Complete Genome Sequence of Brucella abortus 134, a Biovar 1 Strain Isolated from Human

Abstract

Brucella abortus is one of the common pathogens causing brucellosis in China. Here, we report the genome sequence of B. abortus strain 134, a strain isolated from a human patient and belonging to biovar 1, the most highly represented biovar among B. abortus strains in China.

GENOME ANNOUNCEMENT

Brucellosis is one of the most common zoonotic infectious diseases worldwide, causing both great economic loss and public health burdens (6). Brucellosis is caused by bacteria of the genus Brucella and is characterized by abortion and infertility in many mammal species. Brucella is divided into different species according to pathogenicity, host preference, and phenotypic characteristics. These classical Brucella species display marked host ranges, for example, B. melitensis for sheep and goats, B. abortus for cattle, and B. canis for dogs (8). These bacteria constitute genetically committed groups evolutionarily linked to their preferred hosts (3). On the other hand, their hosts are not unique, which implies that each of these species has the capability to infect animal hosts other than its preferred species. Of the six conventional species, B. melitensis, B. abortus, B. suis, and B. canis can infect humans, with reported cases being of decreased virulence. Infection of a different host usually means that pathogenic bacteria have the capability to adapt to the host and results in genetic changes (7). Therefore, analysis of the genetic changes among strains from different hosts will provide information about bacterial adaptation mechanisms to hosts.

We are trying to decode genome sequences of strains from different Brucella species that were isolated from different hosts. Genome sequence comparisons of these isolates will be valuable for investigation of microevolution of Brucella. B. abortus is one of the common species isolated from northern China (2). B. abortus is divided into 8 biovars, of which biovar 1 is the most highly represented in China. Here, we report the genome sequence of B. abortus strain 134, a strain of biovar 1 isolated from a serum sample of a human patient. Genome sequence comparison of this strain to one isolated from the bacterium's natural host might provide information about its host adaptation and microevolution.

The genomic DNA of strain 134 was isolated from bacterial culture and sequenced with a HighSeq 2000 sequencer using the paired-end protocol. After filtering low-quality reads, the sequencing reads were assembled with Clcbio Genomics Workbench, version 5.5, by the de novo assembly method. A total of 141 contigs were generated, 71 of which were >10 kb and 121 of which were >1 kb. The average length of the contigs was 23 kb, and the total length was 3,248,564 bp. The final approximate coverage for these contigs was about 118×. After this, the genome sequence was annotated. Open reading frames (ORFs) were predicted by using RAST (1). rRNA was predicted by using RNAmmer (4), and tRNAs were identified with tRNAscan-SE 1.21 (5). The genome sequences were compared with those of the virulent B. abortus strain 9-941. Totals of 236 small deletions (56 in coding regions) and 3,218 polymorphism sites (1,876 in coding regions) were identified. Further comparative analysis between this strain and other Brucella strains will contribute to understanding their roles in host adaptation and bacterial microevolution.

Nucleotide sequence accession numbers.

The draft genome sequence of B. abortus strain 134 is available in GenBank under accession number AMPC00000000. The version described in this paper is the first version, AMPC01000000.