Cambridge University Press (copyright holder - Cambridge University Press)
Abstract
Kefir is a dairy product popular in many countries in Central Europe, especially in Poland and other
countries of Eastern and Northern Europe. This type of fermented milk is produced by a complex
population of symbiotic bacteria and yeasts. In this work, conditions for DNA extraction, involving
disruption of kefir grains and a cascade of cell lysis treatments, were established. Extraction procedure
of total microbial DNA was carried out directly from fresh kefir grains. Using different lysis stringency
conditions, five DNA pools were obtained. Genetic diversity of DNA pools were validated by RAPD
analysis, which showed differences in patterns of amplified DNA fragments, indicating diverse
microbial composition of all the analysed samples. These DNA pools were used for construction of
genomic DNA libraries for sequencing. As much as 50% of the analysed nucleotide sequences
showed homology to sequences from bacteria belonging to the Lactobacillus genus. Several
sequences were similar to sequences from bacteria representing Lactococcus, Oenococcus,
Pediococcus, Streptococcus and Leuconostoc species. Among homologues of yeast proteins were
those fromCandida albicans, Candida glabrata, Kluyveromyces lactis and Saccharomyces cerevisiae.
In addition, several sequences were found to be homologous to sequences from bacteriophages
