N-glyceroyl alkylamine phosphoglycolipids dominate the lipidome of several Bacillota bacteria

Abstract

Elucidation of the membrane lipid composition of bacteria can help to better understand how bacterial cells interact with their surroundings, adapt to environmental stress, and resist antimicrobial agents. Here we describe for the first time the detection of a wide array of N-glyceroyl alkylamine phosphoglycolipids (NGAPs) in a range of Bacillota bacteria (formerly Firmicutes). Bacillota includes a diverse range of bacteria that are typically highly resistant to harsh conditions such as heat, radiation, and pH, allowing the bacteria to survive in unfavorable environments. In 9 out 18 investigated strains of Bacillota, spread across 5 orders (Thermoanaerobacterales, Thermosediminibacterales, Eubacteriales, Halanaerobiales, and Sulfobacillia) mild acid hydrolysis released N-glyceroyl alkylamines (NGAs), which were detectable by gas chromatography–mass spectrometry (GC–MS) during routine fatty acid analysis. One strain, Moorella thermoacetica was found to produce long-chain NGAs (C₃₀-C₃₂), which are postulated to have isodiabolic acid-like structures. A wide variety of intact polar NGAPs were identified using ultra-high pressure liquid chromatography high resolution multi-stage mass spectrometry (UHPLC-HRMSⁿ). These include many previously undescribed lipids with a variety of sugar moieties and glycerol-bound core lipid moieties, including ether-bound components and alkyl 1,2-diols. The NGAPs constituted the majority of the intact polar lipid composition of these strains and presumably contribute to their tough cell membranes. The presence of NGAs in Bacillota appears to be associated with thermophilia. Both the hydrolysis-derived NGAs and intact polar NGAPs have potential to be biomarkers for extremophilic and, in particular, thermophilic bacteria.