Ilyas Sidra, Rehman Abdul
Department of Microbiology and Molecular Genetics, University of the Punjab, Quaid-e-Azam Campus, Lahore, 54590, Pakistan,
Environ Monit Assess. 2015 Jan;187(1):4115. doi: 10.1007/s10661-014-4115-9. Epub 2014 Nov 12.
In this study, we explored the multiple heavy metal-resistant yeast isolated from heavy metal-polluted environment. The isolated yeast showed maximum growth at 30 °C, pH 7.0, and the strain was identified as Candida tropicalis through 18S ribosomal RNA (rRNA) gene sequence analysis. Yeast cells grew well in medium containing different concentrations of heavy metal ions [CdCl₂, Pb(NO₃)₂, NaAsO₂, CuSO₄ and K₂Cr₂O₇]. Minimum inhibitory concentration (MIC) against different metal ions was ranged from 5 to 19 mM, and the metal resistance value against each metal observed by yeast cells was 5 mM (Cr), 10 mM (Cd), 15 mM (As), 14 mM (Cu) and 19 mM (Pb) and increased in the following order: Pb > Cu > As ≥ Cd > Cr. The total cellular glutathione, GSH/GSSG redox couple and metallothioneins like protein (MT) were assayed by growing cultures for 24 h and exposed to 100 mg/L of each heavy metal ion. Remarkable increase in γ-glutamylcysteinylglycine (GSH) level was determined in arsenic and cadmium treatment followed by chromium, lead and copper. Stressed cells had much more oxidized GSH than unstressed cells. GSH/GSSG ratio was significantly increased in cadmium and copper treatment in contrast to chromium, arsenic and lead. Statistical analysis revealed significantly higher cysteine level in all metal-treated samples as compared to control. Antioxidant glutathione transferase activity was not detected in metal-treated and untreated yeast samples. One-dimensional electrophoresis of proteins revealed marked differences in banding pattern of heavy metal-exposed yeast samples. A prominent 20 kDa band was observed in all treated samples suggesting that some differential proteins could be over-expressed during heavy metal treatment and might be involved in cell resistance mechanisms.
在本研究中，我们探索了从重金属污染环境中分离出的多种抗重金属酵母。分离出的酵母在30°C、pH 7.0条件下生长最佳，通过18S核糖体RNA（rRNA）基因序列分析将该菌株鉴定为热带假丝酵母。酵母细胞在含有不同浓度重金属离子[CdCl₂、Pb(NO₃)₂、NaAsO₂、CuSO₄和K₂Cr₂O₇]的培养基中生长良好。对不同金属离子的最低抑菌浓度（MIC）范围为5至19 mM，酵母细胞对每种金属的金属抗性值分别为5 mM（Cr）、10 mM（Cd）、15 mM（As）、14 mM（Cu）和19 mM（Pb），且抗性值按以下顺序增加：Pb＞Cu＞As≥Cd＞Cr。通过将培养物培养24小时并暴露于100 mg/L的每种重金属离子来测定细胞内总谷胱甘肽、GSH/GSSG氧化还原对和类金属硫蛋白（MT）。在砷和镉处理后，γ-谷氨酰半胱氨酰甘氨酸（GSH）水平显著增加，其次是铬、铅和铜。应激细胞比未应激细胞具有更多的氧化型GSH。与铬、砷和铅相比，镉和铜处理后GSH/GSSG比值显著增加。统计分析表明，与对照相比，所有金属处理样品中的半胱氨酸水平显著更高。在金属处理和未处理的酵母样品中均未检测到抗氧化谷胱甘肽转移酶活性。蛋白质的一维电泳显示，重金属暴露酵母样品的条带模式存在明显差异。在所有处理样品中均观察到一条突出的20 kDa条带，表明在重金属处理过程中可能有一些差异蛋白过度表达，并且可能参与细胞抗性机制。
