Altered cell surface hydrophobicity of lipopolysaccharide-deficient mutantof Bradyrhizobium japonicum

The authors previously isolated a lipopolysaccharide (LPS) deficient Tn5-mu tant of Bradyrhizobium japonicum, and subsequently isolated the LPS gene re gion. In this study the LPS deficiency of B. japonicum was studied in terms of its cell surface characteristics. By monitoring the kinetics of the par tition with hexadecane the LPS-mutant was found to be far more hydrophobic than the wild type strain; the partition coefficients were 3.19 min(-1) for the mutant, as compared with only 1.40 min(-1) for the wild type. When the mutant was transformed with the cloned LPS gene, the transformant regained the wild type phenotypes, including the cell surface hydrophobicity (CSH) and LPS profile. A polyacrylamide gel electrophoretic analysis of LPS demon strated that the O-antigenic part of LPS was completely absent in the mutan t. The LPS-mutant of B. japonicum was visually distinguishable from the wil d type after a simple centrifugation of the cells. (C) 2000 Elsevier Scienc e B.V. All rights reserved.