The cellular lipids of Romboutsia

Area of Science:

• Microbiology
• Lipidomics
• Bacterial Taxonomy

Background:

• The genus Romboutsia represents a newly described group of bacteria.
• Understanding the lipid composition of Romboutsia is crucial for its taxonomic classification and understanding its biology.
• Comparison with related genera like Clostridium can highlight unique evolutionary or functional adaptations.

Purpose of the Study:

• To characterize the lipidome of three Romboutsia species: Romboutsia lituseburensis, Romboutsia ilealis, and Romboutsia sp. strain FRIFI.
• To identify common and unique lipids across these species.
• To compare the lipid profiles of Romboutsia with those of closely related bacteria, particularly Clostridium difficile.

Main Methods:

• Two-dimensional thin-layer chromatography (2D-TLC) was employed for lipid separation.
• Liquid chromatography/mass spectrometry (LC/MS) was utilized for lipid identification and characterization.
• 16S rRNA gene sequencing was used to confirm the phylogenetic relationship between Romboutsia and Clostridium species.

Main Results:

• All three Romboutsia species contained phosphatidylglycerol (PG), cardiolipin, and phosphatidic acid.
• Lysyl-PG was found in R. lituseburensis and strain FRIFI. Polyprenyl-phosphates were present in all isolates.
• Mono-, di-, and tri-hexosyldiacylglycerols were common; tetrahexosyl-diacylglycerol and acylated variants were found in specific strains.
• A significant finding was the absence of alk-1-enyl ether lipids (plasmalogens) in Romboutsia, contrasting with Clostridium species.

Conclusions:

• The lipidome of Romboutsia species is characterized by specific phospholipids and glycolipids, with variations among strains.
• The absence of plasmalogens in Romboutsia is a key distinguishing feature compared to the related genus Clostridium.
• These lipidomic differences contribute to the taxonomic distinctiveness of the Romboutsia genus.