Lipidome of the Bacteroides Genus Containing New Peptidolipid and Sphingolipid Families Revealed by Multiple-Stage Mass Spectrometry

Abstract

The anaerobic bacteria of the Bacteroides fragilis group including Bacteroides thetaiotaomicron, B. fragilis, Bacteroides vulgatus, and Bacteroides ovatus in genus Bacteroides are among the most commonly found human gut microbiota. They are generally commensal but are also opportunistic pathogens. Both the inner and outer membranes of the Bacteroides cell envelope contain abundant lipids with diversified structures, and dissection of the lipid composition of the inner and outer membrane fractions is important for understanding the biogenesis of this multilaminate wall structure. Here, we describe mass spectrometry-based approaches to delineate in detail the lipidome of the membrane and the outer membrane vesicle of the bacteria cells. We identified 15 lipid class/subclasses (>100 molecular species), including sphingolipid families [dihydroceramide (DHC), glycylseryl (GS) DHC, DHC-phosphoinositolphosphoryl-DHC (DHC-PIP-DHC), ethanolamine phosphorylceramide, inositol phosphorylceramide (IPC), serine phosphorylceramide, ceramide-1-phosphate, and glycosyl ceramide], phospholipids [phosphatidylethanolamine, phosphatidylinositol (PI), and phosphatidylserine], peptide lipids (GS-, S-, and G-lipids) and cholesterol sulfate, of which several have not been reported previously, or have similar structures to those found in Porphyromonas gingivalis, the periodontopathic bacterium in oral microbiota. The new DHC-PIPs-DHC lipid family is found only in B. vulgatus, which, however, lacks the PI lipid family. The galactosyl ceramide family is exclusively present in B. fragilis, which nevertheless lacks IPC and PI lipids. The lipidomes as revealed in this study demonstrate the lipid diversity among the various strains and the utility of multiple-stage mass spectrometry (MS n ) with high-resolution mass spectrometry in the structural elucidation of complex lipids.

Prevotella copri variants among a single host diverge in sphingolipid production

“…3C ), further indicating that these eight uncharacterized metabolites likely represent novel sphingolipids. Interestingly, these molecular features are not found in Bacteroides cultures, suggesting that these uncharacterized sphingolipids are unique to P. copri and therefore merit further analysis ( 15 , 17 ).…”

“…Among the Gram-negative Bacteroidota, members of the Bacteroidaceae family are well-studied for their roles in producing a diverse set of sphingolipids ( 11 , 12 , 14 , 15 ). A second family, the Rikenellaceae, including the less populous Alistipes species, have been found to produce lipids similar in structure to sphingolipids, sulfonolipids ( 16 ).…”

Universal, untargeted detection of bacteria in human tissues using spatial metabolomics

“…Single-ion images for a subset of TSMs associated with Bacteroidetes are displayed in 51 . B. fragilis is known as one of the most common bacterial species in clinical specimens and is essential for healthy gastrointestinal tract functions 52,53 while enterotoxigenic B. fragilis is thought to play a key role in the occurrence and progression of colorectal cancer 54,55 .…”

Fungal β-glucan-facilitated cross-feeding activities between Bacteroides and Bifidobacterium species

“…Currently, there are only a few publications describing any health benefits elicited by Bacteroidota (in fact some species are considered opportunistic pathogens) 40 , 41 . However, a case can be made that certain Bacteroides species represent primary glycan degraders that allow carbohydrate cross-feeding by other, beneficial members of the microbiota, such as bifidobacteria (which are not known to be able to metabolise β-glucan directly).…”