A rapid and sensitive method of detection of the sake spoilage microorganisms hiochi bacteria was developed. The hiochi bacterial common antigen (hb-CA) was identified using a monoclonal antibody (MAb) and its gene was cloned. The nucleotide sequences of the hb-CA gene from four standard strains of hiochi bacteria were then determined. Two polymerase chain reaction (PCR) primers for use in the detection of hiochi bacteria were designed by homology analysis of these sequences. When genomic DNA from the hetero-fermentative true hiochi bacillus (he-T) Lactobacillus fructivorans HI was amplified by PCR using this set of primers and electrophoretically analyzed, a PCR product could be detected when as little as 10 fg of genomic DNA, which corresponds to the amount of DNA in a single cell, had been used. When he-T L. fructivorans H1 was inoculated into 300 ml of pasteurized sake, the cells recovered by filtration, and the DNA analyzed by this method, the detection limit was found to be about 10 cells. This method is much faster than the standard culture method. This PCR technique is a rapid and highly sensitive method of detection of hiochi bacteria which is applicable to quality control of sake. The results of a homology search performed using the deduced amino acid sequence of this common antigen suggest that this antigen is the hiochi bacterial elongation factor Tu (EF-Tu).