Abstract
Streptococcus ruminantium sp. nov. of type strain GUT-187T, previously classified as Streptococcus suis serotype 33, is a recently described novel streptococcal species. This study was designed to determine the complete genome sequence of S. ruminantium GUT-187T using a combination of Oxford Nanopore and the Illumina platform, and to compare this sequence with the genomes of 27 S. suis representative strains. The genome of GUT-187T was 2,090,539 bp in size, with a GC content of 40.01%. This genome contained 1,961 predicted protein coding DNA sequences (CDSs); of these, 1,685 (85.9%) showed similarity with S. suis CDSs. Of the remaining 276 CDSs, 81 (29.3%) showed some degree of similarity with CDSs of other streptococcal species. The genome of GUT-187T contained no intact prophage. The numbers of prophages and CRISPR spacers, as well as the presence or absence of genes encoding CRISPR-associated proteins, differed in S. ruminantium and S. suis. A phylogenetic analysis indicates that GUT-187T may be outgroup to the S. suis strains in our sample, thereby justifying its classification as distinct species. Gene mapping indicated 10.2 times of massive genome rearrangements in average occurred between S. ruminantium and S. suis. There was no significant statistical difference in clusters of orthologous group distribution between S. ruminantium and S. suis.