Tenacibaculosis, a bacterial disease mainly caused  by  Tenacibaculummaritimum is one of the most devas- tating infectious diseases of farmed marine finfish world- wide (Avendaño-Herrera  et al ., 2006a). T. maritimum has been described as the causative agent of gliding  bacterial disease (or tenacibaculosis) in a great variety  of valuable marine fish species such as turbot  Scophthalmusmaximus , salmon  Salmosalarand  Oncorhynchus kisutch , Senegalese sole Solea senegalensis,Dover sole  Solea solea , gilthead  seabream  Sparus aurata , red seabream  Pagrus major, black seabream  Acanthopagrusschlegelii, sea bass  Dicentrarchus labrax and flounder  Paralichthys olivaceus (McVicar and White, 1979; Wakabayashi  et al ., 1984; Devesa  et al ., 1989; Bernardet  et al ., 1990; Chen  et al ., 1995; Ostland  et al ., 1999; Santos  et al .,  1999; Bader and Starliper, 2002; Avendaño-Herrera  et al ., 2004). In the last decade, the genus  Tenacibaculum has grown rapidly with the description of several new  members, being currently formed by 15 species. One  of them is  Tenacibaculum soleaewhich has been  reported to be pathogenic for Senegalese sole,  turbot, wedge sole  Dicologoglossacuneataand brill  Scophthalmusrhombus(Piñeiro-Vidal  et al ., 2008;  López  et al ., 2010). To our knowledge, only two  reports are available at present for studying  T. soleae :  the first description of the species (Piñeiro-Vidal  et al .,  2008) and a study in which serological and molecular  characterization of isolates from flatfish was performed  (López  et al ., 2010). Therefore, the number of cur- rently available isolates of  T. soleaefor these studies is  very small, and limited only to strains isolated from  flatfish. For the better understanding of this species,  the isolation and characterization of new isolates from  other sources would be a great contribution to deter- mine their possible intraspecific diversity, from a pheno- typic, serological and molecular point of view. Sea bass culture, along with the sea bream, repre- sents the largest marine fish farming in Europe. Pas- teurellosis ( Photobacterium damselaesubsp . piscicida infection), vibriosis ( Vibrioanguillarum infection) and  tenacibaculosis (i.e.  T. maritimum infection) are consid- ered until date the most important bacterial diseases of  this industry (Toranzo  et al ., 2005). However, as hap- pens with other fish cultures, once controlled these  pathologies by developing of prophylactic measures  and/or suitable vaccination programs, other new dis- eases may emerge. In fact, recently a novel bacterial  pathogen in sea bass cultures belonging to the genus  Tenacibaculum has been described, which has been  termed as  T. dicentrarchi (Piñeiro-Vidal  et al ., 2012). The present study is the first description of  T. soleae as the etiological agent of tenacibaculosis in cul- 魚病研究　FishPathology, 49(1), 16–22, 2014. 3 © 2014 The Japanese Society of Fish Pathology First IsolationandCharacterizationof Tenacibaculum soleae from SeaBass Dicentrarchus labrax Nuria Castro * , Sabela Balboa, Soledad Núñez, Alicia E. Toranzo and Beatriz Magariños Department of Microbiology andParasitology, Faculty of Biology-CIBUS&Institut of AquacultureUniversity of SantiagodeCompostela, SantiagodeCompostela, 15782, Spain (Received November 22, 2013) ABSTRACT —Tenacibaculum soleaeis a recently described pathogen that has been reported as the  causative agent of considerable losses in sole cultures in Spain. This report documents the first case of  T. soleae as an etiological agent of tenacibaculosis in farmed sea bass  Dicentrarchus labrax . Its identi- fication was performed employing phenotypical, serological and molecular methods. Although the sea  bass isolates were homogeneous from a biochemical, chemotaxonomic and molecular point of view, they  belonged to a serological group different from the type strain CECT7292, which can be of great impor- tance in the development of future vaccines and other methods of disease prevention in sea bass  industry. Virulence assays with a representative isolate confirmed the pathogenic potential for sea bass. The disease was experimentally reproduced by prolonged bath, while no mortalities could be recorded by  intraperitoneal injection. The results presented here show that  T. soleae must be taken into account as  an important pathogen in the marine aquaculture industry. Keywords: Tenacibaculumsoleae ,  Dicentrarchus labrax , fish pathogen, aquaculture, virulence * Corresponding author E-mail: nuria.castro@usc.es Research article