Occurrence of an Unusual Hopanoid-containing Lipid A Among Lipopolysaccharides from Bradyrhizobium Species

Abstract

Background: Hopanoids are present in bradyrhizobial lipid A preparations. Results: Signals from hopanoid carboxyl shows strong correlation with the proton geminal to the hydroxy group of ester-linked long chain fatty acid. Conclusion: Hopanoids are covalently linked to the lipid A of Bradyrhizobium. Significance: The presence of such an unusual lipid A substituent may have a strong influence on the membrane properties of Bradyrhizobium.

Hopanoids as functional analogues of cholesterol in bacterial membranes

“…Hopanoids have been identified in the OM of diverse bacteria (29,(43)(44)(45)(46), and two recent studies have reported a covalently linked hopanoid-lipid A compound in rhizobial plantassociated bacteria (47,48). These observations suggest that hopanoid-lipid A ordering may be widespread among hopanoid-producing bacteria.…”

Hopanoid lipids: from membranes to plant–bacteria interactions

“…However, it is also possible that the relevance of hopanoids in Bradyrhizobium spp. symbioses can be attributed to the presence of an unusual lipid A structure: hopanoid-lipid A (HoLA), in which lipid A is covalently attached to an extended hopanoid polyol 113,115,116 (FIG. 4).…”

The Lipid A from Rhodopseudomonas palustris Strain BisA53 LPS Possesses a Unique Structure and Low Immunostimulant Properties

“…The latter were both ester‐linked to the primary acyl chains at positions 3′ and 2′, respectively, of the non‐reducing Glc p N3N unit. As previously mentioned, it is worth underlining that R. palustris is genetically related to the Bradyrhizobium genus, and this relationship was also clearly evident in comparisons with the recently elucidated lipid A from Bradyrhizobium strains such as BTAi1 . Indeed, besides the above described similarities concerning the sugar backbone, the presence in R. palustris strain BisA53 lipid A of an amide‐linked acyloxyacyl residue on the non‐reducing GlcN3N, on which the VLCFA 26:0(25:OAc) is appended as a secondary acyl moiety, is a structural lipid A feature in common with Bradyrhizobium strains.…”

“…Thus, R. palustris strain BisA53 has a novel lipid A structure (Figure ), in which the sugar backbone is built up of a β‐(1→6)‐linked Glc p N3N disaccharide and an α‐Gal p A residue connected to the reducing end of the Glc p N3N through an α‐(1→1) glycosidic linkage, in addition to an α‐Man p unit linked at position O4 of the non‐reducing β‐Glc p N3N residue. To date, another bacterium belonging to the Rhopseudomonas genus, namely R. viridis , as well as Rhizobiaceae (i.e., Brady ‐, Azo ‐, and Mesorhizobium genera) have been reported to be characterized by the occurrence of a Glc p N3N disaccharide backbone in place of the most common Glc p N disaccharide. Interestingly, the biosynthetic pathways of both types of lipid A sugar skeleton (namely the Glc p N and the Glc p N3N disaccharide) were proven to be similar and two enzymes, GnnA and GnnB, have been identified as being responsible for the synthesis of UDP‐ d ‐Glc p N3N from UDP‐ d ‐Glc p NAc.…”

“…As previously mentioned, it is worth underlining that R. palustris is genetically related to the Bradyrhizobium genus, and this relationship was also clearlye vident in comparisons with the recently elucidated lipid Af rom Bradyrhizobium strains such as BTAi1. [13,19] Indeed, besides the above described similarities concerning the sugar backbone, the presence in R. palustris strain BisA53 lipid Ao fa na mide-linkeda cyloxyacyl residue on the non-reducing GlcN3N, on which the VLCFA2 6:0(25:OAc) is appended as as econdary acyl moiety,i sastructurall ipid Af eature in common with Bradyrhizobium strains. Moreover,t he presence of an acetyl moiety,a ttached through an ester linkaget ot he (wÀ1) hydroxyl of the VLCFA2 6:0(25:OH), thus forming an acyloxyacyl moietya tt his position, represents af urthers imilarity among such closely relatedb acteria.…”