Subdivision of daughter strains of bacille Calmette-Guérin (BCG) according to secreted protein patterns

Abstract

In order to identify proteins secreted by live organisms, daughter strains of the Bacillus Calmette-Guérin (BCG) were grown for 4-7 d in a defined medium containing [35S]methionine. Secreted components were then separated by polyacrylamide gel electrophoresis under both denaturing and non-denaturing conditions, and analysed by autoradiography and in an Ambis beta-scanner. The results indicate that BCG daughter strains can be subdivided into two groups according to their secretion of a 46 kDa protein dimer consisting of two similar 23 kDa subunits. High-producer strains (Japanese, Brazilian and Russian) secrete very large quantities of this material, which constitutes approximately 23% of all secreted protein. These findings correlate with earlier studies in which degradation products of the protein dimer may have been identified, and with the data from patterns of cell wall lipids.