Draft Genome Sequence of Brucella abortus Virulent Strain 544.

Here, we present the draft genome sequence and annotation of Brucella abortus virulent strain 544. The genome of this strain is 3,289,405 bp long, with 57.2% G+C content. A total of 3,259 protein-coding genes and 60 RNA genes were predicted.

GENOME ANNOUNCEMENT

Brucella spp. are Gram-negative facultative intracellular bacteria that cause a zoonosis called brucellosis (1). They are nonmotile and non-spore-forming coccobacilli belonging to the Alphaproteobacteria. Brucella spp. infect a wide range of animals, from dolphins and domestic animals to humans (2). The common bacterial virulence factors, such as exotoxins, pili, fimbriae, cytolysins, flagella, virulence plasmids, etc., are completely missing in Brucella species (3). Brucella abortus 544 is the most commonly used strain for experimental challenge in animals vaccinated with live or killed B. abortus vaccines (4). Here, we present the draft genome sequence of B. abortus 544 and its annotation.

The genomic DNA of B. abortus 544 was isolated using the DNeasy kit (Qiagen, Hilden, Germany). The 16S rRNA sequence of this strain showed 100% similarity with that of all other Brucella species. Therefore, species differentiation was performed by multilocus sequence analysis (MLSA) with 9 loci, as previously described (5). The genome was sequenced using the Ion Torrent personal genome machine (Life Technologies, Carlsbad, CA). In total, 2,736,169 reads, with an average read length of 217 bp, were obtained, which yielded 618.46 Mb of total sequenced bases with 187× fold coverage. The de novo assembly was performed using Mimicking Intelligent Read Assembly (MIRA) version 3.9.18 (6), which yielded 33 contigs. The largest contig was 329,558 bp long. The genome size of B. abortus strain 544 was 3,289,405 bp (3.28 Mb), with a G+C content of 57.2%. The genome sequence was annotated using the Rapid Annotations using Subsystems Technology (RAST) server (7) and the NCBI Prokaryotic Genome Annotation Process (http://www.ncbi.nlm.nih.gov/genome/annotation_prok/). A total of 3,319 genes were predicted. Of these predicted genes, 3,259 were protein-coding genes. Overall, 2,576 of the protein-coding genes were assigned putative functions, and 683 genes were annotated as hypothetical proteins. rRNA and tRNA genes were predicted using RNAmmer (8) and tRNAscan-SE 1.21 (9), respectively. A total of 60 RNA genes were predicted, of which 9 are rRNA genes and 51 are tRNA genes. B. abortus bv. 1 strain NI435a and B. abortus bv. 1 strain NI474 were identified as the closest neighbors of B. abortus 544 using RAST annotation.

Genes involved in virulence, disease, and the defense mechanisms of the bacterium were identified. These include genes responsible for antibiotic and toxic compound resistance, intracellular survival, invasion, among others. In-depth comparative analysis with other virulent strains and vaccine strains of B. abortus will help understand the pathogenic mechanism and intracellular life of Brucella organisms.

Nucleotide sequence accession numbers.

This whole-genome shotgun project has been deposited at DDBJ/EMBL/GenBank under the accession no. JPHK00000000. The version described in this paper is version JPHK01000000.