Analysis of bacterial community structure in Saba-Narezushi (Narezushi of Mackerel) by 16S rRNA gene clone library.

Narezushi, a derivation of sushi, is a traditional Japanese food made by fermenting salted fish meat and cooked rice together. In this study, the microbial diversity of saba-narezushi (narezushi of mackerel, Scomber japonicus) was analyzed by the 16S ribosomal RNA gene clone library method. Chemical composition was also analyzed to compare with different kinds of narezushi. The chemical composition of the narezushi was similar to those obtained from samma-narezushi. Ninety-four clones were randomly selected and DNA sequences of cloned fragments (approx. 890 bp) were analyzed. The DNA sequences obtained were phylogenetically analyzed. The expected operational taxonomy units (OTUs) by Chao1 estimates and Shannon-Wiener index (H') at 97% identity threshold were 48 and 1.822, respectively. The sequence similarity of the cloned fragment was equal to or higher than 98% of the sequence of cultivated bacterial species in the public database. Most of the clones (85%) belonged to lactic acid bacteria (LAB). Lactobacillus curvatus was the most abundant species followed by Lactococcus piscium and Leuconostoc gasicomitatum, suggesting that these bacteria play important roles in the fermentation of saba-narezushi.