Genomic Diversity of Enterotoxigenic Strains of Bacteroides fragilis.
Genomic Diversity of Enterotoxigenic Strains of Bacteroides fragilis.
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DOI：
10.1371/journal.pone.0158171
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发表时间：
2016
期刊：
影响因子：
3.7
通讯作者：
Bernstein HD
中科院分区：
文献类型：
--
作者：
Pierce JV;Bernstein HD
脆弱拟杆菌的产肠毒素（ETBF）菌株是分泌一种名为脆弱溶素（Bft）的毒素的菌株子集。虽然已知ETBF菌株会引起结肠炎，并且最近与结直肠癌有关，但它们尚未得到很好的表征。通过对四株ETBF菌株的全基因组测序，我们发现这些菌株在基因组水平上表现出相当大的变异。只有少数主要位于BFT致病岛（BFT派）和侧翼CTn86接合转座子的基因是保守的，在所有四个菌株和第五个菌株的基因组先前测序。有趣的是，系统发育分析强烈表明BFT派在进化过程中多次被非转基因（NTBF）菌株获得。在表型水平上，我们发现ETBF菌株比NTBF菌株NCTC 9343更不适合，并且对它产生的生长抑制蛋白敏感。ETBF菌株还显示出比NTBF菌株更大的形成生物膜的趋势，这可能促进肿瘤形成。虽然ETBF菌株的基因组多样性提高了它们致病性不同的可能性，但我们的实验结果也表明它们具有由非通用遗传元件的不同组合所赋予的共同特性。
Enterotoxigenic (ETBF) strains of Bacteroides fragilis are the subset of strains that secrete a toxin called fragilysin (Bft). Although ETBF strains are known to cause diarrheal disease and have recently been associated with colorectal cancer, they have not been well characterized. By sequencing the complete genome of four ETBF strains, we found that these strains exhibit considerable variation at the genomic level. Only a small number of genes that are located primarily in the Bft pathogenicity island (BFT PAI) and the flanking CTn86 conjugative transposon are conserved in all four strains and a fifth strain whose genome was previously sequenced. Interestingly, phylogenetic analysis strongly suggests that the BFT PAI was acquired by non-toxigenic (NTBF) strains multiple times during the course of evolution. At the phenotypic level, we found that the ETBF strains were less fit than the NTBF strain NCTC 9343 and were susceptible to a growth-inhibitory protein that it produces. The ETBF strains also showed a greater tendency to form biofilms, which may promote tumor formation, than NTBF strains. Although the genomic diversity of ETBF strains raises the possibility that they vary in their pathogenicity, our experimental results also suggest that they share common properties that are conferred by different combinations of non-universal genetic elements.