title: Sequencing of the tyrosine decarboxylase cluster of Lactococcus lactis IPLA 655 and the development of a PCR method for detecting tyrosine decarboxylating lactic acid bacteria.
abstract: The enzymatic decarboxylation of tyrosine produces tyramine, the most abundant biogenic amine in dairy products-especially in cheeses. The screening of lactic acid bacteria isolated from different artisanal cheeses and a number of microbial collections identified 22 tyramine-producing strains belonging to different genera. The Lactococcus lactis strain IPLA 655 was selected, and the genes encoding a putative tyrosyl tRNA synthetase, a tyrosine decarboxylase (tdcA), and a tyrosine-tyramine antiporter, found together as a cluster, were sequenced. The disruption of tdcA yielded a strain unable to produce tyramine. Comparison of the L. lactis IPLA 655 tdcA gene with database tdcA sequences led to the design of two primers for use in a PCR method that identified potential tyramine-producing strains. The proposed method can use purified DNA, isolated colonies, milk, curd, and even cheese as a template. Molecular tools for the rapid detection of tyramine-producing bacteria at any time during the fermentation process could help prevent tyramine accumulation in fermented foods. The proposed technique could be of great use to the food industry.
authors.affiliation: Instituto de Productos Lácteos de Asturias, Carretera de Infiesto s/n, 33300 Villaviciosa, Asturias, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Fernández
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Linares
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Alvarez
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001679:Biogenic Amines / Q000032:analysis / Q000096:biosynthesis; D002611:Cheese / Q000032:analysis / Q000382:microbiology*; D005285:Fermentation; D005516:Food Microbiology; D013294:Lactococcus lactis / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D005810:Multigene Family; D016133:Polymerase Chain Reaction / Q000379:methods; D016415:Sequence Alignment; D014439:Tyramine / Q000032:analysis* / Q000096:biosynthesis; D014445:Tyrosine Decarboxylase / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification*
chemical_list: D001679:Biogenic Amines; D014445:Tyrosine Decarboxylase; D014439:Tyramine