title: Lactococcus lactis subsp. tructae subsp. nov. isolated from the intestinal mucus of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss).
abstract: The species Lactococcus lactis currently includes three subspecies; L. lactis subsp. lactis and L. lactis subsp. cremoris, isolated from milk sources, and L. lactis subsp. hordniae, isolated from the leafhopper Hordnia circellata. In this study, three strains, designated L105(T), I3 and L101, were isolated from the intestinal mucus of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss). These strains were closely related to members of the species Lactococcus lactis. Strain L105(T) showed 99.4 % 16S rRNA gene sequence similarity to that of the type strains L. lactis subsp. lactis NCDO 604(T) and L. lactis subsp. hordniae NCDO 2181(T) and showed 99.9 % similarity to the type strain Lactococcus lactis subsp. cremoris NCDO 607(T). Analysis of two housekeeping genes, rpoB and recA, confirmed the close relationship between the novel strains and L. lactis subsp. cremoris with similarities of 99.3 and 99.7 %, respectively. The three strains could, however, be differentiated from their closest relatives on the basis of several phenotypic characteristics, as was the case for L. lactis subsp. lactis and L. lactis subsp. hordniae, which were also closely related on the basis of 16S rRNA, rpoB and recA gene sequence similarities. The strains isolated in this study represent a new subspecies, for which the name Lactococcus lactis subsp. tructae subsp. nov. is proposed. The type strain is L105(T) ( = LMG 24662(T)  = DSM 21502(T)).
authors.affiliation: Laboratory of Fish Pathology, Faculty of Veterinary Sciences, Universidad de Zaragoza, 50013 Zaragoza, Spain.
authors.forename: Tania
authors.initials: T
authors.lastname: Pérez
authors.affiliation: Catalan Institute for Water Research (ICRA), Scientific and Technological Park of the University of Girona, 17003 Girona, Spain.
authors.forename: José Luis
authors.initials: JL
authors.lastname: Balcázar
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Salamanca - Consejo Superior de Investigaciones Científicas (IRNASA-CSIC), Salamanca, Spain.
authors.forename: Alvaro
authors.initials: A
authors.lastname: Peix
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Salamanca - Consejo Superior de Investigaciones Científicas (IRNASA-CSIC), Salamanca, Spain.
authors.forename: Angel
authors.initials: A
authors.lastname: Valverde
authors.affiliation: Departamento de Microbiología y Genética, Universidad de Salamanca, Salamanca, Spain.
authors.forename: Encarna
authors.initials: E
authors.lastname: Velázquez
authors.affiliation: Laboratory of Fish Pathology, Faculty of Veterinary Sciences, Universidad de Zaragoza, 50013 Zaragoza, Spain.
authors.forename: Ignacio
authors.initials: I
authors.lastname: de Blas
authors.affiliation: Laboratory of Fish Pathology, Faculty of Veterinary Sciences, Universidad de Zaragoza, 50013 Zaragoza, Spain.
authors.forename: Imanol
authors.initials: I
authors.lastname: Ruiz-Zarzuela
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics; D007422:Intestines / Q000382:microbiology*; D013294:Lactococcus lactis / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008969:Molecular Sequence Data; D009093:Mucus / Q000382:microbiology*; D017686:Oncorhynchus mykiss / Q000382:microbiology; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012487:Salmonidae / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S