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In order to investigate the hydrogen-bonding interactions between Escherichia coli ribonuclease HI and the 2'-hydroxyl functions of the substrate, oligonucleotide duplexes containing 2'-amino-2'-deoxyuridine or 2'-fluoro-2'-deoxyuridine at a specific site were used, and their affinities for the enzyme were determined by kinetic analyses. The results indicate that the hydroxyl groups of the nueleoside 3'-adjacent to the cleaved phosphodiester linkage and the second nucleoside 5' to the cleaved phosphodiester act as both a proton donor and an acceptor and as a proton acceptor, respectively, in the enzyme-substrate complex. A molecular model was constructed using the interactions derived from the results.

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The colony hybridization (CH) method as a rapid method for detecting Legionella spp. was compared with the conventional culture method. In the comparison of colony count in which a suspension of L. pneumophila was examined, a positive correlation was shown between the results by both methods. The regression line was Y=0.85+1.34X and the correlation coefficient was 0.95. The maximum number of detectable colonies on the plate was 144 colony forming units, although there was a tendency for the CH data to give slightly lower counts than those of the culture method. The detection time in the CH method was half of that in the culture method, and the final result was obtained within 4 or 5 d. In addition the results by the CH method were rarely influenced by other contaminating microorganisms, since the transfer of colonies was performed at the initial stage of culture.

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