FIG. 5.

mRNA expression in passage 5 serotype M49-derived stabilized small and typical colony isolates. mRNA was obtained from late-logarithmic-phase cultures inoculated with passage 5 typical and stabilized small isolates when at least 50% the plated colonies had reverted to a typical large-colony phenotype. The lanes labelled “small” denote mRNA isolated from reverted stabilized small colonies. Total RNA concentration recovered was determined by spectrophotometric measurement at OD₂₆₀, appropriate dilutions were made (indicated above each lane), and even loading of the lanes was confirmed by visual inspection of ethidium bromide-stained gels prior to transfer to membranes. The RNA gels were subsequently Northern blotted, and the binding of specific DIG-labeled PCR probes (indicated at the bottom of each blot) was determined by CSPD development followed by autoradiography. The bands detected by the individual probes were consistent with reported mRNA sizes (45). Fresh RNA was prepared for each blot. The autoradiograms shown above represent the consistent results obtained for the individual typical and atypical isolates at passage 5. Similar results were obtained with a second independently derived atypical small and typical isolate at passage 9.