Pyrosequencing analysis of the microbiota of kusaya gravy obtained from Izu Islands

Kusaya is a salted, dried fish product traditionally produced on the Izu Islands in Japan. Fish are added to kusaya gravy repeatedly and intermittently, and used over several hundred years, which makes unique microbiota and unique flavors. In this study, we performed a metagenomic analysis to compare the composition of the microbiota of kusaya gravy between different islands. Twenty samples obtained from a total of 13 manufacturers on three islands (Hachijojima, Niijima, and Oshima Islands) were analyzed. The statistical analysis revealed that the microbiota in kusaya gravy maintain a stable composition regardless of the production steps, and that the microbiota are characteristic to the particular islands. The bacterial taxa common to all of the samples were not necessarily the dominant ones. On the other hand, the genera Halanaerobium and Tissierella were found to be characteristic to the microbiota of one or two islands. Because these genera are known to be present in the natural environment, it is likely that the bacterial strains peculiar to an island had colonized kusaya gravy for many years. The results of this study revealed an influence of geographical conditions on the microbiota in fermented food.