Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 8/28/1996
Publication Date: N/A
Technical Abstract: A unique glucan has been isolated from a recombinant strain of a Rhizobium meliloti TY7, a cyclic beta-1,2 glucan mutant carrying a locus specifying beta-1,3; 1,6 glucan synthesis from Bradyrhizobium japonicum USDA110. Unlike those cyclic glucans previously isolated from Rhizobium meliloti or Bradyrhizobium japonicum this molecule contains neither phosphoglycerol nor rphosphocholine substituents, respectively. Two dimensional 13C-1H HSQC NM spectroscopy and methylation analysis showed that this DP=12 cyclic glucan structure is composed of ten 1,3 linked; one non-reducing terminal and one 1,3,6-linked glucopyranose units, all of which are in the beta configuration. Two dimensional 13C-1H HMBC NMR demonstrated that the cyclic structure (1) had a branch at a C6-OH containing two beta-1,3 linked glucopyranose units. Chemical modification of I via two consecutive Smith degradation sequences produced the unbranched parent compound cyclolaminarinose, (mass spec. M+5Na 1735, DP=10) whose 13C NMR spectrum exhibited six degenerate resonances corresponding to a ten fold center of symmetry. Synthesis of this newly described cyclic beta-glucan in R. meliloti ndvB mutant restored the symbiotic and hypoosmotic adaptation characteristics of the R. meliloti wild type strain.