[Some observations on the mechanism of bactericidal activity of Tween 80 on mycobacteria]

In 0.1% Tween 80 aqueous solution or in 0.1% Tween 80-containing saline (0.9% NaCl aqueous solution), Mycobacterium smegmatis strain Jucho bacteria were alive for 3 days, whereas, in 0.1% Tween 80-containing phosphate buffer solution (pH 7.1), the bacteria died rapidly. Since it was shown previously that M. smegmatis is one of the mycobacteria most susceptible to Tween 80 (Tsukamura, M.: Kekkaku 63: 695-699, 1988), the 0.1% Tween 80 aqueous solution or 0.1% Tween 80-containing saline may be used for suspending mycobacteria in order to prevent the clumping. Incorporation of 32P-ortho-phosphate to the nucleic acid fraction was most markedly inhibited by the presence of 0.5% Tween 80 in 0.067 M phosphate buffer solution (pH 7.1). The finding shows that Tween 80 inhibits directly or indirectly the synthesis of nucleic acids. Tween 80 was not bactericidal in an aqueous solution but acted bactericidally in the co-existence of phosphate, and such bactericidal activity was completely diminished by adding an ammoniacal nitrogen compound (Tsukamura, M.: Medicine and Biology (Tokyo) 96: 159-161, 1978). These findings suggest that Tween 80 does not simply act as a detergent but interferes with some metabolic way in the synthesis of nucleic acids.