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Deferred Growth Inhibition Assay to Quantify the Effect of Bacteria-derived Antimicrobials on Competition
Published on: September 3, 2016
Cross-inhibition among wild strains of Lactococcus lactis isolated from the same ecological niche
Juan A Centeno1, Pilar Gaya, Margarita Medina
1Departamento de Tecnologia de Alimentos, INIA, Madrid, Spain.
Abstract:
The cross-inhibition between 23 Lactococcus lactis subsp. lactis strains and 9 L. lactis subsp. cremoris strains with different randomly amplified polymorphic DNA patterns, all isolated from the same ecological niche--cheese made in the spring at a single factory from raw milk without added lactic starter cultures-was investigated. Cross-inhibition, as determined by the agar well diffusion assay, was recorded in 130 cases (12.7%) out of 1.024 total cases, with 109 cases due to supernatants of L. lactis subsp. lactis strains and 21 cases due to supernatants of L. lactis subsp. cremoris strains. L. lactis strains isolated in April, May, and June showed differences in their inhibitory activities, with cross-inhibition against each other in 34.7, 14.1, and 6.1% of the cases, respectively. Polymerase chain reaction techniques using specific primers for nisin, lacticin 481, and lactococcin A only revealed the presence of the structural gene of lacticin 481 in two L. lactis subsp. lactis strains.
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