Genomic Characterization and Comparative Genomic Analysis of the Foodborne <i>Burkholderia gladioli</i> pv. <i>cocovenenans</i>

The <i>Burkholderia gladioli</i> pv. <i>cocovenenans</i> (<i>B. cocovenenans</i>) has been linked to fatal food poisoning cases, which could produce the deadly toxin of bongkrekic acid (BA). However, genomic characterization and toxin production pathways of <i>B. cocovenenans</i> strains remain elusive. This study aimed to explore the BA-producing ability associated with the evolution of the <i>bon</i> gene cluster and to analyze the intraspecies genomic diversity and phylogenetic relationships of <i>B. gladioli</i> based on the 17 genomes of <i>B. cocovenenans</i> strains isolated from Shenzhen City, China. Genome sequencing results suggested that the genome sizes of these <i>B. cocovenenans</i> strains were mostly approximately 8 Mb, with a GC content of approximately 68%. The evolutionary tree analysis of the whole-genome sequences showed that significant divergences and distinct cluster were exhibited among these <i>B. cocovenenans</i> strains. Comparative genomic analysis indicated that the genomes of strains 2020051, 2021031, and 2021067 contained the complete and entire <i>bon</i> gene cluster, supporting that these strains displayed obviously BA-producing ability. The genomes of strains 2021028 and 2020041 lacked the entire <i>bon</i> gene cluster. However, the genomes of strains 2021037, 2021024, 2021035, and 2021031 exhibited disruptions in their <i>bon</i> gene clusters. This finding indicated the loss of specific genes within the cluster, suggesting a reduced capability for BA production in these strains. The present results indicated that the <i>bon</i> gene cluster in the genome played a key role in the toxin BA biosynthesis of different <i>B. cocovenenans</i> strains. This study provided a comprehensive understanding of the relationship between genomic diversity and BA production of this lethal foodborne pathovar, which will potentially contribute to the risk identification and food poisoning outbreak prevention of <i>B. cocovenenans</i>.