Flavobacterium tructae sp. nov. and Flavobacterium piscis sp. nov., isolated from farmed rainbow trout (Oncorhynchus mykiss) L. Zamora, 1 A. I. Vela, 1,2 C. Sa ´ nchez-Porro, 3 M. A. Palacios, 4 E. R. B. Moore, 5 L. Domı ´nguez, 1 A. Ventosa 3 and J. F. Ferna ´ ndez-Garayza ´ bal 1,2 Correspondence A. I. Vela avela@vet.ucm.es 1 Centro de Vigilancia Sanitaria Veterinaria (VISAVET), Universidad Complutense, 28040 Madrid, Spain 2 Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad Complutense, 28040 Madrid, Spain 3 Departamento de Microbiologı ´a y Parasitologı ´a, Facultad de Farmacia, Universidad de Sevilla, 41012 Sevilla, Spain 4 Piszolla, S.L., 37800 Alba de Tormes (Salamanca), Spain 5 Culture Collection University of Gothenburg (CCUG) and Department of Infectious Disease, Sahlgrenska Academy of the University of Gothenburg, 41346 Go ¨ teborg, Sweden Four Gram-staining-negative, catalase- and oxidase-positive, pale-orange pigmented bacterial strains (435-08 T , 47B-3-09, 412R-09 T and 60B-3-09) were isolated from diseased rainbow trout. Analysis of their 16S rRNA gene sequences suggested their adscription to the genus Flavobacterium. Strains formed two phylogenetic groups represented by strains 435-08 T and 47B-3-09 (group A), and strains 412R-09 T and 60B-3-09 (group B) displaying 16S rRNA sequence similarities greater than 99.8–99.9 % within their respective groups. Strain 435-08 T exhibited the highest levels of similarity with Flavobacterium aquidurense WB-1.1.56 T (98.6 % sequence similarity) and strain 412R-09 T with Flavobacterium frigidimaris KUC-1 T and Flavobacterium aquidurense WB-1.1.56 T (98.9 % and 98.6 % sequence similarity, respectively). DNA–DNA hybridization studies showed low levels of relatedness between strain 435-08 T and strain 412R-09 T and between both strains and the most closely related species of the genus Flavobacterium. The genomic DNA G+C contents of strains 435-08 T and 412R-09 T were 36.2 and 34.3 mol%, respectively. The predominant respiratory quinone of both strains was MK-6 and the major fatty acids were iso-C 15 : 0 ,C 16 : 1 v7c and C 15 : 0 . The two groups of strains could be distinguished from each other and from related species of the genus Flavobacterium by a number of phenotypic properties. Phylogenetic, genotypic and phenotypic evidence indicated that strains of groups A and B represent two novel species of the genus Flavobacterium, for which the names Flavobacterium tructae sp. nov. (type strain 435-08 T 5CECT 7791 T 5CCUG 60100 T ) and Flavobacterium piscis sp. nov. (type strain 412R-09 T 5CECT 7911 T 5CCUG 60099 T ) are proposed. The genus Flavobacterium is a member of the family Flavobacteriaceae, phylum Bacteroidetes, and represents one of the genera with a rapidly increasing number of species. At the time of writing, the genus Flavobacterium comprised 90 described species with validly published names (Euze ´by, 1997; http://www.bacterio.net). Members of this genus have been isolated from a variety of environmental sources, including soil, water, sludge, plants, food products such as fish, meat, poultry, milk and lactic acid beverages, and human clinical specimens (Bernardet & Nakagawa, 2006; Bernardet & Bowman, 2006). Several species of the genus Flavobacterium have been isolated from the fish farming environment, and some of them are (or potentially are) the aetiological agents of fish diseases, including Flavobacterium The GenBank/EMBL/DDBJ accession numbers for the 16S rRNA gene sequences of strains 435-08 T , 412R-09 T , 60B-3-09 and 47B-3-09 are HE612100, HE612101, HE774303 and HE774301, respectively. Two supplementary figures are available with the online version of this paper. International Journal of Systematic and Evolutionary Microbiology (2014), 64, 392–399 DOI 10.1099/ijs.0.056341-0 392 056341 G 2014 IUMS Printed in Great Britain