Fluorescein-labeled beta-glucosidase as a bacterial stain.

Fluorescein isothiocyanate-labeled beta-glucosidase was used as a simple staining reagent with selected gram-positive and gram-negative organisms. Staining in situ appeared to be dependent on the presence of accessible glycosidic-type linkages in the bacterial cell wall. Extensive wall damage or lysis did not occur when stained cells were suspended in washing and mounting solutions. The apparent specificity of labeled enzyme for wall substance was tested by blocking reactions, staining of isolated cell walls, and failure to stain substances lacking appropriate glycosidic linkages. Severe cell wall lesions were produced after prolonged contact with labeled enzyme, and this phenomenon may also be related to staining specificity. Gram-negative organisms and spores were poorly stained unless protected glycopeptide substrate was previously exposed by treatment of cells with thioglycolic acid or dilute alkaline sodium hypochlorite solution. A potential for staining tissues and cell lines may also exist. Some possible applications of labeled enzymes are briefly discussed.

Direct fluorescent labeling of microorganisms as a possible life-detection technique.

Microorganisms and selected proteinaceous substances were directly tagged with fluorescein isothiocyanate. This approach suggested a possible application for detection of extraterrestrial life. A stable and apparently specific linkage was formed with protein, and nonprotein substances were readily destained. Soil and atmospheric debris did not exhibit any significant affinity for the dye.