Fatty Material in Bacteria and Fungi Revealed by Staining Dried, Fixed Slide Preparations.

Following Hartman, who first suggested the use of Sudan black B, in place of red Sudans, as a bacterial fat stain (Hartman, 1940), Burdon, Stokes, and Kimbrough (1942a) confirmed the greater value of this dye and modified the procedure for demonstrating intracellular fatty material in bacteria by preparing, from suspensions of the organisms in alcoholic Sudan black B solution, dried films counterstained with safranine. Previously it had been thought that dried, fixed films were entirely unsuitable for fat stains (Lewis, 1941). These permanent films were regarded as an obvious improvement over the wet preparations used by earlier workers, and they were shown to be of practical aid in the classification of aerobic sporeforming bacilli (Burdon, Stokes, and Kimbrough, 1942b), but the staining method still had a number of undesirable features. Further experimentation has resulted in the development of the much superior procedure to be described here. The new method is not only simpler, requiring no more effort than a gram stain, but it is also far more rewarding, for the films now reveal clearly intracellular lipid matter that previously has not been seen or even suspected. The improved stain has increased differential value. More. over, its application, to various bacteria has resulted in certain general findings of unusual interest.