Action of Stains on Living Bacteria

Abstract

In studies on the streptococci and lactobacilli now in progress it became necessary to carefully examine the methods used in staining bacteria. The staining technique of the bacteriologist, for the most part, has advanced very little beyond that employed by the early workers. Perhaps Dobell 1 did more to point out certain fallacies of these methods than any other, yet his work is rarely quoted. The seemingly accepted technique is to dry on a slide the film of liquid containing the organism. After flaming, aqueous solutions of dye are flooded over the films. The delicate cytoplasm of the cell must necessarily be somewhat distorted by such methods. There are some descriptions of vital staining but generally little has been accomplished. We attempted to study the subject, using, as suggested by Dobell, a very large cell. In this case a Gram-positive organism from the gut of a guinea pig was used.

The method of staining was to add a water solution of the stain directly to either a broth or saline suspension of the organisms. The stained bacteria were examined in both wet and dry preparations. Certain stains revealed granules of varying arrangement and size within the cell. From the work of Guillermond 2 these were in all probability metachromatic granules. (Table I.) Dobell's results would agree since he says, “In my experience, only non-living structures in the cells (metachromatic granules, etc.) can be stained during life. But doubtless much depends on the stain itself!”

Gay and Clark 3 suggested that “vital” staining may really only represent a stage in a process of injury by the stain. In an attempt to test the possibility of injury to the cell experiments were designed to determine the toxicity of the various stains.