RESUMO
Background: Aeromonas hydrophila is a prevalent pathogenic bacterium in aquaculture that causes economic loss around the world. Antimicrobials are used to control and prevent the incidence of bacterial pathogens in aquaculture. However, they lead to the emergence of antimicrobial resistance strains and the accumulation of antibiotic residues in fish tissue. To address these issues, bacteriophages may be promising alternatives to many antibiotics in combating bacterial infections in aquaculture. Materials and Methods: The phage specific to A. hydrophila was isolated from domestic wastewater. The morphology of phages was analyzed using transmission electron microscopy. The genomic DNA of the Aeromonas phage T65 strain (APT65) phage was sequenced with a paired-end read length of 2 × 150 bp. The genome sequence was assembled and annotated. The tRNAs were predicted, and antimicrobial resistance and virulence genes were screened. A representation of the APT65 genome was constructed. Results: The genome of APT65 is linear double-stranded DNA with 85188 base pairs having 116 open reading frames (ORFs) and a G + C content of 39.41%. The 32 ORFs were predicted to encode proteins with known phage functions. No virulence factors, antibiotic resistance genes, or temperate lifestyle genes were found. The phage is icosahedral and measures 60 nm in diameter. Based on the whole genome sequence, APT65 belongs to Lahexavirus. Conclusions: The taxonomic analysis of the phage with a genome length of 85,188 bp revealed that it is a new species of the genus Lahexavirus. We announce the whole genome sequence of APT65, which should be named Lahexavirus APT65, as well as the absence of antimicrobial resistance and virulence factors from its genome. Based on our results, the Lahexavirus APT65 phage may have potential as a therapeutic agent to tackle antimicrobial resistance in aquaculture.
RESUMO
Turbot, Scophthalmus maximus, is a commercially important demersal flatfish species distributed throughout the Black Sea. Several studies performed locally with a limited number of specimens using both mitochondrial DNA (mtDNA) and microsatellite markers evidenced notable genetic variation among populations. However, comprehensive population genetic studies are required to help management of the species in the Black Sea. In the present study eight microsatellite loci were used to resolve the population structure of 414 turbot samples collected from 12 sites across the Black Sea. Moreover, two mtDNA genes, COI and Cyt-b, were used for taxonomic identification. Microsatellite markers of Smax-04 and B12-I GT14 were excluded from analysis due to scoring issues. Data analysis was performed with the remaining six loci. Loci were highly polymorphic (average of 17.8 alleles per locus), indicating high genetic variability. Locus 3/20CA17, with high null allele frequency (>30%), significantly deviated from HW equilibrium. Pairwise comparison of the FST index showed significant differences between most of the surveyed sampling sites (P < 0.01). Cluster analysis evidenced the presence of three genetic groups among sampling sites. Significant genetic differentiation between Northern (Sea of Azov and Crimea) and Southern (Turkish Black Sea Coast) Black Sea sampling sites were detected. The Mantel test supported an isolation by distance model of population structure. These findings are vital for long-term sustainable management of the species and development of conservation programs. Moreover, generated mtDNA sequences would be useful for the establishment of a database for S. maximus.
