Heavy metals and thiol pool in three strains of Tetracladium marchalianum

Abstract

Growth of three strains of Tetracladium marchalianum was inhibited by Cd-, and, to a lesser extent, by Cu-and Zn-chloride. In the presence of 50 µM Cd(II), all strains increased total thiol and glutathione production to 6, 11, and 21 µmoles · mg -1 dry mass, respectively. Cd(II) also induced the synthesis of one to several compounds reacting with 5,5'-dithio-bis-(2-nitrobenzoic acid). In order to identify buffer-soluble thiolic compounds other than cysteine, γ-EC and γ-ECG (glutathione) were analyzed and confirmed by mass spectrometry. No water soluble sulfides were detectable in any of the culture filtrates, but Cd(II) exposure at a concentration of 50 µM raised sulfide levels in the mycelia of two of the strains between 3 and 7-fold, Cu(II) and Zn(II) had no effect. Energy Dispersive X-ray-analysis (EDX) and Electron Spectrometry-Images (ES-I) of one strain revealed increased levels of Cu and Zn in the cytoplasm and even higher levels in vacuolar precipitates. Zn and Cu are accumulated in the vacuoles as polyphosphates, identified by Electron Energy Loss-Spectrometry (EELS). Cd was found only in the vacuoles.

Stress response in two strains of the aquatic hyphomycete Heliscus lugdunensis after exposure to cadmium and copper ions

“…This is similar to the findings of Pawlik-Skowronska (2003) who found that the Zn 2+ tolerant alga Stigeoclonium tenue from a highly contaminated site produced more thiols than the same species from an unpolluted site. The differences between the two H. lugdunensis strains also confirm results from other aquatic hyphomycetes (Miersch et al 1997(Miersch et al , 2001(Miersch et al , 2005. Another H. lugdunensis strain, harvested during the stationary phase, increased its internal thiol pool by 4 lmol g )1 dry mass at Cd 2+ concentrations of up to 200 lM Cd 2+ (Miersch et al 1997), while exposure to copper had no effect.…”

“…Another H. lugdunensis strain, harvested during the stationary phase, increased its internal thiol pool by 4 lmol g )1 dry mass at Cd 2+ concentrations of up to 200 lM Cd 2+ (Miersch et al 1997), while exposure to copper had no effect. Varicosporium elodeae and Tetracladium marchalianum behaved in a similar manner (Miersch et al 1997(Miersch et al , 2005. In the zygomycete Mucor racemosus, cadmium caused an increase of the thiol pool with a simultaneous decrease of glutathione and induction of phytochelatins whereas copper had no effect (Miersch et al 2001).…”

“…Thiols are essential agents in cellular redox signalling and control in animals (Moran et al 2001), plants (Noctor et al 2002) and fungi (Po´csi et al 2004). Some aquatic hyphomycetes respond to Cd 2+ , but not to Cu 2+ or Zn 2+ , by increased synthesis of SH-containing compounds (Miersch et al 1997(Miersch et al , 2001(Miersch et al , 2005. The antioxidant defence system in several plants (Mittler et al 2004) and fungi (Amicarelli et al 1999;Avery, 2001;Po´csi et al 2004) has been shown to consist of several enzymes and low molecular weight antioxidants.…”

Targeting Genes of Cd Induced Oxidative Stress Response in Yeasts

“…Both yeast strains were viable even when 1.5 mmol/l cd(no 3 ) 2 was added to the growth medium. this could be attributed to the fact that in S. pombe and C. glabrata, similarly to plants, Cd detoxification involves synthesis of phytochelatins (27). Surprisingly, the growth of H. polymorpha and R. graminis was not significantly impaired even when very high cadmium concentrations were used ( Fig.…”

“…Another interesting observation was the higher resistance of H. polymorpha to Cd. Until recently, it was considered that the sequestration of this heavy metal in H. polymorpha occurs similarly to that found in Saccharomyces cerevisiae (with glutathione being the main cd intracellular chelator), but different from Schizosaccharomys pombe and Candida glabrata (27). however, several papers report identification of cadmium-ion tolerant Hansenula species (31,44), suggesting that much profounder investigations should be made on the cadmium tolerance of these yeast microorganisms.…”