Modified pyrogallol-initiated immunogold-silver enhancement technique applicable to prokaryotes

A modified immunogold-silver enhancement technique that was designed to reduce the nonspecific granular background staining, particularly for application on prokaryotic organisms, is reported. Aerial oxidation of pyrogallol contained in the commercial silver enhancer solution was effectively controlled during storage and in the reaction mixture. A combination of strategies such as storing the reagent under argon, modifying it using 0.5% (w/v) anhydrous sodium sulfite, reducing the concentration of silver ions in the reaction mixture and limiting the length of the silver enhancement reaction considerably reduced the granular background staining. The modified technique was demonstrated on the bacterium Xanthomonas campestris pv. malvacearum (Smith) Dye. A 7-min silver enhancement step produced little background staining, while optimal silver intensification of the bacterium pre-treated with the immunogold label was achieved.