ◽

Genus Streptomyces ◽

Antagonistic Microorganisms ◽

Taxonomic Characterization

The rhizosphere, an important battleground between beneficial microbes and pathogens, is usually considered to be a good source for isolation of antagonistic microorganisms. In this study, a novel actinobacteria with broad-spectrum antifungal activity, designated strain NEAU-H2T, was isolated from the rhizosphere soil of wheat (Triticum aestivum L.). 16S rRNA gene sequence similarity studies showed that strain NEAU-H2T belonged to the genus Streptomyces, with high sequence similarities to Streptomyces rhizosphaerihabitans NBRC 109807T (98.8%), Streptomyces populi A249T (98.6%), and Streptomyces siamensis NBRC 108799T (98.6%). Phylogenetic analysis based on 16S rRNA, atpD, gyrB, recA, rpoB, and trpB gene sequences showed that the strain formed a stable clade with S. populi A249T. Morphological and chemotaxonomic characteristics of the strain coincided with members of the genus Streptomyces. A combination of DNA–DNA hybridization results and phenotypic properties indicated that the strain could be distinguished from the abovementioned strains. Thus, strain NEAU-H2T belongs to a novel species in the genus Streptomyces, for which the name Streptomyces triticiradicis sp. nov. is proposed. In addition, the metabolites isolated from cultures of strain NEAU-H2T were characterized by nuclear magnetic resonance (NMR) and mass spectrometry (MS) analyses. One new compound and three known congeners were isolated. Further, genome analysis revealed that the strain harbored diverse biosynthetic potential, and one cluster showing 63% similarity to natamycin biosynthetic gene cluster may contribute to the antifungal activity. The type strain is NEAU-H2T (= CCTCC AA 2018031T = DSM 109825T).

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Genome-wide screening antifungal genes in Streptomyces griseus S4-7, a Fusarium wilt disease suppressive microbial agent

FEMS Microbiology Letters ◽

10.1093/femsle/fnz133 ◽

2019 ◽

Vol 366 (12) ◽

Cited By ~ 1

Author(s):

Sung Won Hong ◽

Da-Ran Kim ◽

Youn Sang Kwon ◽

Youn-Sig Kwak

Keyword(s):

Antifungal Activity ◽

Secondary Metabolites ◽

Fusarium Wilt ◽

Streptomyces Griseus ◽

Wilt Disease ◽

Inverse Pcr ◽

Genus Streptomyces ◽

Fusarium Wilt Disease ◽

Genome Wide ◽

A Genome

ABSTRACT Streptomyces is a widely studied bacterial genus, particularly with regard to secondary metabolites and antibiotics production. Streptomyces griseus S4–7 was isolated from a strawberry Fusarium wilt disease suppressive soil, and its biological control ability has been well established. However, the antifungal mechanism of strain S4–7 is not yet fully understood at the molecular and biochemical level. Therefore, in this study we created a random mutant library for strain S4–7 with the Tn5 transposon element to investigate antifungal traits on a genome-wide scale. In total 4646 individual mutant strains were created and 13 mutants were selected based on loss of antifungal activity. The knockout genes were identified as electron transfer oxidoreductase (eto),sigma factor-70(sig70) and nrps by Inverse PCR (I-PCR). eto regulates the geranylgeranyl reductase gene, which is involved in terpenoid-quinone biosynthesis, an important factor in cell fitness. In the △eto strain, expression of wbl, a master regulator of the production of secondary metabolites, was significantly reduced. sig70 is responsible for the cell differentiation sensing mechanism in genus Streptomyces. △nrps showed decreased production of hybrid peptide-polyketide siderophores. These results suggest that S. griseus S4–7 may have various antifungal mechanisms, and each mechanism is essential to maximal antifungal activity.

