Biochemical characteristics of typhus group rickettsiae with special attention to the Rickettsia prowazekii strains isolated from flying squirrels

Abstract

Six strains of R. prowazekii, 2 derived from human infections and 4 isolated from flying squirrels, 2 strains of R. typhi, and the single available strain of R. canada, were characterized by several biochemical procedures. The electrophoretic patterns on polyacrylamide gels of rickettsial proteins solubilized by sodium dodecyl sulfate revealed several species differences, but strains of the same species appeared to have identical patterns. Cytoplasmic fractions of the rickettsiae were examined for enzymatic activities and for polyacrylamide gel isoelectric focusing patterns. Some species differences were encountered in the activities or ratios of activities of glutamate-oxaloacetate transaminase, glutamate dehydrogenase, and malate dehydrogenase. When polyacrylamide gels were stained for malate dehydrogenase after electrophoresis, a single band became apparent with single extracts or mixtures of 2 strains of R. prowazekii, but 2 bands were seen with mixtures of a strain of R. prowazekii and 1 of R. typhi. The isoelectric focusing patterns of the soluble proteins revealed numerous species differences, especially between R. canada and the other 2 species, and a few differences among the strains of R. prowazekii. The patterns of the 2 human strains, Breinl and E(R), differed in at least 1 location, and both differed from the flying squirrel strains in the displacement of 1 band. One of the flying squirrel strains, GvF-16, contained a protein band not seen in the other 5 strains. Despite these minor differences, a striking similarity was revealed by all the biochemical tests performed between the R. prowazekii strains of human and flying squirrel origin.