Steinberg (1938) proposed that gallium is required for growth in Aspergillus niger, but no essential biological function for gallium has been identified. Gallium and iron have similar ionic radii, and chelation by iron siderophores has been shown to be a mechanism of gallium uptake in fungi Muller et al, 1985). Gallium accumulation has also been observed in bacteria (Menon et al, 1978), and the toxicity of gallium is likely due to interference with iron-dependent metabolism (Al-Aoukaty, 1992; Olaka et al, 2000). Thiobacillus ferrooxidans can leach gallium from chalcopyrite, and evidence suggests that this organism can directly oxidize gallium sulfide (Torma, 1978). Gallium can be methylated by the vitamin B₁₂ derivative methylcobalamin in organic solvents, but gallium methylation under aqueous conditions has not been demonstrated (Beachley et al, 1987).

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Beachley OT, Kirss RU, Bianchini RJ, Royster TL. Chemistry of methylgallium(III) compounds in protic solvents. Organometallics 1987;6:724-7.

Steinberg RA. The essentiality of gallium to growth and reproduction of Aspergillus niger. J Agric Res. 1938;8:569-574.