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Characterization of Streptomyces spp. from Rice Fields as a Potential Biocontrol Agent against Burkholderia glumae and Rice Plant Growth Promoter

Agronomy ◽

10.3390/agronomy11091850 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1850

Author(s):

Mohamad Syazwan Ngalimat ◽

Erneeza Mohd Hata ◽

Dzarifah Zulperi ◽

Siti Izera Ismail ◽

Mohd Razi Ismail ◽

...

Keyword(s):

Plant Growth ◽

Plant Growth Promotion ◽

Biocontrol Agent ◽

Growth Promotion ◽

Antagonistic Activity ◽

Rice Fields ◽

Burkholderia Glumae ◽

Pgp Traits ◽

Genus Streptomyces ◽

Streptomyces Sp

The usage of plant growth-promoting (PGP) Streptomyces to improve plant growth is an alternative to existing strategies of chemical fertilizers that commonly caused environmental pollution. The aim of this study was to isolate and characterize PGP Streptomyces from Malaysian rice fields with antagonistic activity against Bacterial Panicle Blight disease in rice caused by Burkholderia glumae. A total of 50 bacterial isolates were recovered from the soil, rhizosphere, and endosphere; 22% showed antagonistic activity against B. glumae. Molecular identification using 16S rRNA amplification and phylogenetic tree analyses revealed that the antagonistic isolates belonged to the genus Streptomyces. Among the antagonistic isolates, Streptomyces sp. TBS5 (26.35 ± 0.14 mm) demonstrated the most antagonistic activity (p < 0.05) against B. glumae. Through API® ZYM analysis, the antagonistic isolates were revealed to have phosphoric hydrolase, ester hydrolase, peptide hydrolase, and glycosidase activities that play a crucial role in plant growth promotion. The antagonistic isolates demonstrated the highest (80%) PGP traits including able to fix nitrogen and solubilize phosphate, as well as produce siderophore and indole-3-acetic acid. Plant growth promotion assay under laboratory and greenhouse conditions were analyzed with the treatment of rice, Oryza sativa, seeds with the antagonistic isolates. Seeds treated with Streptomyces sp. TBS5, JAS2, R2-7, and TKR8 showed improvement in vigor index by more than 100% compared to water-treated control plants under both conditions. Augmentation of root length showed an overall increment of more than 101.5% under laboratory condition and 151.9% under greenhouse condition using Streptomyces sp. TBS5, JAS2, R2-7, and TKR8 treatments. Results suggest that Streptomyces sp. TBS5, JAS2, R2-7, and TKR8 are a good candidate to be developed as both biocontrol agent against B. glumae and PGP agent in rice.

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Characterization of Mesorhizobium strains for salt tolerance and wilt control: Their potential for plant growth promotion of chickpea (Cicer arietinum L.)

Legume Research - An International Journal ◽

10.18805/lr-3973 ◽

2018 ◽

Cited By ~ 1

Author(s):

Anju Sehrawat ◽

Aakanksha Khandelwal ◽

Satyavir Singh Sindhu

Keyword(s):

Salt Tolerance ◽

Plant Growth ◽

Fusarium Wilt ◽

Biocontrol Agent ◽

Growth Promotion ◽

Dry Weight ◽

Antagonistic Effect ◽

Maximum Increase ◽

Shoot Dry Weight ◽

Plant Growth Promoting

Mesorhizobium sp. indirectly promote the growth of plants as a biocontrol agent by inhibiting the growth of pathogens particularly Fusarium wilt of chickpea. Out of 24 Mesorhizobium isolates obtained from chickpea nodules, eight isolates showed antagonistic effect against Fusarium oxysporum. Salinity stress severely affects growth, nodulation and yield of chickpea. Mesorhizobium isolates were tested for their salt tolerance capacity at 1, 2, 4, 6 and 8% NaCl concentrations. Only two Mesorhizobium isolates MCA5 and MCA22 were found salt-tolerant upto 8% of salt concentration. Maximum increase (45.5%) in shoot dry weight was observed by inoculation of isolate MCA20 at 40 days of chickpea growth under chillum jar conditions, whereas isolate MCA23 resulted in 166.2% increase in root dry weight. Likewise, 112.6% increase in shoot dry weight was observed on inoculation of MCA14 isolate at 80th day of observation. Further extensive research is required to understand the mechanism of potential Mesorhizobium isolates of chickpea in controlling Fusarium wilt disease and salt tolerance. Selection of mesorhizobia with twin functional traits (plant growth promoting and biocontrol agent) can be exploited as future biofertilizer in chickpea.

