Department of Soil Ecology, Helmholtz-Centre for Environmental Research GmbH - UFZ, Theodor-Lieser-Str. 4, 06120, Halle, Germany.
Department of Clinical Microbiology and Parasitology/ College of Medicine, King Khalid University, PO Box 641, Abha, 61314, Saudi Arabia.
BMC Microbiol. 2020 Feb 12;20(1):33. doi: 10.1186/s12866-020-1717-y.
Production of antibiotics to inhibit competitors affects soil microbial community composition and contributes to disease suppression. In this work, we characterized whether Streptomyces bacteria, prolific antibiotics producers, inhibit a soil borne human pathogenic microorganism, Streptomyces sudanensis. S. sudanensis represents the major causal agent of actinomycetoma - a largely under-studied and dreadful subcutaneous disease of humans in the tropics and subtropics. The objective of this study was to evaluate the in vitro S. sudanensis inhibitory potential of soil streptomycetes isolated from different sites in Sudan, including areas with frequent (mycetoma belt) and rare actinomycetoma cases of illness.
Using selective media, 173 Streptomyces isolates were recovered from 17 sites representing three ecoregions and different vegetation and ecological subdivisions in Sudan. In total, 115 strains of the 173 (66.5%) displayed antagonism against S. sudanensis with different levels of inhibition. Strains isolated from the South Saharan steppe and woodlands ecoregion (Northern Sudan) exhibited higher inhibitory potential than those strains isolated from the East Sudanian savanna ecoregion located in the south and southeastern Sudan, or the strains isolated from the Sahelian Acacia savanna ecoregion located in central and western Sudan. According to 16S rRNA gene sequence analysis, isolates were predominantly related to Streptomyces werraensis, S. enissocaesilis, S. griseostramineus and S. prasinosporus. Three clusters of isolates were related to strains that have previously been isolated from human and animal actinomycetoma cases: SD524 (Streptomyces sp. subclade 6), SD528 (Streptomyces griseostramineus) and SD552 (Streptomyces werraensis).
The in vitro inhibitory potential against S. sudanensis was proven for more than half of the soil streptomycetes isolates in this study and this potential may contribute to suppressing the abundance and virulence of S. sudanensis. The streptomycetes isolated from the mycetoma free South Saharan steppe ecoregion show the highest average inhibitory potential. Further analyses suggest that mainly soil properties and rainfall modulate the structure and function of Streptomyces species, including their antagonistic activity against S. sudanensis.
抗生素的生产抑制了竞争者，影响了土壤微生物群落的组成，并有助于疾病的抑制。在这项工作中，我们研究了产生大量抗生素的链霉菌是否能抑制土壤中一种与人类有关的病原菌，即苏丹链霉菌。苏丹链霉菌是导致放线菌病的主要病原体，放线菌病是热带和亚热带地区一种主要的、研究甚少的严重皮下疾病。本研究的目的是评估从苏丹不同地区（包括放线菌病高发区（放线菌病带）和罕见放线菌病病例区）分离的土壤链霉菌对苏丹链霉菌的体外抑制潜力。
使用选择性培养基，从代表苏丹三个生态区和不同植被及生态分区的 17 个地点共分离出 173 株链霉菌。在总共 173 株中，有 115 株（66.5%）对苏丹链霉菌表现出拮抗作用，其抑制程度不同。从南撒哈拉草原和林地生态区（苏丹北部）分离出的菌株比从位于苏丹南部和东南部的东苏丹稀树草原生态区或从中部和西部的萨赫勒地区相思林草原生态区分离出的菌株具有更高的抑制潜力。根据 16S rRNA 基因序列分析，分离株主要与沃雷链霉菌、恩尼斯考沙利链霉菌、灰色链霉菌和淡紫灰链霉菌有关。有三个分离株群与以前从人类和动物放线菌病病例中分离出的菌株有关：SD524（链霉菌亚群 6）、SD528（灰色链霉菌）和 SD552（沃雷链霉菌）。
本研究中超过一半的土壤链霉菌对苏丹链霉菌具有体外抑制潜力，这种潜力可能有助于抑制苏丹链霉菌的丰度和毒力。从无放线菌病的南撒哈拉草原生态区分离出的链霉菌表现出最高的平均抑制潜力。进一步的分析表明，主要是土壤特性和降雨量调节了链霉菌的结构和功能，包括其对苏丹链霉菌的拮抗活性。
