链霉菌HKIB0006中collismycin A葡萄糖酸修饰产物的发现

Discovery of products of collismycin A modified with gluconic acid in Streptomyces sp. HKIB0006

摘要:

【背景】2,2'-联吡啶类天然产物是一类由放线菌产生的抗菌化合物，抑制真菌活性显著，结构特征为包含2,2'-联吡啶片段。该类化合物未发现经后修饰的失活产物，其自抗性机制尚未明确。【目的】通过分离纯化并鉴定2,2'-联吡啶类化合物的后修饰产物，测试其抗真菌活性，评价后修饰对抗真菌活性的影响，初步探求2,2'-联吡啶类化合物存在的自我保护机制。【方法】利用纸片扩散法筛选对真菌有拮抗能力的放线菌并分离纯化该菌株；通过基因组测序及分析对其进行鉴定；利用硅胶柱色谱、高效液相色谱等手段分离纯化目标化合物，通过核磁共振波谱和质谱鉴定其结构；测定目标化合物抗真菌活性；最后通过序列比对来分析推测糖基转移酶。【结果】在链霉菌(Streptomyces sp.) HKIB0006中鉴定了2个2,2'-联吡啶类化合物。其中一个为新结构11-O-gluconicacid-collismycin A (1)，为已知抗生素collismycin A (2)的11位葡萄糖酸修饰产物，实验表明1的抗真菌活性消失。【结论】对化合物1和2进行抗菌活性测试，活性测试发现葡萄糖酸修饰导致1的抗菌活性丧失，推测葡萄糖酸修饰可能是2,2'-联吡啶类化合物的一种自抗性机制，该修饰可能是菌株HKIB0006在与2长期共存中进化出的自我保护策略之一。

关键词:链霉菌;2,2′-联吡啶类化合物;抗菌活性;糖基转移酶

Abstract:

[Background] 2,2'-bipyridines, a class of antimicrobial compounds produced by actinomycetes, have significant antifungal activities and are featured by the 2,2'-bipyridine moiety. No deactivated compound after post-translational modification of the known 2,2'-bipyridines has been discovered, and the self-resistance mechanisms of microorganisms to these compounds remain to be reported. [Objective] To isolate, identify, and determine the antifungal activities of 2,2'-bipyridines from Streptomyces sp. HKIB0006, evaluate the effect of post-translational modification on the antifungal activity, and decipher the self-resistance mechanism of the strain to 2,2'-bipyridines. [Methods] We screened out a Streptomyces strain with anti-fungal activity by the disk diffusion method and then identified the strain by genome sequencing. The target compounds were separated by silica gel column chromatography and HPLC, and their structures were elucidated by MS and nuclear magnetic resonance spectroscopy. The antifungal activities of the isolated compounds were evaluated, and a glycosyltransferase responsible for the self-resistance was revealed by sequence alignment. [Results] Two 2,2'-bipyridines were isolated from the fermentation broth of Streptomyces sp. HKIB0006. One was a new compound named as 11-O-gluconicacid-collismycin A (1), and the other was the known antibiotic collismycin A (2). The antifungal assay of 1 and 2 showed that 1 was inactive and 2 was active. [Conclusion] The antibacterial activity of compounds 1 and 2 was tested. The compound 1 is a gluconic acid modification product of collismycin A, and it is inactive due to the gluconic acid modification. According to genetic analysis, we propose that the gluconic acid modification may represents one of the self-resistance mechanisms of strain HKIB0006 against collismycin A.

Key words:Streptomyces sp.;2,2′-bipyridine;antimicrobial activity;glycosyltransferase