Study of the S-Layer Protein in Legionella pneumophila and Listeria monocytogenes

The presence of surface layer was detected in each of Legionella pneumphila (gram negative) and Listeria monocytogenes (gram positive) by extraction of S-layer proteins then separated by using sodium dodecyle sulphate poly acrylamide gel electrophorasis (SDS-PAGE). Five proteins bands appeared for both types of bacteria.
The freezing effect on the S-layer protein of L. monocytogenes was studied by exposure to low temperature at -20C for three months. Six protein bands were detected,, as well as their differences in approximate molecular weights for the freezing isolate in comparison with non-frozen isolate.