FSL J1-208, a Virulent Uncommon Phylogenetic Lineage IV Listeria monocytogenes Strain with a Small Chromosome Size and a Putative Virulence Plasmid Carrying Internalin-Like Genes

Abstract

ABSTRACTThe bacterial genusListeriacontains both saprotrophic and facultative pathogenic species. A small genome size has been suggested to be associated with the loss of pathogenic potential ofL. welshimeriandL. seeligeri. In this paper we present data on the genome ofL. monocytogenesstrain FSL J1-208, a representative of phylogenetic lineage IV. Although this strain was isolated from a clinical case in a caprine host and has no decreased invasiveness in human intestinal epithelial cells, our analyses show that this strain has one of the smallestListeriachromosomes reported to date (2.78 Mb). The chromosome contains 2,772 protein-coding genes, including well-characterized virulence-associated genes, such asinlA,inlB, andinlCand the fullprfAgene cluster. The small genome size is mainly caused by the absence of prophages in the genome ofL. monocytogenesFSL J1-208, and further analyses showed that the total size of prophage-related regions is highly correlated to chromosome size in the genusListeria. L. monocytogenesFSL J1-208 carries a unique type of plasmid of approximately 80 kbp that does not carry genes annotated as being involved in resistance to antibiotics or heavy metals. The accessory genes in this plasmid belong to the internalin family, a family of virulence-associated proteins, and therefore this is the first report of a potential virulence plasmid in the genusListeria.