Functional diversity of isoprenoid lipids in Methylobacterium extorquens PA1

Abstract

Microorganisms can withstand a diversity of environmental stresses ranging from extreme temperatures to the immune defenses of multicellular organisms. The cell surface membrane serves as a first line of defense against environmental perturbations and the membrane's lipid composition is critical for stress resistance. On the one hand, the membrane must be robust enough to withstand chemical and physical challenges. On the other hand, the membrane must be fluid enough to support bioactivity. In eukaryotic organisms such as yeast, sterols play a crucial role in achieving a fluid yet mechanically robust cell surface membrane (Mouritsen & Zuckermann, 2004).

Hopanoids Confer Robustness to Physicochemical Variability in the Niche of the Plant Symbiont Bradyrhizobium diazoefficiens

“…To assess relative changes in permeability we employed an assay based on the hydrolysis of FDA to fluorescein after it diffuses into the cell (47,48). Three biological replicates of each strain were grown until till early exponential (OD 600 = 0.5).…”

The squalene route to C30 carotenoid biosynthesis and the origins of carotenoid biosynthetic pathways

“…The Δ shc mutant colonies displayed an intense red color ( Fig. 2 A ), indicating that the accumulated squalene (or its precursors) is re-directed toward carotenoid production, as observed in M. extorquens ( 7 , 13 ). Indeed, we confirmed squalene production via HpnCDE using the Δ crtN -Δ shc strain, since squalene is the precursor of hopanoids ( Fig.…”

“…4C), we observe that most of these co-occurrences have non-overlapping patterns of distribution, e.g., in the Halobacterota phylum, Halobacteria and Methanonatronarchaeia classes have C40 and C30 pathways, respectively, or Methylococcales which switched squalene and carotenoid synthesis to Sqs and C30 pathways or in Bacteroidetes presenting both C40 pathways. Conversely, other cases have both complete C30 and C40 pathways, such as some α-proteobacterial orders, although in M. extorquens only the C30 pathway is functional in normal conditions (7). Other cases, such as some Firmicutes species, present a mix of one complete (C30) and other partial (CrtH) pathway, showing the coexistence of enzymes from different pathways in the same organism.…”

“…Second, a sterol synthesis-deficient mutant of the planctomycete Gemmata obscuriglobus that accumulates squalene shows a brighter red pigmentation ( 6 ). And third, interrupting the hpnE genes in the planctomycete Planctopirus limnophila and in the α-proteobacterium Methylobacterium extorquens results in non-pigmented colonies due to the lack of carotenoid production ( 4 , 7 ). These evidences suggest the existence of a squalene route to carotenoids in nature but this possibility requires further confirmation.…”

Expanding Knowledge of Methylotrophic Capacity: Structure and Properties of the Rough-Type Lipopolysaccharide from Methylobacterium extorquens and Its Role on Membrane Resistance to Methanol

“…The combination of a simple but distinctive lipidome has been proposed to serve complementary roles in OM adaptation. 26 In this frame, a significant part of M. extorquens lipidome is occupied by the lipid A portion of the LOS (Figure 4), which is the main constituent of the OM, constantly exposed to highly mutable environmental stimuli and dangers. From a strict LPS chemistry point of view, here, we showed that M. extorquens lipid A has a non-phosphorylated tetraacylated sugar skeleton, carrying 18:0(3-OH) and 14:0(3-OH) as primary acyl chains on the distal GlcN, and a secondary 26:0(25-OH) [minor 28:0(27-OH)], in turn acylated by a novel 3-O-acetyl-butyrate residue, which to the best of our knowledge has never been found in lipid A.…”