Dominance of mixed ether/ester, intact polar membrane lipids in five species of the order Rubrobacterales: Another group of bacteria not obeying the “lipid divide”
Sinninghe Damsté, J.S; Rijpstra, W.I.C.; Huber, K.J.; Albuquerque, L.; Egas, C.; Bale, N. (2023). Dominance of mixed ether/ester, intact polar membrane lipids in five species of the order Rubrobacterales: Another group of bacteria not obeying the “lipid divide”. Syst. Appl. Microbiol. 46(2): 126404. https://dx.doi.org/10.1016/j.syapm.2023.126404 In: Systematic and Applied Microbiology. Elsevier: Jena. ISSN 0723-2020; e-ISSN 1618-0984, more |   |
| Keywords | Rubrobacter Suzuki, Collins, Iijima & Komagata, 1988 [WoRMS]; Rubrobacter bracarensis; Rubrobacter calidifluminis; Rubrobacter naiadicus; Rubrobacter radiotolerans; Rubrobacter xylanophilus; Rubrobacterales [WoRMS]
| | Author keywords | Rubrobacterales; 1-O-alkyl glycerol ether lipids; Intact polar lipids; ?-cyclohexyl fatty acids; (?-4)-methyl fatty acids; Rubrobacter radiotolerans; R. xylanophilus; R. bracarensis; R. calidifluminis; R. naiadicus |
| Authors | | Top | - Sinninghe Damsté, J.S, more
- Rijpstra, W.I.C., more
- Huber, K.J.
| - Albuquerque, L.
- Egas, C.
- Bale, N., more
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| Abstract | The composition of the core lipids and intact polar lipids (IPLs) of five Rubrobacter species was examined. Methylated (ω-4) fatty acids (FAs) characterized the core lipids of Rubrobacter radiotolerans, R. xylanophilus and R. bracarensis. In contrast, R. calidifluminis and R. naiadicus lacked ω-4 methyl FAs but instead contained abundant (i.e., 34–41 % of the core lipids) ω-cyclohexyl FAs not reported before in the order Rubrobacterales. Their genomes contained an almost complete operon encoding proteins enabling production of cyclohexane carboxylic acid CoA thioester, which acts as a building block for ω-cyclohexyl FAs in other bacteria. Hence, the most plausible explanation for the biosynthesis of these cyclic FAs in R. calidifluminis and R. naiadicus is a recent acquisition of this operon. All strains contained 1-O-alkyl glycerol ether lipids in abundance (up to 46 % of the core lipids), in line with the dominance (>90 %) of mixed ether/ester IPLs with a variety of polar headgroups. The IPL head group distribution of R. calidifluminis and R. naiadicus differed, e.g. they lacked a novel IPL tentatively assigned as phosphothreoninol. The genomes of all five Rubrobacter species contained a putative operon encoding the synthesis of the 1-O-alkyl glycerol phosphate, the presumed building block of mixed ether/ester IPLs, which shows some resemblance with an operon enabling ether lipid production in various other aerobic bacteria but requires more study. The uncommon dominance of mixed ether/ester IPLs in Rubrobacter species exemplifies our recent growing awareness that the lipid divide between archaea and bacteria/eukaryotes is not as clear cut as previously thought. |
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