Al-toxicity studies in yeast using gallium as an aluminum analogue

Abstract

Aluminum (Al) is normally present in soils as the insoluble, harmless Al2O3. The highly toxic Al3+ and AlOH2+ monomeric cations are formed in acid soils but there is little consensus on the physiological basis of Al toxicity in plants. A major factor that has retarded progress in understanding aluminum toxicity in vascular plants is the lack of a convenient radioisotope for Al. Yeast and vascular plants share similar membrane transport mechanisms and so yeast (Saccharomyces cerevisiae) provides a convenient model system for studies of Al-toxicity. Al and gallium (Ga) have closely similar toxic effects on the yeast cells (Ki approximately 100 mmol m-3) and Ga3+ and Al3+, respond similarly to pH and are both reversible by a chelation agent (citric acid). We tested the feasibility of using 67Ga radioisotope as a tracer for Al transport with the view of using it to investigate the mechanism of Al uptake and toxicity in plants. The clinically available 67Ga citrate is unsuitable to use as an aluminum analogue because the chelated form is not toxic. Arrangements need to be made for it to be supplied as 67GaCl3. Large amounts of 67Ga rapidly bind to the cell wall of yeasts with a t 1/2 of approximately 1 s. There is a very slow net uptake of 67Ga into a second phase, presumably the cytoplasm. Uptake into the slow phase has a Vmax of only approximately 16 +/- 4 pmol m(-2) s(-1) (n = 16). The Km of 67Ga uptake could not be precisely determined but is below 100 mmol m(-3) (45 +/- 42 mmol m(-3), n = 16).

The suitability of gallium as a substitute for aluminum in tracing experiments

“…There was also evidence that Ga did not affect the fertility of the snails to the same extent as Al. Similarly, Al is more toxic than Ga to the giant alga Chara coralline (Reid et al 1996), whilst Al and Ga exhibit similar levels of toxicity in yeast (Ritchie and Raghupathi 2008). There are few comparative data regarding the toxicity of Al and Ga in animals, but the observations from our study, as well as those above, indicate that the toxicity of Ga is at least no higher than that of Al and so would not differentially affect snail behaviour in any metal tracing experiment.…”

Identification of aluminium transport-related genes via genome-wide phenotypic screening of Saccharomyces cerevisiae

“…The growth conditions of yeast at acidic pH (B4.0) are ideal for Al 3+ ] precipitates out. 9,10 Secondly, the organismal nature and genetically-modified resources of S. cerevisiae have been greatly explored for investigating a broad array of biological problems, such as oxidative stress and aluminium toxicity, carried out in our laboratory. 4,11 In this study, we aimed to identify Al 3+ transport-related genes by a detailed screening of the Al 3+ tolerant phenotype from the complete collection of yeast deletion mutants.…”

Modeling and simulation of biomass anaerobic digestion for high biogas yield and CO2 mineralization

“…Particularly, during the hydrolysis stage, yeast can accelerate the reaction rates as hydrolysis often takes a longer time [45]. The spread of yeast is also possible because anaerobic digester media is usually enriched with nutrients from the hydrolysis and breakdown of degradable biomass [46]. The yeast aids in converting the degradable waste to neutral ethanol instead of propionic or butyric acid during the anaerobic digestion process [47][48][49][50][51].…”