A squalene–hopene cyclase in <i>Schizosaccharomyces japonicus</i> represents a eukaryotic adaptation to sterol-limited anaerobic environments
Jonna Bouwknegt, Sanne J. Wiersma, Raúl A. Ortiz‐Merino, Eline S. R. Doornenbal, Petrik Buitenhuis, Martin Giera, Christoph Müller, Jack T. Pronk
Abstract
Significance Biosynthesis of sterols requires oxygen. This study identifies a previously unknown evolutionary adaptation in a eukaryote, which enables anaerobic growth in absence of exogenous sterols. A squalene–hopene cyclase, proposed to have been acquired by horizontal gene transfer from an acetic acid bacterium, is implicated in a unique ability of the yeast Schizosaccharomyces japonicus to synthesize hopanoids and grow in anaerobic, sterol-free media. Expression of this cyclase in Saccharomyces cerevisiae confirmed that at least one of its hopanoid products acts as sterol surrogate. These observations provide leads for research into the structure and function of eukaryotic membranes and into the development of sterol-independent yeast cell factories for application in anaerobic processes.