GLYCOCONJUGATE AND LIPID COMPONENTS OF RHIZOBIUM-HEDYSARI IS123, A ROOT-NODULE SYMBIONT OF THE STRESS-TOLERANT LEGUME HEDYSARUM-CORONARIUM

We have examined the diversity of glycoconjugates and cellular lipids of Rhizobium ''hedysari'' IS123, a bacterial symbiont that specificall y nodulates the drought-tolerant forage legume Hedysarum coronarium. I S123 develops a complete capsule consisting of a loose fibrillar netwo rk of ruthenium-red-staining acidic polymers and produces two differen t exopolysaccharides (EPS). EPS-A contains glucose, galactose, mannose , and a noncarbohydrate substitution tentatively identified as a lacty l ester. The composition of EPS-B, which includes glucose and galactos e, as well as O-acetyl, pyruvyl, and succinyl substituents, is very si milar to that of the EPS-II described in Rhizobium meliloti. IS123 als o makes an O-acetylated heterooligosaccharide and unsubstituted beta-1 ,2-glucans. The cellular fatty acid composition of IS123 is dominated by 18:1 and also includes 14:0, 16:0, 16:1, 3OH-16:0, 17:0 Delta, 18:0 , 3OH-18:0, and 19:0 Delta. Phospholipids of IS123 include phosphatidy lethanolamine, N-methyl phosphatidylethanolamine, N,N-dimethyl phospha tidylethanol amine, phosphatidylcholine, and phosphatidylglycerol.