Rapid degradation of ribosomal RNA in Pasteurella septica induced by specific antiserum

Abstract

Antibody, transferrin and complement, acting together, directly interfere with the biochemistry of Pasteurella septica effecting an inhibition of RNA accumulation and the cessation of bacterial growth. This communication describes the fate of ribosomal RNA in antiserum inhibited cells. P. septica RNA was prelabelled with 32P or [ 14C] uracil, the organisms resuspended in unlabelled horse serum and antiserum added. The label remained in the RNA for up to 45 min after the addition of antiserum but was lost very rapidly thereafter. By the 90th min, 80–90% had been lost, this loss being reflected by the appearance of labelled material in the serum. Sucrose gradient analysis showed that the ribosomes were lost from such inhibited cells and that the ribosomal RNA was broken down before it was lost from the cells or even released from the ribosomal particles. Addition of haematin to the system prevented both the inhibition of bacterial growth and the subsequent breakdown of RNA. A similar degradation of ribosomal RNA was seen when antiserum was added to P. septica growing in rabbit serum, although in this case, antiserum produced bacteriostasis instead of the lethal effect seen in horse serum.