Bibi Fehmida, Strobel Gary A, Naseer Muhammad I, Yasir Muhammad, Khalaf Al-Ghamdi Ahmed A, Azhar Esam I
Special Infectious Agents Unit, King Fahd Medical Research Center, King Abdulaziz University, Jeddah, Saudi Arabia.
Department of plant sciences, Montana State University, Bozeman, MT, United States.
Front Microbiol. 2018 Jan 31;9:65. doi: 10.3389/fmicb.2018.00065. eCollection 2018.
Halophytes are associated with the intertidal forest ecosystem of Saudi Arabia and seemingly have an immense potential for yielding useful and important natural products. In this study we have aimed to isolate and characterize the endophytic and rhizospheric bacterial communities from the halophyte, , In addition these bacterial strains were identified and selected strains were further studied for bioactive secondary metabolites. At least 168 rhizspheric and endophytic bacteria were isolated and of these 22 were active antagonists against the oomycetous fungal plant pathogens, and . Active cultures were mainly identified with molecular techniques (16S r DNA) and this revealed 95.7-100% sequence similarities with relevant type strains. These microorgansims were grouped into four major classes: , β, and γ. Production of fungal cell wall lytic enzymes was detected mostly in members of and . PCR screening for type I polyketide synthases (PKS-I), type II polyketide synthases (PKS-II) and nonribosomal peptide synthetases (NRPS) revealed 13 of the 22 strains (59%) were positive for at least one of these important biosynthetic genes that are known to be involved in the synthesis of important antibiotics. Four bacterial strains of with potential antagonistic activity including two rhizobacteria, EA52 ( sp.), EA58 ( sp.) and endophytic bacteria . (EA65) and sp. (EA67) were selected for secondary metabolite analyses using LC-MS. As a result, the presence of different bioactive compounds in the culture extracts was detected some of which are already reported for their diverse biological activities including antibiotics such as Sulfamethoxypyridazine, Sulfamerazine, and Dimetridazole. In conclusion, this study provides an insight into antagonistic bacterial population especially the from , producing antifungal metabolites of medical significance and characterized taxonomically in future.
盐生植物与沙特阿拉伯的潮间带森林生态系统相关联，似乎在产生有用且重要的天然产物方面具有巨大潜力。在本研究中，我们旨在从盐生植物中分离并鉴定内生和根际细菌群落，此外，对这些细菌菌株进行了鉴定，并对选定的菌株进行了生物活性次生代谢产物的进一步研究。至少分离出了168株根际和内生细菌，其中22株对卵菌纲真菌植物病原体具有活性拮抗作用。活性培养物主要通过分子技术（16S rDNA）进行鉴定，结果显示与相关模式菌株的序列相似性为95.7%-100%。这些微生物被分为四大类：α、β和γ。真菌细胞壁裂解酶的产生主要在α和γ成员中检测到。对I型聚酮合酶（PKS-I）、II型聚酮合酶（PKS-II）和非核糖体肽合成酶（NRPS）的PCR筛选显示，22株菌株中有13株（59%）至少对这些已知参与重要抗生素合成的重要生物合成基因中的一个呈阳性。选择了四株具有潜在拮抗活性的细菌菌株，包括两株根际细菌EA52（芽孢杆菌属）、EA58（芽孢杆菌属）和两株内生细菌（EA65）和（EA67）进行LC-MS次生代谢产物分析。结果，在培养提取物中检测到了不同生物活性化合物的存在，其中一些已因其多种生物活性而被报道，包括抗生素如磺胺甲氧嗪、磺胺间二甲氧嘧啶和二甲硝唑。总之，本研究深入了解了拮抗细菌群体，特别是来自盐生植物的细菌群体，它们产生具有医学意义的抗真菌代谢产物，并将在未来进行分类学表征。