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The potential of endophytic bacteria from the root of Eucalyptus pellita as a biocontrol agent against Ralstonia solanacearum

Biodiversitas Journal of Biological Diversity ◽

10.13057/biodiv/d220654 ◽

2021 ◽

Vol 22 (6) ◽

Author(s):

Yuliana Susanti ◽

GIYANTO GIYANTO ◽

MEITY SURADJI SINAGA ◽

KIKIN HAMZAH MUTAQIN ◽

BUDI TJAHJONO2

Keyword(s):

Plant Growth ◽

Ralstonia Solanacearum ◽

Endophytic Bacteria ◽

Biocontrol Agent ◽

Paenibacillus Polymyxa ◽

Rrna Gene ◽

Growth Promoter ◽

Growth Promoters ◽

Eucalyptus Pellita ◽

Protease Enzyme

Abstract. Susanti Y, Giyanto, Sinaga MS, Mutaqin KH, Tjahjono B. 2021. The potential of endophytic bacteria from the root of Eucalyptus pellita as a biocontrol agent against Ralstonia solanacearum. Biodiversitas 22: 3454-3462. Bacterial wilt disease (BWD) caused by Ralstonia solanacearum is one of the most damaging eucalyptus (Eucalyptus pellita F. Muell.) diseases. However, endophytic bacteria can be utilized to control it. This study aims to obtain and screen endophytic bacteria isolated from the root of eucalyptus as a biocontrol agent against BWD. A pathogenic R. solanacearum was isolated for artificial inoculation; subsequently, isolation, characterization and screening of the potential endophytic bacteria were conducted. Isolates of R. solanacearum demonstrated the pathogenicity for BWD in eucalyptus, with the highest virulence found in Rs 18. In total, 24 isolates of endophytic bacteria were obtained and screened for their biocontrol potential. The endophytic bacteria conveyed the capacity of antibiosis, indole acetic acid (IAA) hormone, nitrogen fixation, phosphate dissolution, protease enzyme and AHL-lactonase, which are the main indicators of bioagent characteristics in endophytic bacteria, as well as being plant growth stimulators. Four isolates were selected with the highest according to the analytic hierarchy process (AHP), identified on the 16S rRNA gene. Most isolates belonged to gram-negative bacteria. The four isolates, namely B33/77 (Serratia nematodiphila), B32/77 (Paenibacillus polymyxa), B13/497 (Brevundimonas olei) and B17/111 (Bacillus megaterium), indicated their potential for biocontrol as plant growth promoters. This study is the first report on the isolation of endophytic bacterial from eucalyptus roots with regard to its benefit as a plant growth promoter. It provides basic information about the characteristics of the endophytic bacteria, which showed potential as a biocontrol agent of R. solanacearum on eucalyptus.

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Potential Application of Rhizobacteria Isolated from the Central Highland of Vietnam as an Effective Biocontrol Agent of Robusta Coffee Nematodes and as a Bio-Fertilizer

Agronomy ◽

10.3390/agronomy11091887 ◽

2021 ◽

Vol 11 (9) ◽

pp. 1887

Author(s):

Dai Nam Nguyen ◽

San-Lang Wang ◽

Anh Dzung Nguyen ◽

Manh Dung Doan ◽

Dinh Minh Tran ◽

...

