Digoxigenin tagging of Cpn60 gene fragments by direct PCR incorporation of
digoxigenin-11-dUTP. Extraction of crude DNA from bacterial cultures by the
Instagene method (Bio-Rad Laboratories, Richmond, Calif.) was performed
according to the manufacturer’s protocol, except that instead of picking a single
colony from a blood agar plate, a disposable inoculating loop was used to sweep
across the culture plate to harvest multiple colonies. The PCR protocol was as
described in reference 16. The primers for PCR were those described in the
following section. The digoxigenin-labeled Cpn60 PCR products, without purification,
were diluted 1:100 in hybridization buffer (53 SSC [13 SSC is 0.15 M
NaCl and 0.015 M sodium citrate], 50% formamide, 2% Boehringer Mannheim
blocking reagent, 0.1% N-lauryl sarcosine, 0.02% SDS and used directly for
reverse checkerboard hybridization.