Sequencing of the full coding region of both genomic segments of seven betanodavirus strains isolated from different farmed species in Spain and Portugal revealed that six were reassortants, exhibiting a red-spotted grouper nervous necrosis virus (RGNNV)-type RNA1 and a striped jack nervous necrosis virus (SJNNV)-type RNA2. Analysis of sequences of reassortant strains at both the genomic and protein levels revealed the existence of differences compared with type strains of both genotypes. These differences were greater in the polymerase sequence, which is remarkable because viral structural proteins generally diverge more rapidly than non-structural proteins. Changes in two amino acids observed in the SJNNV capsid protein might be involved in the colonization of new host species by these reassortant strains. In addition, a more extensive phylogenetic analysis, including partial sequences of both RNA segments of 16 other Iberian nodaviruses, confirmed the existence of reassortment between RGNNV and SJNNV.

Characterization of Vibrio damsela strains isolated from turbot Scophthalmus maximus in Spain Belen ~o u z ' , Jens L. ~a r s e n~, Bent ~i e l s e n~, Juan L. ~arja', Alicia E. ~o r a n z o '

A survey of antibiotic-producing bacteria from the microbial flora attached to seaweeds and the study of their antibiotic capacities were carried out. From 5 species of green and brown marine algae, 224 bacterial strains were isolated and tested for antibiotic production. A total of 38 strains displayed antibiotic activity, withEnteromorpha intestinalis being the source of the highest number of producer strains. All epiphytic bacteria with antibiotic activity were assigned to thePseudomonas-Alteromonas group. Antagonism assays among the isolates demonstrated that each producer strain inhibits the growth of the other producers, as well as of some nonproducer strains also isolated from seaweeds. Likewise, an autoinhibitory effect was observed in all antibiotic-producing strains. Antibacterial spectra of all the strains include activity againstStaphylococcus, Alcaligenes, Pseudomonas, Vibrio, Pasteurella, andAchromobacter. A preliminary characterization of the antibiotic substances produced by these epiphytic bacteria demonstrated that they are low molecular weight compounds, thermolabile, and anionic and are not affected by proteolytic enzymes. The role that these inhibitory substances can play in the natural environment is discussed.

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We describe in this work a new iron uptake system encoded by chromosomal genes in pathogenic strains of Vibrio anguilarum. This iron uptake system differs from the plasmid-encoded anguibactin-mediated system present in certain strains of V. anguilarum in several properties. The siderophore anguibactin is not utilized as an external siderophore, and although characteristic outer membrane proteins are synthesized under iron-limiting conditions, these are not related to the plasinid-mediated outer membrane protein OM2 associated with ferric anguibactin transport. Furthermore, the siderophore produced by the plasmidless strains may be functionally related to enterobactin as demonstrated by bioassays with enterobactin-deficient mutants, although its behavior under various chemical treatments suggested major differences from that siderophore. Hybridization experiments suggested that the V. anguillarum chromosome-mediated iron uptake system is unrelated genetically to either the anguibactin or enterobactin-associated iron assimilation systems.One of the most important virulence factors in many pathogenic bacteria is the ability to utilize iron-from the host fluids by means of an efficient iron-sequestering system (5,8,18,22,34). Vibrio anguillarum is a bacterium highly pathogenic for different species of marine fish, causing the disease known as vibriosis (6,15,25). In strain 775, isolated from the Pacific Northwest coast of the United States, an iron uptake system is mediated by a 65-kilobase plasmid designated pJM1 (7,11,13). This system allows bacteria to grow at low concentrations of available iron imposed by the high-affinity iron-binding proteins present in the host fluids. Experimental infections demonstrated that possession of the pJM1 iron uptake genetic determinants is essential to cause disease (7,11,33,35).Genetic characterization of the pJM1-mediated iron uptake system allowed the location of the iron uptake genes to a 25-kilobase region of the pJM1 plasmid (12,29,33). These genes determine the synthesis of the two essential components involved in the iron uptake process: the diffusible siderophore anguibactin (1, 33) and a component of the receptor for the iron-siderophore complex identified as the 86-kilodalton outer membrane protein OM2 (2, 10). Other pathogenic strains of V. anguillarum isolated from cultured turbot on the northwestern Atlantic coast of Spain also harbor a plasmid which exhibits a high structural and functional homology with pJM1 (28). However, in recent studies with other virulent strains of V. anguillarum that were also iron uptake proficient, ho plasmids have been detected, suggesting that the iron uptake system of these strains must be chromosomally encoded (30).In the present work we report the characterization of this chromosome-mediated iron uptake system present in certain plasmidless strains of V. anguillarum. Our results indicate that this new system is different from the one encoded by the pJM1-like plasmids. * Corresponding author. MATERIALS AND METHODSBacterial strains. Th...