scholarly journals Epiphytic Bacteria from Sweet Pepper Antagonistic In Vitro to Ralstonia solanacearum BD 261, a Causative Agent of Bacterial Wilt

2021 ◽  
Vol 9 (9) ◽  
pp. 1947
Author(s):  
Tshifhiwa Paris Mamphogoro ◽  
Casper Nyaradzai Kamutando ◽  
Martin Makgose Maboko ◽  
Olayinka Ayobami Aiyegoro ◽  
Olubukola Oluranti Babalola

Biological control of plant pathogens, particularly using microbial antagonists, is posited as the most effective, environmentally-safe, and sustainable strategy to manage plant diseases. However, the roles of antagonists in controlling bacterial wilt, a disease caused by the most devastating and widely distributed pathogen of sweet peppers (i.e., R. solanacearum), are poorly understood. Here, amplicon sequencing and several microbial function assays were used to depict the identities and the potential antagonistic functions of bacteria isolated from 80 red and green sweet pepper fruit samples, grown under hydroponic and open soil conditions, with some plants, fungicide-treated while others were untreated. Amplicon sequencing revealed the following bacterial strains: Bacillus cereus strain HRT7.7, Enterobacter hormaechei strain SRU4.4, Paenibacillus polymyxa strain SRT9.1, and Serratia marcescens strain SGT5.3, as potential antagonists of R. solanacearum. Optimization studies with different carbon and nitrogen sources revealed that maximum inhibition of the pathogen was produced at 3% (w/v) starch and 2,5% (w/v) tryptone at pH 7 and 30 °C. The mode of action exhibited by the antagonistic isolates includes the production of lytic enzymes (i.e., cellulase and protease enzymes) and siderophores, as well as solubilization of phosphate. Overall, the results demonstrated that the maximum antimicrobial activity of bacterial antagonists could only be achieved under specific environmental conditions (e.g., available carbon and nitrogen sources, pH, and temperature levels), and that bacterial antagonists can also indirectly promote crop growth and development through nutrient cycling and siderophore production.

2020 ◽  
Vol 86 (21) ◽  
Author(s):  
Shengnan Zhou ◽  
Ge Liu ◽  
Rikuan Zheng ◽  
Chaomin Sun ◽  
Shimei Wu

ABSTRACT In the present study, a deep-sea bacterial strain designated Bacillus sp. strain wsm-1 was screened and found to exhibit strong antifungal activity against many plant-pathogenic fungi, and corresponding antifungal agents were thereby purified and determined by tandem mass spectrometry to be two cyclic lipopeptide homologs. These homologs, which were different from any previously reported lipopeptides, were identified to possess identical amino acid sequences of β-amino fatty acid-Asn-Ser-Asn-Pro-Tyr-Asn-Gln and deduced as two novel lipopeptides designated C14 iturin W and C15 iturin W. Electron microscopy observation indicated that both iturin W homologs caused obvious morphological changes and serious disruption of plasma membrane toward fungal cells, while C15 iturin W exhibited more serious cell damages than C14 iturin W did, which was well consistent with the results of the antifungal activity assays. To improve the yield and antifungal activity of iturin W, the effects of different carbon and nitrogen sources and amino acids on production of C14 iturin W and C15 iturin W were investigated. The results indicated that supplements of most of the detected carbon and nitrogen sources could increase the yield of C14 iturin W, but inhibit the yield of C15 iturin W, while supplements of tryptone and most of the detected amino acids could increase the yield of both C14 iturin W and C15 iturin W. IMPORTANCE Plant disease caused by pathogenic fungi is one of the most devastating diseases, which affects the food safety of the whole world to a great extent. Biological control of plant diseases by microbial natural products is more desirable than traditional chemical control. In this study, we discovered a novel lipopeptide, iturin W, with promising prospects in biological control of plant diseases. Moreover, the effects of different carbon and nitrogen sources and amino acids on production of C14 iturin W and C15 iturin W would provide a reasonable basis for the optimization of the fermentation process of lipopeptides. Notably, the structure of iturin W was different from that of any previously reported lipopeptide, suggesting that deep-sea microorganisms might produce many novel natural products and have significant potential in the development of biological products in the future.


2018 ◽  
Vol 69 ◽  
pp. 1-11 ◽  
Author(s):  
Willian Daniel Hahn Schneider ◽  
Roselei Claudete Fontana ◽  
Simone Mendonça ◽  
Félix Gonçalves de Siqueira ◽  
Aldo José Pinheiro Dillon ◽  
...  

2012 ◽  
Vol 496 ◽  
pp. 457-460
Author(s):  
Xiang Ping Kong

The growth conditions of a Geobacillus sp. were investigated by single-factor experiments. The strain was strictly aerobic bacterium, and could grow on hydrocarbons as the sole carbon source. The optimum carbon and nitrogen sources were 3.0% sucrose and 0.20% KNO3, respectively. The range of temperature, salinity and pH for the bacterial growth was 35-70 °C, 0-10% NaCl and 5.5-9.5, and good growth was obtained at 35-65 °C, 0.5-8% NaCl and 6.0-9.0, respectively. Particularly, the optimum temperature for the bacterial growth was between 50 °C and 60 °C. The strain had wide adaptability to the extreme conditions, and may be potentially applied to microbial enhanced oil recovery and oil-waste bioremediation technology.


2011 ◽  
Vol 10 (15) ◽  
pp. 2951-2958 ◽  
Author(s):  
Gutieacute rrez Rojas Ivonne ◽  
Beatriz Torres Geraldo Ana ◽  
Moreno Sarmiento Nubia

2011 ◽  
Vol 393-395 ◽  
pp. 851-854
Author(s):  
Lin Hua Zhang ◽  
Xin Zheng ◽  
Ya Jun Lang

In this study, the metabolic network of ectoine by Halomonas venusta DSM 4743 was established. The key nodes to influence the ectoine fermentation in metabolic flux and the basis during optimal control of fermentation process were investigated. The results showed that G6P, α-KG and OAA nodes were the key factors to influence the synthesis of ectoine. The metabolic flux distributions at the key nodes were significantly improved and ectoine concentration was enhanced in ectoine fermentation by adopting monosodium glutamate as the sole carbon and nitrogen sources, feeding monosodium glutamate and supplying oxygen limitedly. The batch fermentation was carried out in 10 L fermentor , the concentration and yield of ectoine was 8.4 g/L and 0.1 g/g, respectively, which were increased by 2.8 and 2 times, by comparison with batch fermentation using glucose as carbon source.


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