ALTERATION OF LIPOPOLYSACCHARIDE AND PROTEIN PROFILES IN SDS-PAGE OF RHIZOBIA BY OSMOTIC AND HEAT-STRESS

The effects of osmotic and heat stress on lipopolysaccharides and prot eins of rhizobia isolated from the root nodules of leguminous trees gr own in semi-arid soils of the Sudan, and of agricultural legumes grown in salt-affected soil of Egypt, were determined by SDS-PAGE. The rhiz obia were of three types: (1) sensitive strains, unable to grow in 3% (w/v) NaCl in yeast mannitol medium; (2) tolerant strains which could grow in 3% (w/v) NaCl; and (3) halophytic strains which grew with 3 to 10% (w/v) NaCl. The sensitive strains changed their gel pattern or th e amount of lipopolysaccharide they synthesized when grown in 10% (w/v ) NaCl. The tolerant and halophytic strains often modified their lipop olysaccharides in 3% NaCl, which was evident by a shift in the banding patterns towards longer chain length. Similar effects were observed i n cells incubated with sucrose and, to a lesser extent, in cells incub ated at growth temperatures near the recorded maximum temperature for growth. The stress-induced changes in lipopolysaccharides were not ass ociated with specific banding patterns of the lipopolysaccharides. Dur ing incubation in medium containing elevated concentrations of NaCl or sucrose, the protein patterns of the rhizobia were also changed. A pr otein with relative mobility of 65 kDa appeared during temperature str ess. The maximum growth temperature of the Sudanese rhizobia were up t o 44.2-degrees-C.