Complete Genome Sequence of Streptococcus suis Serotype 14 Strain JS14

Abstract

Streptococcus suis is an important zoonotic agent leading to a variety of diseases in swine and can be transmitted to human beings upon close contact. Here, we report the complete genome sequence of S. suis serotype 14 strain JS14 which was isolated from a diseased pig in Jiangsu Province, China.

TEXT

Streptococcus suis infections have been considered a major problem worldwide in the swine industry (10, 21). Thirty-three serotypes of S. suis have been described (types 1 to 31, 33, and 1/2), and in addition to serotype 2, serotype 14 has also been associated with severe infections in pigs and humans (11, 16). However, almost all studies have been conducted with serotype 2 strains and little is known about serotype 14. Thus, a pathogenic serotype 14 strain, JS14, which was isolated from articulation of a diseased pig in Jiangsu Province, China, was chosen for sequencing.

The complete genome sequence of S. suis strain JS14 was determined by Solexa pyrosequencing (653,741,120 Mb of 75-bp paired-end reads with an insertion size of 500 bp) at Beijing Institute of Genomics. Assembly was performed using SOAPdenovo. Gaps were closed by primer walking and sequencing of PCR products. Coding sequences (CDSs) were predicted using Glimmer 3.02 (7) and GeneMarkS (2) and compared with a nonredundant protein database to obtain descriptions. tRNAs and rRNAs were identified using tRNAscan-SE (14) and RNAmmer (13), respectively.

The genome of strain JS14 consists of a single circular chromosome which is 2,137,435 bp in length, with a GC content of 41.22%. There are 2,106 CDSs that account for 88.4% of the genome, 62 tRNAs, 4 rRNA loci, and 26 IS elements. Seventeen putative genome islands (GIs) were identified in the genome, two of which harbored a tetracycline resistance gene and a macrolide efflux gene, respectively, and resulted in resistance to tetracycline, erythromycin, and azithromycin. In addition, one prophage region was found and was specific to S. suis JS14 compared to serotype 2 strains. Besides those phage-related genes, many other JS14-specific genes were found, and most of them were annotated as hypothetical proteins.

CPS has been considered to be essential for the virulence of the bacterium and to serve as an antigen to identify the serotype (5). Homologues of Cps2A, Cps2B, Cps2C, and Cps2D genes were also found in the cps locus of the JS14 genome, which indicated that these genes may play a common role in different serotypes (17). Overall, the cps locus in the JS14 genome showed strong similarity to that in serotype 1 strain identified earlier, which may explain why serotype-specific PCR method could not differentiate serotype 1 and serotype 14 (18). CDSs for a few virulence-associated factors, such as suilysin, extracellular protein factor, fibronectin/fibrinogen-binding protein (6), serum opacity-like factor (1), sortase A (15, 19, 20), peptidoglycan GlcNAc deacetylase (8), d-alanylated lipoteichoic acid (9), and subtilisin-like serine protease (3, 4, 12), which were confirmed to contribute to the virulence of serotype 2, were also found in the genome of JS14. Learning more about these factors would strengthen our understanding on the virulence of S. suis serotype 14. This determination of the complete genome sequence will promote the study of the pathogenesis of the infection and mechanisms of protection of S. suis serotype 14.

Nucleotide sequence accession number.

The complete genome sequence of S. suis serotype 14 has been assigned GenBank accession number CP002465.