Cadmium and calcium ions' effects on the growth of Pleurotus ostreatus mycelia are related to phosphatidylethanolamine content

Heavy metal Cd²⁺ can easily be accumulated by fungi, causing significant stress, with the fungal cell membrane being one of the primary targets. However, the understanding of the mechanisms behind this stress remains limited. This study investigated the changes in membrane lipid molecules of Pleurotus ostreatus mycelia under Cd²⁺ stress and the antagonistic effect of Ca²⁺ on this stress. Cd²⁺ in the growth media significantly inhibited mycelial growth, with increasing intensity at higher concentrations. The addition of Ca²⁺ mitigated this Cd²⁺-induced growth inhibition. Lipidomic analysis showed that Cd²⁺ reduced membrane lipid content and altered lipid composition, while Ca²⁺ counteracted these changes. The effects of both Cd²⁺ and Ca²⁺ on lipids are dose dependent and phosphatidylethanolamine appeared most affected. Cd²⁺ also caused a phosphatidylcholine/phosphatidylethanolamine ratio increase at high concentrations, but Ca²⁺ helped maintain normal levels. The acyl chain length and unsaturation of lipids remained unaffected, suggesting Cd²⁺ doesn't alter acyl chain structure of lipids. These findings suggest that Cd²⁺ may affect the growth of mycelia by inhibiting the synthesis of membrane lipids, particular the synthesis of phosphatidylethanolamine, providing novel insights into the mechanisms of Cd²⁺ stress in fungi and the role of Ca²⁺ in mitigating the stress.