Keyword(s):

Plant Growth ◽

High Performance ◽

Biocontrol Agent ◽

Pathogenic Fungi ◽

Rrna Gene ◽

Inhibition Rate ◽

Egg Hatching ◽

Chromatography Analysis ◽

Robusta Coffee ◽

Central Highland

Robusta coffee is a major commercial crop in the Central Highland of Vietnam with high economic and export value. However, this crop is adversely affected by various pathogens, particularly nematodes. This study aimed to screen active anti-nematode rhizobacterial strains for sustainable coffee production. Among more than 200 isolates, the isolate TUN03 demonstrated efficient biocontrol with nearly 100% mortality of J2 coffee nematodes Meloidogyne spp. and 84% inhibition of nematode egg hatching. This active strain was identified as Pseudomonas aeruginosa TUN03 based on its 16S rRNA gene sequence and phylogenetic analysis. In greenhouse tests, the strain TUN03 significantly reduced the coffee nematode population in the rhizome-soil with an 83.23% inhibition rate and showed plant growth-promoting effects. Notably, this is the first report of the nematicidal effect of P. aeruginosa against coffee nematodes. This potent strain further showed an antifungal effect against various crop-pathogenic fungi and was found to be the most effective against Fusarium solani F04 (isolated from coffee roots) with a 70.51% inhibition rate. In addition, high-performance liquid chromatography analysis revealed that this bacterial strain also secretes plant growth regulators including indole acetic acid (IAA), gibberellic acid (GA3), kinetin, and zeatin in significant amounts of 100, 2700, 37, and 9.5 µg/mL, respectively. The data from this study suggest that P. aeruginosa TUN03 may be a potential biocontrol agent and biofertilizer for the sustainable production of Robusta coffee and other crops.

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Actinobacteria from Extreme Niches in Morocco and Their Plant Growth-Promoting Potentials

Diversity ◽

10.3390/d11080139 ◽

2019 ◽

Vol 11 (8) ◽

pp. 139 ◽

Cited By ~ 10

Author(s):

Ahmed Nafis ◽

Anas Raklami ◽

Noura Bechtaoui ◽

Fatima El Khalloufi ◽

Abdelkhalek El Alaoui ◽

...

Keyword(s):

Plant Growth ◽

Cannabis Sativa ◽

Extreme Environments ◽

Rrna Gene ◽

Genus Streptomyces ◽

Streptomyces Sp ◽

Streptomyces Spp ◽

Plant Growth Promoting Activities ◽

Plant Growth Promoting ◽

Growth Promoting

The objectives of this study were to assess actinobacterial diversity in five Moroccan extreme habitats and to evaluate their plant growth-promoting (PGP) activities. The soil samples were collected from different locations, including soils contaminated with heavy metals, from a high altitude site, from the desert, and from a marine environment. In total, 23 actinobacteria were isolated, 8 from Merzouga sand soil; 5 from Cannabis sativa rhizospheric soil; 5 from Toubkal mountain; 4 from a Draa sfar mining site; and 1 from marine soil. Based on their genotypic classification using 16S rRNA gene sequences, 19 of all belonged to the genus Streptomyces (82%) while the rest are the members of the genera Nocardioides (4.5%), Saccharomonospora (4.5%), Actinomadura (4.5%), and Prauserella (4.5%). Isolates Streptomyces sp. TNC-1 and Streptomyces sp. MNC-1 showed the highest level of phosphorus solubilization activity with 12.39 and 8.56 mg/mL, respectively. All 23 isolates were able to solubilize potassium, and 91% of them could grow under nitrogen-free conditions. The ability of the isolated actinobacteria to form indole-3-acetic acid (IAA) ranged from 6.70 to 75.54 μg/mL with Streptomyces sp. MNC-1 being the best IAA producer. In addition, all of the actinobacteria could produce siderophores, with Saccharomonospora sp. LNS-1 synthesizing the greatest amount (138.92 μg/mL). Principal coordinate analysis revealed that Streptomyces spp. MNC-1, MNT-1, MNB-2, and KNC-5; Saccharomonospora sp. LNS-1; and Nocardioides sp. KNC-3 each showed a variety of high-level plant growth-promoting activities. The extreme environments in Morocco are rich with bioactive actinobacteria that possess a variety of plant growth-promoting potentials that can further benefit green and sustainable agriculture.

