Biosynthesis of trehalose from maltooligosaccharides in Rhizobia

Abstract

Previously, the enzymes for trehalose synthesis that are present in Escherichia coli were demonstrated in Bradyrhizobium japonicum and B. elkanii. An alternative mechanism recently reported for the synthesis of trehalose from maltooligosaccharides was considered based on the fact that high concentrations of sugars in liquid culture stimulated the accumulation of trehalose. An assay for the synthesis of trehalose from maltooligosaccharides using crude, gel-filtered protein preparations was developed. Analysis of a variety of the Rhizobiaceae indicates that the "maltooligosaccharide mechanism" is present in B. japonicum, B. elkanii, Rhizobium sp. NGR234, Sinorhizobium meliloti, R. tropici A, R. leguminosarum bv viciae, R. l. bv trifolii, and Azorhizobium caulinodans. Synthesis of trehalose from maltooligosaccharide could not be detected in R. tropici B or R. etli. With these two exceptions, it is suggested that rhizobia have two mechanisms for the biosynthesis of trehalose.Key words: maltooligosyl trehalose synthase, maltooligosyl trehalose trehalohydrolase, symbiotic nitrogen fixation.