Characterization of root-nodule bacteria indigenous in the salt-affected soils of Egypt by lipopolysaccharide,protein and plasmid profiles

Some characteristics of thirty isolates of root-nodule bacteria, indigenous in the salt-affected soil of Egypt, were studied. To recognize different isolates of these bacteria, the electrophoretic pattern of plasmids and of whole cell lipopolysaccharides (LPS) and proteins were analysed and compared using agarose gel electrophoresis (AGE) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), respectively. The bacteria showed patterns of LPS, protein and plasmid which varied among isolates of different plant species as among isolates of a single plant species. Based on LPS and protein profile analysis, isolates from root-nodules of broadbean and lupin plants were more diverse than isolates from root-nodules of berseem plant. Root-nodule bacteria of lupin and berseem were also less diverse than root-nodule bacteria of broadbean when compared on the basis of plasmid profiles. This result indicate that root-nodule bacteria of broadbean may have higher surviving ability in the salt-affected soil. Most isolates of the root-nodule bacteria synthesized specific LPS (smooth, ladder-like type) and protein, which were different from LPS and protein of other well-known (recognized) Rhizobium species. These specific forms of LPS and protein could be a prerequisite for the bacterial isolates to tolerate salt stress conditions of the salt-affected soils.