Genome Sequence of the Pathogenic Intestinal Spirochete <em>Brachyspira hyodysenteriae</em> Reveals Adaptations to Its Lifestyle in the Porcine Large Intestine

Brachyspira hyodysenteriae is an anaerobic intestinal spirochete that colonizes the large intestine of pigs and causes swine dysentery, a disease of significant economic importance. The genome sequence of B. hyodysenteriae strain WA1 was determined, making it the first representative of the genus Brachyspira to be sequenced, and the seventeenth spirochete genome to be reported. The genome consisted of a circular 3,000,694 base pair (bp) chromosome, and a 35,940 bp circular plasmid that has not previously been described. The spirochete had 2,122 protein-coding sequences. Of the predicted proteins, more had similarities to proteins of the enteric Escherichia coli and Clostridium species than they did to proteins of other spirochetes. Many of these genes were associated with transport and metabolism, and they may have been gradually acquired through horizontal gene transfer in the environment of the large intestine. A reconstruction of central metabolic pathways identified a complete set of coding sequences for glycolysis, gluconeogenesis, a non-oxidative pentose phosphate pathway, nucleotide metabolism, lipooligosaccharide biosynthesis, and a respiratory electron transport chain. A notable finding was the presence on the plasmid of the genes involved in rhamnose biosynthesis. Potential virulence genes included those for 15 proteases and six hemolysins. Other adaptations to an enteric lifestyle included the presence of large numbers of genes associated with chemotaxis and motility. B. hyodysenteriae has diverged from other spirochetes in the process of accommodating to its habitat in the porcine large intestine.猪痢疾短螺旋体（Brachyspira hyodysenteriae）是一种厌氧性肠道螺旋体，可定殖于猪的大肠，并引发猪痢疾——一种具有显著经济重要性的家畜疫病。本研究完成了猪痢疾短螺旋体WA1菌株的全基因组测序，使其成为短螺旋体属（Brachyspira）首个完成全基因组测序的代表菌株，同时也是第17个被报道基因组序列的螺旋体。该基因组包含一条环状的3000694碱基对（bp）染色体，以及一条此前从未被报道过的35940 bp环状质粒。该螺旋体共编码2122个蛋白质编码序列。在预测得到的蛋白中，与肠道大肠杆菌（Escherichia coli）和梭菌属（Clostridium）物种的蛋白具有同源相似性的数量，多于与其他螺旋体蛋白的同源数量。其中诸多基因与物质转运及代谢相关，推测其可能通过大肠环境中的水平基因转移逐步获得。对中心代谢通路的重构分析显示，该菌拥有完整的糖酵解、糖异生、非氧化性磷酸戊糖途径、核苷酸代谢、脂寡糖生物合成以及呼吸电子传递链相关编码序列。一项值得关注的发现是，该质粒上携带有参与鼠李糖生物合成的基因。潜在毒力基因包括15种蛋白酶编码基因与6种溶血素编码基因。其对肠道寄生生活方式的适应性还体现为拥有大量与趋化性及运动性相关的基因。猪痢疾短螺旋体在适应猪大肠生境的演化过程中，已与其他螺旋体产生了遗传分化。