The present invention addresses the problem of acquiring a temperature-sensitive Bacillus natto that has normal spore-forming ability in a temperature zone normally used in a liquid culture for acquiring a Bacillus natto starter for inoculation but that has reduced spore-forming ability in a temperature zone normally used in natto fermentation, and of providing a natto having a low content of natto bacterial spores using the Bacillus natto, without such problems as fermentation defects or contamination with unwanted bacteria, and through use of an existing process and equipment. Through the present invention, a variant of Bacillus natto (Bacillus subtilis var. natto) having the properties (A) through (C) below is provided. (A) In a single colony of the Bacillus natto variant grown by culturing for 48 hours at a vapor-phase temperature of 49°C in a selective solid medium containing biotin, the area of a region in which the Munsell color system hue is yellow (Y), the lightness is 9 or higher, and the chroma is 2 or lower in the color specification thereof is 20% or less, where the total area of the surface of the single colony is 100%. (B) When culturing is performed at a medium temperature of 37°C in a spore-forming medium, the spore count of the Bacillus natto variant is 1×107 spores/mL or greater. (C) When soybeans or cooked soybeans are inoculated with the Bacillus natto variant to give a Bacillus natto spore count of 5×103 per 1 g and the temperature of the beans is maintained in the range of 40-53°C, a natto can be produced that has good stringiness and aroma peculiar to natto, and that has a Bacillus natto spore count of 5×105 or less per 1 g of the natto.Le problème à la base de la présente invention concerne l'acquisition d'un bacillus natto sensible à la température qui présente une aptitude normale à la formation de spores dans une zone de température normalement utilisée dans une culture liquide pour acquérir un initiateur de bacillus natto pour l'inoculat
