Identification of Flexibacter maritimus or Tenacibaculum maritimum from post-larvae of Litopenaeus vannamei ? Comment on Mouriño et al. (2008).

Recently, Mouriño et al. (2008) reported the first record in Brazil of the filamentous bacteria Flexibacter maritimus (Wakabayashi et al., 1986) from the hatching of Litopenaeus vannamei post-larvae (Boone, 1931). In our view, a generalized lack of clarity about this identification has occurred and the discussion of some issues raised in the work is beyond the scope of this commentary. As Mouriño et al. argued, the identification of this isolate as F. maritimus was influenced by the tests of Wakabayashi et al. (1986) and Chen et al. (1995), who had misclassified this microorganism within the Flexibacter genus. In fact, Suzuki et al. (2001), in a phylogenetic analysis and taxonomic study, demonstrated that Flexibacter maritimus is distantly related to Flexibacter flexilis, the type species of the genus Flexibacter. Therefore, Suzuki et al. (2001) concluded that this strain constitutes a new bacterial species in the genus Tenacibaculum, distinct from F. maritimus, named T. maritimum. Fourteen members are currently classified within this genus, including T. litopenaei isolated from shrimp in Taiwan (Sheu et al., 2007). Therefore, to avoid confusion with other bacteria, this note will use the name T. maritimum. Even though the bacterium reported by Mouriño et al. (2008) could be T. maritimum, one of the major constraints on the detection of this pathogen is the lack of methods to distinguish this microorganism from others that are phenotypically similar and phylogenetically related species, particularly those of the genus Flavobacterium and Cytophaga (Suzuki et al., 2001). The morphological, physiological and biochemical characteristics useful in the identification of Tenacibaculum maritimum have been detailed by several authors (see review Avendaño-Herrera et al., 2006a), and must contain at least a limited number of data (see Table 1). However, as Mouriño et al. show in their paper, only thirteen biochemical assays were done to propose T. maritimum as the cause of massive mortality of L. vannamei post-larvae. Some of these tests are not necessary for the identification of this pathogen as growth on