Terric acid对白色假丝酵母生长、细胞形态和大分子合成影响的研究

Effect of Terric acid on the growth,cellular morphology and macromolecular synthesis of C.albicans

摘要:

从海洋霉菌Aspergillus flavis No.179中分离纯化胞外抗真菌代谢产物Terric acid。以液体稀释法研究Terricacid在不同浓度下对酵母类真菌白色假丝酵母(Candida albicans)生长、细胞形态的影响。结果表明,Terric acid在较低浓度下能抑制测试菌株C.albicans AS2,538的生长,高浓度的Terric acid则能杀死C.albicans AS2,538细胞,其最小抑菌浓度和最小杀菌浓度分别为6.25μg/mL和50μg/mL。在亚抑菌浓度下,该物质能抑制C.albicans AS2,538假菌丝的形成,并引起细胞形态发生改变。当浓度达到50μg/mL时,细胞形态变得极不规则,有些细胞体积增大或破裂溶解。用¹⁴C-缬氨酸¹⁴C-胸腺嘧啶³H-尿嘧啶同位素标记物掺入的方法分别研究Terric acid对测试菌株C.albicans AS2,538蛋白质、DNA和RNA合成的影响,与对照相比,在含有5μg/mL Terric acid的培养基中培养4h后,¹⁴C-缬氨酸和1H-尿嘧啶的掺入量分别减少47.8%和70.7%,¹⁴C-胸腺嘧啶的掺入量没有明显的差异。此结果暗示Terric acid能抑制测试菌C.albicans S2,538蛋白质和RNA的合成，但对其DNA的合成没有明显影响。

Abstract:

Terric acid，an antifungal metabolites produced by a marine mold Aspergillus flavis No.179,was isolated and purified. The effects of terric acid at different concertrations on the growth and cellular morphology of C. albicans AS2,538 were studied by the method of liquid dilution. The substance inhibits the growth of C. albicans AS2,538 obviously at low concentration and has fungicidal action at high concentration. The minimum inhibiting concentrations(MIC) and minimum lethal concentrations(MLC) on C. albicans AS2,538 were 6.25μg/mL and 50μg/mL, respectively. At Sub-MIC（3.13μg/mL）, terric acid inhibited the formation of pseudo-hyphal of C. albicans AS2,538 and caused cell morphological change. After addition of terric acid to the medium to final concentration of 50μg/mL, cell morphology of C. albicans AS2,538 was irregular and some cells turned bigger and disrupted. The effects of terric acid on the synthesis of macromolecules, DNA, RNA or proteins of C. albicans AS2,538 were estimated by measurement of incorporation of radioactive precursors,¹⁴C-Thymidine, ³H-Uridine or¹⁴C-Valine, respectively. When C. albicans AS2,538 was incubated for 4h in 5 g/mL terric acid medium, the incorporation of radioactive isoleucine and uridine decreased 47.8%, 70.7%, respectively, Compared with controls incubated in commonly medium. However, the incorporation of ［3H］thymidine did not have significant change. This results indicated that terric acid inhibits the synthesis of protein and RNA but have no effect on DNA synthesis in a C．albicans AS2,538.