Ergosterol from Yeasts Promotes Helicobacter pylori Internalization into Candida albicans

Helicobacter pylori is a cholesterol-auxotrophic pathogen capable of internalizing into Candida albicans, where the yeast may serve as a protective intracellular niche under adverse environmental conditions. Because ergosterol is an analog of cholesterol, this study investigated its contribution to the interaction between H. pylori J99 and C. albicans ATCC 90028. Ergosterol was extracted from the wild-type strain ATCC 90028 and from Δerg4, Δerg5, and Δerg6 mutants, identified and quantified by UHPLC-MS/MS, and evaluated for its effects on bacterial viability, growth, chemotaxis, and intracellular internalization. Ergosterol showed no inhibitory effect on H. pylori viability within the tested concentration range. Ergosterol extracted from C. albicans ATCC 90028 enhanced bacterial growth and induced a rapid positive chemotactic response comparable to that elicited by cholesterol, whereas ergosterol-deficient mutants produced weaker responses. Internalization assays demonstrated that reduced ergosterol availability significantly decreased bacterial entry into yeast cells. These findings identify ergosterol as a key determinant of the H. pylori–C. albicans interaction, supporting the hypothesis that fungal sterols facilitate bacterial chemotaxis and intracellular persistence. This work provides new insights into the molecular basis of bacterial–fungal endosymbiosis and suggests that ergosterol-mediated interactions may contribute to the persistence and transmission of H. pylori.