Pepi M, Baldi F
Università di Siena, Dipartimento di Biologia Ambientale, Italy.
Biometals. 1992 Autumn;5(3):179-85. doi: 10.1007/BF01061326.
Two chromium(VI) resistant yeast strains (Candida sp. and Rhodosporidium sp.) were isolated from industrial wastes. Four different yeasts, three from the Industrial Yeast Collection and one of pharmaceutical origin, were also studied in relation to chromate toxicity and its alleviation by sulfur species. The growth of yeasts from industrial wastes was inhibited by 50% by high concentrations of Cr(VI): Candida sp. by 4 mM Cr(VI) and Rhodosporidium sp. by 10 mM Cr(VI) in Sabouraud Broth medium. The other Cr(VI)-sensitive yeasts were inhibited by 0.1 mM Cr(VI). The general mechanism of chromium resistance in Candida sp. and Rhodosporidium sp. was due to reduced uptake of chromium, but not to biological reduction from Cr(VI) to Cr(III). In Cr(VI)-sensitive yeasts, chromium was accumulated as much as 10-fold, as in Saccharomyces cerevisiae. Cr(VI) toxicity in Candida sp. was modulated from Cr(VI)-resistance to Cr(VI)-hypersensitivity depending on the addition of methionine, cysteine, sulfate and djenkolic acid. If Candida sp. was grown in the presence of S-amino acids, especially methionine, it was more resistant than if the sulfur source was sulfate. When sulfate transport was enhanced by addition of djenkolic acid, Candida sp. became hypersensitive. Rhosporidium sp. was always resistant to Cr(VI) because sulfate transport was inefficient and it assimilated sulfur as S-amino acids. Cr(VI)-sensitive yeasts required larger amounts of S-amino acids, especially methionine, to tolerate Cr(VI) toxicity. Cysteine was toxic for C.famata 6016 above 50 microM.
从工业废料中分离出两株抗六价铬酵母菌株（假丝酵母属和红冬孢酵母属）。还研究了另外四种不同的酵母，其中三种来自工业酵母菌种保藏中心，一种来自制药行业，考察了它们对铬酸盐毒性的反应以及硫物种对铬酸盐毒性的缓解作用。在萨布罗肉汤培养基中，高浓度的六价铬会抑制工业废料中酵母的生长，50% 的生长受到抑制：4 mM 六价铬可抑制假丝酵母属，10 mM 六价铬可抑制红冬孢酵母属。其他对六价铬敏感的酵母在 0.1 mM 六价铬时生长受到抑制。假丝酵母属和红冬孢酵母属抗铬的一般机制是铬的摄取减少，而非六价铬生物还原为三价铬。在对六价铬敏感的酵母中，铬的积累量高达酿酒酵母中的 10 倍。根据蛋氨酸、半胱氨酸、硫酸盐和豆科氨酸的添加情况，假丝酵母属中六价铬的毒性可从抗六价铬转变为超敏六价铬。如果假丝酵母属在含硫氨基酸尤其是蛋氨酸的环境中生长，其抗性比以硫酸盐为硫源时更强。添加豆科氨酸增强硫酸盐转运时，假丝酵母属会变得超敏。红冬孢酵母属始终对六价铬具有抗性，因为其硫酸盐转运效率低下，且将硫同化为含硫氨基酸。对六价铬敏感的酵母需要大量含硫氨基酸尤其是蛋氨酸来耐受六价铬毒性。半胱氨酸对 50 microM 以上的法塔假丝酵母 6016 有毒性。
