Comparative analysis of bacterial communities in traditional fermented food: Nezushi from Gifu Prefecture and izushi-style narezushi from across Japan

Narezushi is a traditional Japanese fermented food made from fish and rice. Nezushi is a regional variety of izushi-style narezushi produced in the Hida (Gero) and Oku-Mino (Gujo) regions of Gifu Prefecture. In this study, nezushi was analyzed to clarify its bacterial communities using both culture-dependent and culture-independent approaches. Nezushi (Gero) was dominated almost exclusively by Latilactobacillus sakei, whereas nezushi (Gujo) showed greater diversity with Latilactobacillus sakei and Leuconostoc lactis. Izushi (Tokachi) closely resembled nezushi (Gero), while izushi (Ishikari) resembled nezushi (Gujo). In contrast, kabura‑zushi (Kanazawa) exhibited a distinct community dominated by Leuconostoc spp. These results indicate that psychrotrophic lactic acid bacteria, primarily Latilactobacillus sakei and Leuconostoc spp., drive fermentation in izushi‑style narezushi, while regional processing conditions shape microbial composition. This study provides the first microbiological characterization of nezushi, revealing previously unrecognized features of its fermentation ecology.