A strain of Bacillus sp. isolated from "Koso-hiryo ─ a peculiar mixture of cooked vegetablesshowed some antagonistic character and its antibiotic activity to both gram positive and negative bacteria was tested and detected by several methods.
The organism was likely to be Bacillus prausnitzii or B. tumescens and was identified as a var. of the former. Some observations were shown about the influence of nutrients on the acetoin-production of the bacteria.