STRUCTURAL DETERMINATION OF SYMBIOTIC NODULATION FACTORS FROM THE BROAD-HOST-RANGE RHIZOBIUM SPECIES NGR234

Nod factors are secreted lipo-oligosaccharides produced by symbiotic n itrogen-fixing Rhizobium bacteria that induce nodule formation on the roots of host leguminous plants. Two biologically active fractions (No dNGR(A) and NodNGR) were isolated by reversed-phase HPLC from the cult ure supernatant of a Nod factor overproducing strain of Rhizobium sp. NGR234, NodNGR(A) and NodNGR(B) are heterogeneous mixtures of N-acylat ed 2-O-methylfucosylated chitomers, in which the fucosyl residue may b e either 3-sulfated (NodNGR(A)), or 4-O-acetylated or nonsubstituted ( NodNGR(B)). Structurally analogous series of compounds occur with eith er N-vaccenic (C18:1) or N-palmitic (C16:0) substituents. The presence of 6-O-carbamoyl groups on the GlcNMeAcyl residue occurs on some mole cules, while others are di-O-carbamoylated.