Ileana C. Farcasanu

Removing heavy metals from synthetic effluents using “kamikaze” Saccharomyces cerevisiae cells

One key step of the bioremediation processes designed to clean up heavy metal contaminated environments is growing resistant cells that accumulate the heavy metals to ensure better removal through a combination of biosorption and continuous metabolic uptake after physical adsorption. Saccharomyces cerevisiae cells can easily act as cation biosorbents, but isolation of mutants that are both hyperaccumulating and tolerant to heavy metals proved extremely difficult. Instead, mutants that are hypersensitive to heavy metals due to increased and continuous uptake from the environment were considered, aiming to use such mutants to reduce the heavy metal content of contaminated waters. In this study, the heavy metal hypersensitive yeast strain pmr1∆ was investigated for the ability to remove Mn2+, Cu2+, Co2+, or Cd2+ from synthetic effluents. Due to increased metal accumulation, the mutant strain was more efficient than the wild-type in removing Mn2+, Cu2+, or Co2+ from synthetic effluents containing 1–2xa0mM cations, with a selectivity

The antioxidant response induced by Lonicera caerulaea berry extracts in animals bearing experimental solid tumors.

{text{Mn}}^{{{text{2}} + }} > {text{Co}}^{{{text{2}} + }} ~ > {text{Cu}}^{{{text{2}} + }}

The Dual Action of Epigallocatechin Gallate (EGCG), the Main Constituent of Green Tea, against the Deleterious Effects of Visible Light and Singlet Oxygen-Generating Conditions as Seen in Yeast Cells

and also in removing Mn2+ and Cd2+ from synthetic effluents containing 20–50xa0μM cations, with a selectivity Mn2+ > Cd2+.

Overexpression of the PHO84 gene causes heavy metal accumulation and induces Ire1p-dependent unfolded protein response in Saccharomyces cerevisiae cells

The Ca2+‐dependent response to oxidative stress caused by H2O2 or tert‐butylhydroperoxide (tBOOH) was investigated in Saccharomycesu2003cerevisiae cells expressing transgenic cytosolic aequorin, a Ca2+‐dependent photoprotein. Both H2O2 and tBOOH induced an immediate and short‐duration cytosolic Ca2+ increase that depended on the concentration of the stressors. Sublethal doses of H2O2 induced Ca2+ entry into the cytosol from both extracellular and vacuolar sources, whereas lethal H2O2 shock mobilized predominantly the vacuolar Ca2+. Sublethal and lethal tBOOH shocks induced mainly the influx of external Ca2+, accompanied by a more modest vacuolar contribution. Ca2+ transport across the plasma membrane did not necessarily involve the activity of the Cch1p/Mid1p channel, whereas the release of vacuolar Ca2+ into the cytosol required the vacuolar channel Yvc1p. In mutants lacking the Ca2+ transporters, H2O2 or tBOOH sensitivity correlated with cytosolic Ca2+ overload. Thus, it appears that under H2O2‐induced or tBOOH‐induced oxidative stress, Ca2+ mediates the cytotoxic effect of the stressors and not the adaptation process.

Role of L-histidine in conferring tolerance to Ni2+ in Sacchromyces cerevisiae cells.

Lonicera caerulea is a species of bush native to the Kamchatka Peninsula (Russian Far East) whose berries have been extensively studied due to their potential high antioxidant activity. The aim of our work was to investigate the in vivo effects of the antioxidant action of Lonicera caerulea berry extracts on the dynamics of experimentally-induced tumors. Our data showed that aqueous Lonicera caerulaea extracts reduced the tumor volume when administered continuously during the tumor growth and development stages, but augmented the tumor growth when the administration of extracts started three weeks before tumor grafting. Prolonged administration of Lonicera caerulaea berry extracts induced the antioxidant defense mechanism in the tumor tissues, while surprisingly amplifying the peripheral oxidative stress.

Vaccinium corymbosum L. (blueberry) extracts exhibit protective action against cadmium toxicity in Saccharomyces cerevisiae cells.

The involvement of Ca2+ in the response to high Mn2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, and Hg2+ was investigated in Saccharomyces cerevisiae. The yeast cells responded through a sharp increase in cytosolic Ca2+ when exposed to Cd2+, and to a lesser extent to Cu2+, but not to Mn2+, Co2+, Ni2+, Zn2+, or Hg2+. The response to high Cd2+ depended mainly on external Ca2+ (transported through the Cch1p/Mid1p channel) but also on vacuolar Ca2+ (released into the cytosol through the Yvc1p channel). The adaptation to high Cd2+ was influenced by perturbations in Ca2+ homeostasis. Thus, the tolerance to Cd2+ often correlated with sharp Cd2+‐induced cytosolic Ca2+ pulses, while the Cd2+ sensitivity was accompanied by the incapacity to rapidly restore the low cytosolic Ca2+.

Interaction between lanthanide ions and Saccharomyces cerevisiae cells

Green tea extracts (GTEs) as well as their main component, the polyphenol epigallocatechin gallate (EGCG), are known for their versatile antioxidant, antimicrobial, antitumoral or anti-inflammatory effects. In spite of the huge beneficial action, there is increasing evidence that under certain conditions green tea and its components can be detrimental to living organisms. Using Saccharomyces cerevisiae strains with various defects in the response to oxidative stress, we found that GTEs or EGCG act in synergy with visible light, exhibiting either deleterious or protective effects depending on the solvent employed. Similar synergistic effects could be observed under singlet oxygen-generating conditions, such as light exposure in the presence of photosensitizers or UV-A irradiation, therefore solvent variance may represent a powerful tool to modulate the preparation of green tea extracts, depending on the intended target.

Calcium signaling and copper toxicity in Saccharomyces cerevisiae cells.

Pho84p, the protein responsible for the high-affinity uptake and transport of inorganic phosphate across the plasma membrane, is also involved in the low-affinity uptake of heavy metals in the Saccharomyces cerevisiae cells. In the present study, the effect of PHO84 overexpression upon the heavy metal accumulation by yeast cells was investigated. As PHO84 overexpression triggered the Ire1p-dependent unfolded protein response, abundant plasma membrane Pho84p could be achieved only in ire1Δ cells. Under environmental surplus, PHO84 overexpression augmented the metal accumulation by the wild type, accumulation that was exacerbated by the IRE1 deletion. The pmr1Δ cells, lacking the gene that encodes the P-type ATPase ion pump that transports Ca2+ and Mn2+ into the Golgi, hyperaccumulated Mn2+ even from normal medium when overexpressing PHO84, a phenotype which is rather restricted to metal-hyperaccumulating plants.