Discrepancies between the phenotypic and genotypic characterization of Lactococcus lactis cheese isolates

• Published in: Letters in applied microbiology Vol. 43; no. 6; pp. 637 - 644
• Main Authors: Plaza, M. de la, Rodríguez, A, Fernández de Palencia, P, Martínez-Cuesta, M.C, Peláez, C, Requena, T
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.12.2006; Blackwell Publishing Ltd; Blackwell Science
• Subjects: amino acid catabolism; Amino Acid Sequence; Biological and medical sciences; Cheese - microbiology; DNA, Bacterial - analysis; Food Handling; Food Microbiology; Fundamental and applied biological sciences. Psychology; Genetic Variation; Genotype; Lactococcus lactis; Lactococcus lactis - classification; Lactococcus lactis - genetics; Lactococcus lactis - growth & development; Lactococcus lactis - isolation & purification; Microbiology; Molecular Sequence Data; Phenotype; Phylogeny; plasmid; Random Amplified Polymorphic DNA Technique - methods; RAPD; Sequence Homology, Amino Acid; wild strains; Lactococcus lactis; Lactic acid bacteria; Applied microbiology; RAPD; amino acid catabolism; Genotype; Cheese; Random amplified polymorphic DNA marker; Characterization; Plasmid; Streptococcaceae; Phenotype; Aminoacid; wild strains; Bacteria; Micrococcales; Isolate; Catabolism
• ISSN: 0266-8254; 1472-765X
• DOI: 10.1111/j.1472-765X.2006.02012.x

The use of randomly amplified polymorphic DNA (RAPD)-PCR fingerprinting and plasmid profiles to determine at the strain level, the similarity of Lactococcus lactis isolates obtained during sampling of traditional cheeses and to verify its correspondence to the selected phenotypic characteristics. A total of 45 L. lactis isolates were genotypically analysed by RAPD-PCR fingerprinting and plasmid patterns. Phenotypic traits used to compare strains were proteolytic, acidifying, aminotransferase (aromatic and branched chain aminotransferase) and α-ketoisovalerate decarboxylase (Kivd) activities. The results show that 23 isolates could be grouped in clusters that exhibited 100% identity in both their RAPD and plasmid patterns, indicating the probable isolation of dominant strains during the cheese sampling process. However, there were phenotypic differences between isolates within the same cluster that included the loss of relevant technological properties such as proteinase activity and acidifying capacity or high variation in their amino acid converting enzyme activities. Likewise, the analysis of a specific attribute, Kivd activity, indicated that 7 of 15 isolates showed no detectable activity despite the presence of the encoding (kivd) gene. Phenotypic differences found between genotypically similar strains of L. lactis strains could be linked to differences in enzymatic expression. Phenotypic analysis of L. lactis isolates should be considered when selecting strains with new cheese flavour forming capabilities.