Abstract
Sterols and hopanoids are chemically and structurally related lipids mostly found in eukaryotic and bacterial cell membranes. Few bacterial species have been reported to produce sterols and this anomaly had originally been ascribed to lateral gene transfer (LGT) from eukaryotes. In addition, the functions of sterols in these bacteria are unknown and the functional overlap between sterols and hopanoids is still unclear. Gemmata obscuriglobus is a bacterium from the Planctomycetes phylum that synthesizes sterols, in contrast to its hopanoid-producing relatives. Here we show that sterols are essential for growth of G. obscuriglobus, and that sterol depletion leads to aberrant membrane structures and defects in budding cell division. This report of sterol essentiality in a prokaryotic species advances our understanding of sterol distribution and function, and provides a foundation to pursue fundamental questions in evolutionary cell biology.
Highlights
Sterols and hopanoids are chemically and structurally related lipids mostly found in eukaryotic and bacterial cell membranes
In order to broaden the studies of sterol function in bacteria, we experimentally investigated the contribution of sterol synthesis in Gemmata obscuriglobus, a member of the phylum Planctomycetes, unrelated to Proteobacteria
Terbinafine addition resulted in the development of phase-bright inclusions in approximately one-third of the cells within 4–5 h after the start of the time-lapse experiment (Fig. 3b–d), which roughly correspond to half a cell cycle in Discussion We report the essentiality of bacterial sterol synthesis genes, at least under laboratory growth conditions
Summary
Sterols and hopanoids are chemically and structurally related lipids mostly found in eukaryotic and bacterial cell membranes. Few bacterial species have been reported to produce sterols and this anomaly had originally been ascribed to lateral gene transfer (LGT) from eukaryotes. The function of bacterial sterols is currently unknown and the occurrence of sterol synthesis genes in bacteria has mostly been attributed to lateral gene transfer (LGT), either from eukaryotes to bacteria, or between bacteria[9,10,11]. In order to broaden the studies of sterol function in bacteria, we experimentally investigated the contribution of sterol synthesis in Gemmata obscuriglobus, a member of the phylum Planctomycetes, unrelated to Proteobacteria. G. obscuriglobus is ideally suited to study the functional differences between hopanoids and sterols We address these fundamental questions through a combination of genetic, chemical, and microscopy approaches
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