Elfeky Nora, Elsalam Aya Abd, El-Sabbagh Sabha, Abd El-Motleb Asmaa
Botany and Microbiology Department, Faculty of Science, Menoufia University, Menoufia, Egypt.
Environmental Research Department, Theodor Bilharz Research Institute, Giza, Egypt.
AMB Express. 2025 Aug 22;15(1):125. doi: 10.1186/s13568-025-01927-0.
Actinomycetes, are abundant sources of bioactive secondary metabolites with potential antibacterial and molluscicidal effects. This work aims to isolate and characterize actinomycetes strains from Egyptian soil, emphasizing the evaluating their antibacterial efficiency, optimizating their metabolite production, and assessing molluscicidal activities against Biomphalaria alexandrina (B. alexandrina), an intermediate host of Schistosoma mansoni (S. mansoni). Nineteen actinomycetes isolates were screened for antimicrobial activity against Escherichia coli (E. coli), Salmonella typhi (S. typhi), Pseudomonas aeruginosa (P. aeruginosa), Staphylococcus aureus (S. aureus), Candida albicans (C. albicans), and Penicillium marneffei (P. marneffei). Isolate No. 10, later identified as Streptomyces rochei ASN (S. rochei ) via 16 S rDNA sequencing and phylogenetic analysis, exhibited broad-spectrum antimicrobial activity and was selected for further study. Production media optimization revealed that modified nutritional agar, starch as a carbon source, sodium nitrate as a nitrogen source, and 25 °C incubation maximized antimicrobial metabolite production. Antibacterial activity increased with extended incubation time, peaking at 8 days. Dose-dependent inhibition was observed when different concentrations (20-80%) of cell-free supernatant (CFS) from S. rochei ASN were applied to test pathogens, with S. aureus, C. albicans, and P. marneffei being most susceptible. Scanning electron microscopy revealed severe cellular and structural damage in treated microbes. The CFS also demonstrated significant molluscicidal activity, with LC₅₀ and LC₉₀ values of 26.85 ppm and 40.95 ppm, respectively. It inhibited the hatchability of B. alexandrina eggs in a concentration- and age-dependent manner, and exerted rapid, dose-dependent mortality against S. mansoni miracidia and cercariae. Histological examinations of exposed snails showed degeneration in both hermaphrodite and digestive glands, including disrupted acinar structures, damaged oocytes and spermatocytes, vacuolated digestive cells, and degenerated secretory cells. S. rochei ASN, isolated from Egyptian soil, exhibits potent antimicrobial and molluscicidal activities. Its bioactivity is significantly influenced by growth conditions and medium composition. The strain holds promise as a natural biocontrol agent against pathogenic microbes and snail vectors involved in schistosomiasis transmission, warranting further pharmacological and ecological investigations.
放线菌是具有潜在抗菌和杀螺作用的生物活性次生代谢产物的丰富来源。这项工作旨在从埃及土壤中分离和鉴定放线菌菌株，重点评估它们的抗菌效率，优化其代谢产物的产生，并评估对曼氏血吸虫中间宿主亚历山大双脐螺的杀螺活性。对19株放线菌分离株进行了针对大肠杆菌、伤寒沙门氏菌、铜绿假单胞菌、金黄色葡萄球菌、白色念珠菌和马尔尼菲青霉的抗菌活性筛选。分离株10号，后来通过16S rDNA测序和系统发育分析鉴定为罗氏链霉菌ASN，表现出广谱抗菌活性，并被选作进一步研究。生产培养基优化表明，改良营养琼脂、淀粉作为碳源、硝酸钠作为氮源以及25℃培养可使抗菌代谢产物产量最大化。抗菌活性随培养时间延长而增加，在8天时达到峰值。当将不同浓度（20-80%）的罗氏链霉菌ASN无细胞上清液应用于测试病原体时，观察到剂量依赖性抑制，金黄色葡萄球菌、白色念珠菌和马尔尼菲青霉最为敏感。扫描电子显微镜显示处理过的微生物细胞和结构严重受损。该无细胞上清液还表现出显著的杀螺活性，LC₅₀和LC₉₀值分别为26.85 ppm和40.95 ppm。它以浓度和年龄依赖性方式抑制亚历山大双脐螺卵的孵化率，并对曼氏血吸虫毛蚴和尾蚴产生快速、剂量依赖性的致死作用。对暴露蜗牛的组织学检查显示雌雄同体腺和消化腺均发生退化，包括腺泡结构破坏、卵母细胞和精母细胞受损、消化细胞空泡化以及分泌细胞退化现象。从埃及土壤中分离出的罗氏链霉菌ASN表现出强大的抗菌和杀螺活性。其生物活性受生长条件和培养基组成的显著影响。该菌株有望作为一种天然生物防治剂，对抗参与血吸虫病传播的致病微生物和蜗牛媒介，值得进一步进行药理学和生态学研究。
