Assessment of the microbial diversity of Brazilian kefir grains by PCR-DGGE and pyrosequencing analysis.

The microbial diversity and community structure of three different kefir grains from different parts of Brazil were examined via the combination of two culture-independent methods: PCR-denaturing gradient gel electrophoresis (PCR-DGGE) and pyrosequencing. PCR-DGGE showed Lactobacillus kefiranofaciens and Lactobacillus kefiri to be the major bacterial populations in all three grains. The yeast community was dominated by Saccharomyces cerevisiae. Pyrosequencing produced a total of 14,314 partial 16S rDNA sequence reads from the three grains. Sequence analysis grouped the reads into three phyla, of which Firmicutes was dominant. Members of the genus Lactobacillus were the most abundant operational taxonomic units (OTUs) in all samples, accounting for up to 96% of the sequences. OTUs belonging to other lactic and acetic acid bacteria genera, such as Lactococcus, Leuconostoc, Streptococcus and Acetobacter, were also identified at low levels. Two of the grains showed identical DGGE profiles and a similar number of OTUs, while the third sample showed the highest diversity by both techniques. Pyrosequencing allowed the identification of bacteria that were present in small numbers and rarely associated with the microbial community of this complex ecosystem.