Ether- and Ester-Bound iso -Diabolic Acid and Other Lipids in Members of Acidobacteria Subdivision 4

Abstract

e Recently, iso-diabolic acid (13,16-dimethyl octacosanedioic acid) has been identified as a major membrane-spanning lipid of subdivisions 1 and 3 of the Acidobacteria, a highly diverse phylum within the Bacteria. This finding pointed to the Acidobacteria as a potential source for the bacterial glycerol dialkyl glycerol tetraethers that occur ubiquitously in peat, soil, lakes, and hot springs. Here, we examined the lipid composition of seven phylogenetically divergent strains of subdivision 4 of the Acidobacteria, a bacterial group that is commonly encountered in soil. Acid hydrolysis of total cell material released iso-diabolic acid derivatives in substantial quantities (11 to 48% of all fatty acids). In contrast to subdivisions 1 and 3 of the Acidobacteria, 6 out of the 7 species of subdivision 4 (excepting "Candidatus Chloracidobacterium thermophilum") contained iso-diabolic acid ether bound to a glycerol in larger fractional abundance than iso-diabolic acid itself. This is in agreement with the analysis of intact polar lipids (IPLs) by high-performance liquid chromatography-mass spectrometry (HPLC-MS), which showed the dominance of mixed ether-ester glycerides. iso-Diabolic acid-containing IPLs were not identified, because these IPLs are not released with a Bligh-Dyer extraction, as observed before when studying lipid compositions of subdivisions 1 and 3 of the Acidobacteria. The presence of ether bonds in the membrane lipids does not seem to be an adaptation to temperature, because the five mesophilic isolates contained a larger amount of ether lipids than the thermophile "Ca. Chloracidobacterium thermophilum." Furthermore, experiments with Pyrinomonas methylaliphatogenes did not reveal a major influence of growth temperature over the 50 to 69°C range.

Mono- and Dialkyl Glycerol Ether Lipids in Anaerobic Bacteria: Biosynthetic Insights from the Mesophilic Sulfate Reducer Desulfatibacillum alkenivorans PF2803 T

“…1). Since then, diether or tetraether or mixed ether/ester lipids have been reported in an increasing number of bacterial species, including few mesophilic ones (10,20,46). Among SRB, diether lipids have thus far been reported only from thermophilic species (16,19) whereas monoalkyl/monoacyl phospholipids have also been identified in the mesophilic species Desulfosarcina variabilis and Desulforhabdus amnigenus (7) (Fig.…”

“…This hypothesis on the stereochemistry of the glycerol backbone further relies on the sn-1,2 stereoconfiguration of the glycerol moieties of branched tetraether lipids (brGDGTs) (Fig. 1) present in soils and peats (15) and likely produced by Acidobacteria (10,46).…”

Abundant Trimethylornithine Lipids and Specific Gene Sequences Are Indicative of Planctomycete Importance at the Oxic/Anoxic Interface in Sphagnum-Dominated Northern Wetlands

“…Acidobacteria are more abundant at the oxic/anoxic interface of the Saxnäs Mosse peat bog (Fig. 5) and could potentially also be a source of TMO IPLs; however, previous studies analyzed the IPL composition of many acidobacterial species falling in subgroups 1, 3, 4, and 23 (60)(61)(62) and did not detect TMO IPLs. The 16S rRNA gene sequences retrieved in our analysis of the Saxnäs peat bog were closely related to Acidobacteria subgroups 1, 2, and 13 (see Fig.…”

“…5). Difficulty in extracting the membrane lipids of acidobacteria (60,61), which represent 30 to 60% of all pyrosequencing reads in Saxnäs Mosse peat (Fig. 5A), could also result in underrepresentation of acidobacterial IPL contribution.…”

A refined paleotemperature calibration for New Zealand limnic environments using differentiation of branched glycerol dialkyl glycerol tetraether (brGDGT) sources

“…Bacterial branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are ubiquitous in soils, peats and coals as well as in lacustrine and coastal‐marine sediments, have a strong potential for paleotemperature reconstruction (Hopmans et al ., ; Weijers et al ., ; Blaga et al ., ; Fry et al ., ; Tierney et al ., ; Peterse et al ., ; Fietz et al ., ; Loomis et al ., ; Anderson et al ., ). brGDGTs were initially proposed to derive from anaerobic bacteria living in soils and peat bogs (Weijers et al ., ) with recent evidence derived from culture‐dependent approaches indicating that members of the Acidobacteria may constitute a significant biological source of brGDGTs in natural environments (Sinninghe Damsté et al ., , ).…”