Studies On Secondary Metabolites And Nematicidal Activity Screening Of Bacteria And Actinomycetes

In this paper,80strains of bacteria and40strains of actinomycetes were assayed for their nematicidal activity and chemical richness using TLC method. As a result,51strains could kill more than50%nematode in24h. These isolates were identified on their16S rRNA sequences. Two strains YMF3.00141and P294had been selected to expand the fermentation and separate the secondary metabolites. The antimicrobial and nematicidal activities of compounds were evaluated in this paper. The main research results are described as follows:Based on their16S rRNA sequences, some strains were identified. They belonged to7genera including Arthrobacter, Escherichia, Acinetobacter, Alcaligenes, Wautersiella, Bacillus and Streptomyces. Among them, YMF3.00141was identified as Wautersiella falsenii, and P294was identified as Streptomyces sp..Five compounds were separated from strain YMF3.00141:cyclo-(L-Pro-L-Tyr)(1),4-phenylbutanoic acid(2),2(1H)-quinolinone (3),1H-indole-3-carboxaldehyde (4) and butyl-β-D-glucopyranoside (5), all of them were isolated for the first time from this strain. Nematicidal activity showed that compounds1,2,3and5had weak activity against the nematodes. Compound4had activity against Caenorhabditis elegans and Meloidogyne incognita. The entire C. elegans were dead in24h at400mg/L but M. incognita were dead in48h at the same concentration of compound4. After72h incubation in presence of200mg/L of compound4, it displayed94.00%and72.15%nematicidal activity against C. elegans and M. incognita, respectively. After72h incubation, the mortality of M. incognita was achieved46.18%even when the concentration of compound4was only50mg/L. Antibacterial activity showed that all of the compounds no obvious antibacterial activity.Five compounds were separated from strain P294:angumycinone C (6), angumycinone D (7) and X-14881E (8), Compound9and10are still identifed. Among them, compounds6and7are new compounds. Nematicidal activity showed that compounds6-8had no obvious activity. Compound6showed the strongest inhibitory activities against Bacillus subtilis Compound7has also showed a stronger inhibitory activity to B. subtilis and it had weak inhibitory activity against Pseudomonas aeruginosa. Antibacterial activity showed that compound8had inhibitory activity to all of target bacteria, and showed the strongest inhibitory against Escherichia coli and its inhibitory activity was weak to Staphylococcus aureus and B. subtilis.Highlight of this research:1. The chemical constituents of the fermentation extracts of Wautersiella falsenii were isolated and structurally identified for the first time. Furthermore, compound4(1H-indole-3-carboxaldehyde) had activity against Caenorhabditis elegans and Meloidogyne incognita.2. Two new compounds were isolated from Streptomyces sp. P294, and they showed different degree of inhibitory activity against the target bacteria (Escherichia coli, Bacillus cereus, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa).