Author(s): Martinović Aleksandra, Radulović Zorica, Wind Anette, Janzen T, Obradović D
Keywords:LAB, pulsed gel field electrophoresis (PFGE), plasmid isolation, phage typing
The natural community of lactic acid bacteria isolated from farmhouse fermented milk products has been investigated. In such products, where no starters are added, fermentation occurs as a result of natural flora present in the surrounding environment. A total of 200 isolated strains were examined for their acidification activity and EPS formation. Out of the 200 isolated strains, 27 strains were selected for further investigation. They were further identified by 16S rRNA sequencing in order to obtain the identification at species level, which showed that 14 strains belong to Lactococcus lactis subsp. lactis, 10 of them to Lactobacillus sp and 3 strains belongs to Leuconostoc sp. To differentiate between strains the pulsed-field gel electrophoresis (PFGE) patterns, of 15 isolated lactococcal strains, was generated using SmaI or AscI. Unrelated strains yielded different patterns of digestion products. The plasmid isolation of these strains has also been conducted in order to compare these results to patterns of PFGE. Phage typing of the Lactococcus sp. strains has been conducted. All lactococcal strains were resistant against 41 phages (Chr. Hansen phage collection) representing the major phage groups known for Lactococcus. These results indicate that the strains represent a possible tool for cultures that have not been exposed to any industrial selection.
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