ena-STUDY-STATION BIOLOGIQUE DE ROSCOFF-17-03-2014-09:29:15:656-504
Role of V. splendidus related strains in an oyster mortality outbreak.
In May 2011, specific pathogen free (SPF) oysters were transferred to open seawater for 2 weeks and then reintroduced in a controlled environment to reveal the disease. Mortalities started at day 3 and reached a maximum of 50% at day 5.  Each day, Vibrionaceae strains infecting living oysters were isolated on selective media. The isolates were characterized by partial sequencing of a protein coding gene (gyrB)  and virulence was investigated by oyster experimental infection.  The superimposition of gyrB phylogeny with virulence phenotype led to the identification of a population,  containing V. crassostreae type strain , and only virulent strains. To further explore the genomic diversity of strains belonging to this population 16 virulent isolates (11 from the present study and 5 from a 2001 mortality outbreak including the LGP7T type strain) and 18 non-virulent isolates were sequenced by HTS (SOM). A phylogenetic analysis of concatenated nucleic acid sequences derived from 3229 shared proteins from the 34 genome sequences suggested the clonality of some isolates within our collection This was confirmed by an ANI value >99,5% and an accessory genome <150 CDS between isolates (data not shown). Consequently only 21/34 isolate were considered as distinct strains.
In May 2011, specific pathogen free (SPF) oysters were transferred to open seawater for 2 weeks and then reintroduced in a controlled environment to reveal the disease. Mortalities started at day 3 and reached a maximum of 50% at day 5.  Each day, Vibrionaceae strains infecting living oysters were isolated on selective media. The isolates were characterized by partial sequencing of a protein coding gene (gyrB)  and virulence was investigated by oyster experimental infection.  The superimposition of gyrB phylogeny with virulence phenotype led to the identification of a population,  containing V. crassostreae type strain , and only virulent strains. To further explore the genomic diversity of strains belonging to this population 16 virulent isolates (11 from the present study and 5 from a 2001 mortality outbreak including the LGP7T type strain) and 18 non-virulent isolates were sequenced by HTS (SOM). A phylogenetic analysis of concatenated nucleic acid sequences derived from 3229 shared proteins from the 34 genome sequences suggested the clonality of some isolates within our collection This was confirmed by an ANI value >99,5% and an accessory genome <150 CDS between isolates (data not shown). Consequently only 21/34 isolate were considered as distinct strains.