Cell surface lipopolysaccharides of different rhizobia.

Polyacrylamide gel electrophoresis profiles of various cell surface lipopolysaccharides (LPS) obtained from fast-growing strains and plasmidless mutant strains of Rhizobium ‘hedysari’, R. leguminosarum and from slow-growing Bradyrhizobium japonicum strains have been compared. Correlations were obtained by using serological techniques. Two of the fast-growing strains and one slow-growing strain employed showed several LPS with slow mobility and a few others characterized by fast mobility in the gel. Other fast-growing rhizobium strains and all the other slow-growing bradyrhizobia tested had bands widely distributed in the gels. Location of bands, in these rhizobia, did not correlate with rapidity of growth of the strains. Induced antibiotic resistance did not affect LPS composition for either the fast- or slow-growing rhizobia. The LPS composition was apparently affected by the loss of plasmids. It appears to be associated with the lack of some bands in the region ranging from 30–50 kDa. The LPS composition was also affected by the mutation in the fast mobility region. The mutant strain lacked a low molecular mass band compared with the parental strain. [1H]-NMR spectra of LPS extracts from the latter strain also revealed a signal that is missing from the spectrum of the LPS of mutant strain.