Complete genome sequence of Streptococcus agalactiae strain SA20-06, a fish pathogen associated to meningoencephalitis outbreaks

Abstract

Streptococcus agalactiae (Lancefield group B; GBS) is the causative agent of meningoencephalitis in fish, mastitis in cows, and neonatal sepsis in humans. Meningoencephalitis is a major health problem for tilapia farming and is responsible for high economic losses worldwide. Despite its importance, the genomic characteristics and the main molecular mechanisms involved in virulence of S. agalactiae isolated from fish are still poorly understood. Here, we present the genomic features of the 1,820,886 bp long complete genome sequence of S. agalactiae SA20-06 isolated from a meningoencephalitis outbreak in Nile tilapia (Oreochromis niloticus) from Brazil, and its annotation, consisting of 1,710 protein-coding genes (excluding pseudogenes), 7 rRNA operons, 79 tRNA genes and 62 pseudogenes.

Keywords: Streptococcus agalactiae; fish pathogen; genome sequencing.

Figure 1

Phylogenetic tree highlighting the position of S. agalactiae strain SA20-06 in relation to other selected strains of the species and others from the genus Streptococcus. The tree was based on 1,410 characters of the 16S rRNA gene sequence aligned using ClustalW2 [35]. The tree was inferred under the maximum likelihood criterion using MEGA5 software [36] and rooted with 16S rRNA sequence of fish pathogen Lactococcus garvieae (a member of the Streptococcaceae). The branches were mapped by the expected number of substitutions per site. The numbers above the branches are support values from 1,000 bootstrap replicates. The strains and their corresponding GenBank accession numbers (and, when applicable, draft sequence coordinates) for 16S rRNA genes are: S. agalactiae 18rs21, NZ_AAJO01000124; S. agalactiae ATCC13813, NR_040821; S. agalactiae 2603VR, NC_004116; S. agalactiae GB00112, AKXO01000029; S. agalactiae FSL_S3-026, AEXT01000002; S. agalactiae NEM316, AL766845; S. agalactiae SA20-06, NC_019048; S. agalactiae A909, NC_007432; S. agalactiae GD201008-001, CP003810; S. dysgalactiae subsp dysgalactiae ATCC 27957, CM001076; S. iniae 9117, NZ_AMOO01000003; S. parauberis KCT 11537, NC_015558; S. pyogenes alab49, NC_017596; S. pneumoniae ST556, NC_017769; S. thermophilus CNRZ1066, NC_006449; S. macedonicus ACA-DC 198, NC_016749; L. garvieae, AP009332.

Figure 2

Graphical circular map of the genome performed with CGview comparison tool [49]. From outer to inner circle: Genes on forward strand (color by COG categories), Genes on reverse strand (color by COG categories), RNA genes (tRNAs red, rRNAs green, other RNAs black), GC content, GC skew.