Fluorescein Dyes as Bacterial Stains with Special Reference to their Use for Soil Preparations

Abstract

Erythrosin and rose bengal have been suggested in the past as bacterial stains, particularly in the case of the direct study of microorganisms in soil. The writers have made a further investigation of these two dyes and others of the same group (thirteen in all) to determine their relative merits for this purpose. It is found that practically all the deeper colored dyes of the group stain bacteria in pure culture satisfactorily; but that in the case of soil infusions some of the dyes have such an affinity for the dead organic matter as to obscure the bacteria present. Best results in the present work were obtained with rose bengal B; but it is pointed out that good staining effects may be obtained with the phloxines and erythrosins. The behavior of any one of these dyes when applied to a soil preparation varies according to the reaction of the material stained; and this is mentioned as a possible explanation as to why others have found better results with erythrosin than with rose bengal.