Microbial Diversity in Milled Rice as Revealed by Riosomal Intergenic Spacer Analysis

Abstract

Microbial diversity in milled rice was examined using culture-independent methods. Environmental DNA samples were extracted from commercial products of milled rice, and the intergenic spacer regions between the small and large subunit ribosomal RNA genes were amplified by ribosomal intergenic spacer analysis (RISA). The results indicated the presence of microbial communities in milled rice and subsequent sequencing of RISA amplicons has identified 17 unique microbial sequences. These include several sequences highly similar to known plant-associated microbes, including Pseudomonas fluorescens, Xanthomonas sacchari, and Pseudozyma antarctica, as well as to several uncultured bacteria. In addition, one sequence shows significant similarity to the sequence of Fusarium graminearum, a potent pathogenic fungus in foodstuffs that produces trichothecene mycotoxins. The potential presence of a pathogenic Fusarium fungus in milled rice was also suggested by a diagnostic PCR procedure that detects the genes involved in the production of trichothecene mycotoxins.