[Function of large plasmids of the plague pathogen].

Function of the largest plasmid of Yersinia pestis was studied. Assay of four strains of highly virulent Y. pestis isolated from different natural sources demonstrated that the characters of endotoxin production, sugar and alcohol fermentation, nitrate reduction as well as requirement in nutrients are mediated by no Y. pestis plasmids. On the contrary, FI and FII antigens are determined by the largest plasmid in some strains and are chromosome-mediated in others. It may well be that the genes for these antigens are comprised within the transposon-like DNA fragment.