Oxidative stress, glutathione level and antioxidant response to heavy metals in multi-resistant pathogen, Candida tropicalis.
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.
Department of Microbiology and Molecular Genetics, University of the Punjab, Quaid-e-Azam Campus, Lahore, 54590, Pakistan, sidrailyas6@gmail.com.
Sidra
S
Ilyas
Abdul
A
Rehman
D000975:Antioxidants / Q000378:metabolism; D001151:Arsenic / Q000032:analysis; D002104:Cadmium / Q000032:analysis; D041022:Candida tropicalis / Q000302:isolation & purification; D002857:Chromium / Q000032:analysis; D003300:Copper / Q000032:analysis; D004784:Environmental Monitoring; D005978:Glutathione / Q000378:metabolism*; D008668:Metallothionein / Q000378:metabolism; D008670:Metals / Q000032:analysis; D019216:Metals, Heavy / Q000378:metabolism / Q000633:toxicity*; D018384:Oxidative Stress
D000975:Antioxidants; D008670:Metals; D019216:Metals, Heavy; D002104:Cadmium; D002857:Chromium; D003300:Copper; D008668:Metallothionein; D005978:Glutathione; D001151:Arsenic