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Streptomyces Application Triggers Reassembly and Optimization of the Rhizosphere Microbiome of Cucumber

Diversity ◽

10.3390/d13090413 ◽

2021 ◽

Vol 13 (9) ◽

pp. 413

Author(s):

Yanjiang Zhang ◽

Tian Zhang ◽

Zhijing Xue ◽

Yifan Liu ◽

Yongzhe Li ◽

...

Keyword(s):

Plant Growth ◽

Relative Abundance ◽

Stress Resistance ◽

Growth Promotion ◽

Alpha Diversity ◽

Fungal Communities ◽

Rrna Gene ◽

Cucumis Sativus L ◽

Genus Streptomyces ◽

Rhizosphere Microbiome

Streptomyces partum Act12 and Streptomyces roche D74 are biocontrol strains that can promote plant growth and enhance stress resistance in different crops. However, their effects on the rhizosphere microbiome and the role of the reassembled microbiome in plant growth promotion and stress resistance enhancement remain unclear. This study investigated the variation in the rhizosphere microbiome induced by Streptomyces application through a cucumber (Cucumis sativus L. cv. “Youliang”) pot experiment. The bacterial and fungal communities of rhizosphere soils inoculated with and without Streptomyces were, respectively, compared based on 16S rRNA and internal transcribed spacer rRNA gene sequences. Following Streptomyces application, the bacterial alpha diversity increased significantly, while the fungal alpha diversity exhibited the opposite trend. The bacterial and fungal communities’ compositions clearly shifted in the inoculated soil. Compared with the uninoculated control, the relative abundance of the genus Streptomyces increased by 68.3%, and the bacterial co-occurrence network in the rhizosphere soil was enriched significantly. The relative abundance of bacteria associated with nitrogen fixation was increased by 7.5% following Streptomyces application. Based on the results of this study, we conclude that the application of Streptomyces Act12 and D74 can be used to reassemble and optimize the rhizosphere microbiome of cucumber, which is conducive to plant survival.

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Diversity of Endophytic Actinomycetes Producing Indole-3- Acetic Acid and In vitro Evaluation of Plant Growth-promoting Activity on Brassica oleracea L.

Pertanika Journal of Tropical Agricultural Science ◽

10.47836/pjtas.44.2.02 ◽

2021 ◽

Vol 44 (2) ◽

Author(s):

Alimuddin Ali ◽

Nani Kurnia ◽

Andi Asrini Nurani Ulfah ◽

Putri Damayanti ◽

Herlina Rante ◽

...

Keyword(s):

Acetic Acid ◽

Plant Growth ◽

Rrna Gene ◽

Malt Extract ◽

Agar Block ◽

Genus Streptomyces ◽

Endophytic Actinomycetes ◽

Growth Promoting ◽

Indole 3 Acetic Acid

The evaluation of endophytic actinomycetes diversity, growth-promoting strain effects on cauliflower seeds germination, and in vitro organogenesis are the objectives in this study. Moreover, 15 strains from 125 isolates were determined to produce indole-3- acetic acid (IAA), where majority was obtained from roots (66.67%), followed by from branches (26.67%) and leaves (6.67%). Specifically, Jatropha sp. is a plant species with the most endophytic actinomycetes content compared to others. In addition, all endophytic Streptomyces strains were screened based on IAA production ability in vitro on yeast extract–malt extract broth (YMG) broth medium. The results showed the tendency for one strain with code Streptomyces sp. KMR-1E to generate a maximum IAA isolate from Cinnamomun sp. plant. Furthermore, the molecular taxonomy and phylogenetic analysis were recreated from 16S rRNA gene sequences, which attributed the KMR- 1E to genus Streptomyces. Meanwhile, plant growth promotion was evaluated under in vitro condition. This exposed the individual ability to enhance the shoot and root length of cauliflowers. The untreated cultures with a strain free agar block was used as control.

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