Applicability of a combined staining method with fluorochromes for the visualization of microbial cells in a soil thin section

Staining of microbial cells in a soil thin section provides useful informat ion about the role of soil as an ecological niche by relating the in situ d istribution of microorganisms to the state of pores under undisturbed condi tions. For technical improvement, we developed a procedure consisting of a combined staining method with 5-sulfofluorescein diacetate (SFDA), a metabo lic type fluorochrome, and magnesium salt of 1-anilino-8-naphthalene sulfon ic acid (Mg-ANS), an adsorption type fluorochrome, in order to detect and d ifferentiate the living microbial cells from the dead ones in a single soil thin section. Using images under a fluorescence microscope, me also examin ed the applicability of SFDA for staining microbial cells embedded in soil thin sections, which had seldom been attempted, Through this study, we conf irmed the following facts: i) combined staining with SFDA and Mg-ANS can be achieved without major modification of the general procedure for thin sect ion preparation, ii) staining with SFDA can be applied to soil thin section s, and iii) detection of in situ distribution and differential identificati on of the living and dead microbial cells may be possible by the proposed c ombined staining method.