A newly isolated Streptomyces rimosus strain capable of degrading deltamethrin as a pesticide in agricultural soil.

Chemical pesticides or insecticides with complex structures are highly abundant in the biosphere and have inevitable side effects on farmland, natural resources, and human health. Deltamethrin is the most popular and widely used pesticide that disrupts the cellular calcium channels. In the present study, isolated strains of bacteria were examined to determine the ones that were capable of degrading deltamethrin. Different species of bacteria were evaluated in terms of the capability to degrade deltamethrin. It is important to note that Streptomyces rimosus was able to degrade up to 200 mg/L deltamethrin concentration and could be grown in mineral salt medium agar containing deltamethrin to be used as a source of carbon and energy. The results demonstrated that there is a diversity of deltamethrin-degrading bacteria in agricultural soil ecosystems. The application of these bacteria, especially S. rimosus, might be used as a bioremediation technique to decrease pesticide contamination of the ecosystem.

Reclassification of Streptomyces rimosus subsp. paromomycinus as Streptomyces paromomycinus sp. nov.

Streptomyces rimosus is currently composed of two subspecies: Streptomyces rimosus subsp. rimosus and Streptomyces rimosus subsp. paromomycinus. The 16S rRNA gene similarity between type strains of these two subspecies is 99.03 %, whereas that between S. rimosus subsp. paromomycinus and Streptomyces chrestomyceticusis 100 %. To assess the taxonomic status of S. rimosus subsp. paromomycinus, genome sequencing was performed on the type strains of S. rimosus subsp. paromomycinus and S. chrestomyceticus. Digital DNA-DNA hybridization values between S. rimosus subsp. paromomycinus NBRC 15454T and S. rimosus subsp. rimosus ATCC 10970T and between S. rimosus subsp. paromomycinus NBRC 15454T and S. chrestomyceticus NBRC 13444T were 35.4 and 59.9 %, respectively, which are less than the thresholds for bacterial species delineation and indicate that S. rimosus subsp. paromomycinus is not S. rimosus, but an independent species different from S. rimosus and S. chrestomyceticus. In addition, phenotypic data also support that S. rimosus subsp. paromomycinus is distinct from S. chrestomyceticus. Therefore, S. rimosus subsp. paromomycinus should be reclassified as a novel species, for which we propose the name Streptomyces paromomycinus sp. nov. The type strain is NBRC 15454T (=ATCC 14827T=DSM 41429T=JCM 4541T=JCM 4871T=NRRL 2455T=VKM Ac-605T).

Isolation and identification of biocontrol agent Streptomyces rimosus M527 against Fusarium oxysporum f. sp. cucumerinum.

Actinomycetes have received considerable attention as biocontrol agents against fungal plant pathogens and as plant growth promoters. In this study, a total of 320 actinomycetes were isolated from various habitats in China. Among which, 77 strains have been identified as antagonistic activities against Fusarium oxysporum f. sp. cucumerinum which usually caused fusarium wilt of cucumber. Of these, isolate actinomycete M527 not only displayed broad-spectrum antifungal activity but also showed the strongest antagonistic activity against the spore germination of F. oxysporum f. sp. cucumerinum. In pot experiments, the results indicated that isolate M527 could promote the shoot growth and prevent the development of the disease on cucumber caused by F. oxysporum f. sp. cucumerinum. The control efficacy against seedling fusarium wilt of cucumber after M527 fermentation broth root-irrigation was up to 72.1% as compared to control. Based on 16S rDNA sequence analysis, the isolate M527 was identified as Streptomyces rimosus.

Efficient bioconversion of quercetin into a novel glycoside by Streptomyces rimosus subsp. rimosus ATCC 10970.

Incubation of quercetin with Streptomyces rimosus subsp. rimosus ATCC 10970 yielded an unusual glycosylated derivative. The structure of the product was determined to be quercetin-7-O-ß-4″-deoxy-hex-4″-enopyranosiduronic acid based on the spectral data. Quercetin was completely converted into the glycoside in 72 h.