GÖKKUŞAĞI ALABALIĞINDAN İZOLE EDİLEN LACTOCOCCUS PETAURİ KSUB4'ÜN TÜM GENOM SEKANS ANALİZİ ve GENOMİK KARAKTERİZASYONU

Lactococcosis is one of the significant bacterial infectious diseases observed in fish worldwide. Etiologically, this disease is primarily associated with Lactococcus garvieae and, more recently, the newly identified species L. petauri. Traditionally, L. garvieae has been recognized as the most important and best-characterized pathogen of this disease. However, recent studies have revealed that the role of L. petauri in the epidemiology of the disease is increasingly significant. In this study, an isolate (KSUB4) obtained from a trout farm in the Black Sea region in 2022 and confirmed as Lactococcus sp. by Polymerase Chain Reaction (PCR) was identified using Whole Genome Sequencing (WGS) analysis. The genome sequencing of the isolate was performed on the Illumina HiSeqX platform, and the raw sequence reads were assembled using the Unicycler v0.4.8 software after undergoing quality control processes. Annotation of the genome was carried out through the NCBI Prokaryotic Genome Automatic Annotation Pipeline (PGAP). Species-level identification of the isolate was performed using the Type Strain Genome Server (TYGS; https://tygs.dsmz.de/) platform. Virulence factors and antimicrobial resistance (AMR) genes were identified using the Virulence Factor Database (VFDB) and the Comprehensive Antibiotic Resistance Database (CARD), respectively. The analyses revealed that the genome of the KSUB4 isolate was 2,014,614 base pairs (bp) in length with a G+C content of 38.13%. Species identification analyses demonstrated that the KSUB4 isolate exhibited 51% digital DNA-DNA hybridization (dDDH) similarity with L. garvieae ATCC 49156T and 85.6% dDDH similarity with L. petauri 159469T. In the KSUB4 genome, 46 virulence genes with 35-71% similarity and 12 AMR genes with 53-95% similarity were detected. These findings shed light on the genetic potential of L. petauri in fish pathogenicity and provide significant insights into the antimicrobial resistance profile of this species.