Department of Biological Sciences, Birla Institute of Technology and Science BITS Pilani KK Birla Goa Campus, NH-17B, Goa, 403726, India.
BMC Microbiol. 2012 Jul 4;12:132. doi: 10.1186/1471-2180-12-132.
Because Candida albicans is resistant to several antifungal antibiotics, there is a need to identify other less toxic natural products, particularly antimicrobial proteins, peptides or bacteriocin like inhibitory substances. An attempt has been made to purify and characterise an anti-Candida compound produced by Enterococcus faecalis.
An anti-Candida protein (ACP) produced by E. faecalis active against 8 C. albicans strains was characterised and partially purified. The ACP showed a broad-spectrum activity against multidrug resistant C. albicans MTCC 183, MTCC 7315, MTCC 3958, NCIM 3557, NCIM 3471 and DI. It was completely inactivated by treatment with proteinase K and partially by pronase E.The ACP retained biological stability after heat-treatment at 90°C for 20 min, maintained activity over a pH range 6-10, and remained active after treatment with α-amylase, lipase, organic solvents, and detergents. The antimicrobial activity of the E. faecalis strain was found exclusively in the extracellular filtrate produced in the late logarithmic growth phase. The highest activity (1600 AU mL-1) against C. albicans MTCC 183 was recorded at 48 h of incubation, and activity decreased thereafter. The peptide showed very low haemagglutination and haemolytic activities against human red blood cells. The antimicrobial substance was purified by salt-fractionation and chromatography.Partially purified ACP had a molecular weight of approximately 43 KDa in Tricine-PAGE analysis. The 12 amino acid N terminal sequence was obtained by Edman degradation. The peptide was de novo sequenced by ESI-MS, and the deduced combined sequence when compared to other bacteriocins and antimicrobial peptide had no significant sequence similarity.
The inhibitory activity of the test strain is due to the synthesis of an antimicrobial protein. To our knowledge, this is the first report on the isolation of a promising non-haemolytic anti-Candida protein from E. faecalis that might be used to treat candidiasis especially in immunocompromised patients.
由于白色念珠菌对几种抗真菌抗生素具有耐药性，因此需要鉴定其他毒性较小的天然产物，特别是抗菌蛋白、肽或细菌素样抑制物质。本研究尝试从粪肠球菌中纯化和鉴定一种抗白色念珠菌的化合物。
从粪肠球菌中分离到一种抗白色念珠菌的蛋白（ACP），对 8 株白色念珠菌具有活性，并对其进行了部分纯化。该 ACP 对多药耐药的白色念珠菌 MTCC 183、MTCC 7315、MTCC 3958、NCIM 3557、NCIM 3471 和 DI 表现出广谱活性。该 ACP 经蛋白酶 K 处理完全失活，经胰蛋白酶 E 部分失活。该 ACP 经 90°C 热处理 20 分钟后仍保持生物稳定性，在 pH 6-10 范围内保持活性，经α-淀粉酶、脂肪酶、有机溶剂和洗涤剂处理后仍保持活性。该粪肠球菌菌株的抗菌活性仅存在于对数生长期晚期产生的细胞外滤液中。在孵育 48 小时时对白色念珠菌 MTCC 183 的活性最高（1600 AU mL-1），此后活性降低。该肽对人红细胞的血凝和溶血活性非常低。抗菌物质经盐析和色谱法纯化。经 Tricine-PAGE 分析，部分纯化的 ACP 的分子量约为 43 kDa。通过 Edman 降解获得 12 个氨基酸的 N 末端序列。通过 ESI-MS 从头测序，与其他细菌素和抗菌肽相比，推导的组合序列没有明显的序列相似性。
测试菌株的抑制活性是由于合成了一种抗菌蛋白。据我们所知，这是首次从粪肠球菌中分离出一种有前途的非溶血性抗白色念珠菌蛋白，该蛋白可能用于治疗念珠菌病，特别是在免疫功能低下的患者中。
