Studies On Antimicrobial Activity Of Three Endophytes From Rosaceae Plants

Plant endophyte is one of the most important resources to discover new natural antibiotics. The investigation on the isolation and its antimicrobial activity of endophyptes from Rosaceae plants, including Rosa hybrida and Spiraea thunbergii was carried out. The results are as follows:1. Total 67 strains of endophytics were obtained in different separating medium, including 15 endophytic fungi and 52 actinomycetes. The results of antimicrobial tests indicated that 26 strains showed antibacterial activity and 6 strains showed antifungal activity. strains H21、GZ57 and GZ42 were selected for further research.2. Strain H21 was identified as Streptomyces finlayi. Its fermentation broth showed strong antibacterial and moderate antifungal activities against tested microorganisms. Holomycin, a member of the pyrrothine class of antibiotics, as well as N-acetyl-2-(4-hydroxyphenyl)-ethylamine and cyclo(L-Leu-L-Arg), was isolated from the broth of strain H21. Holomycin exhibited excellent antibacterial activity, and its MIC values against Ralstonia solanacearum, Pseudomonas syringaepv. Actinidiae, Bacillus cereus, Bacillus subtilis, Escherichia coli and Staphylococcus aureus were 0.156, 0.313, 0.078, 0.313, 0.156 and 0.313 μg/mL, respectively. Meanwhile, holomycin had strong antifungal activity against Botrytis cinerea, and it’s IC50 values against mycelial growth and spore germination were13.56 and 7.89 μg/mL, respectively.3. GZ57 is another actinomycete isolated from the Rosa hybrida Jacq.and named Streptomyces parvus GZ57. Tow compounds were btained from the fermentation broth and designated as GZ57-1 and GZ57-2. Based on MS and NMR data, they were identified as salicylamide andpyrrole-2-carboxamide, respectively. The results of Antibacterial tests showed that compound GZ57-2 exerted strong antibacterial activity against Ralstonia solanacearum, Pseudomonassyringae and Bacillus cereus, and the MIC values were 12.5, 6.25 and 12.5 μg/mL, respectively. Inhibition rate of compound GZ57-1 against Fusarium graminearumand Verticillium dahliawere42.4% and 40%, respectively.4. Strain GZ42 which was identified as Purpureocillium lilacinum was isolated from the Spiraea thunbergii.We three compounds Pseurotin A(GZ4201), ergosterol(GZ4202) and gergosterol gliotoxin derivatives(GZ4203) were isolated from its fermentation broth. Compounds GZ4202 showed no antibacterial activity to tested strains. The MICs of GZ4201 against Ralstonia solanacearum, Pseudomonas syringae, Bacillus subtilis, Bacillus cereus, Staphyloccocus aureusand and Escherichia coli were 50, 6.25, 25, 12.5, 12.5 and 12.5 μg/mL, respectively.