Characterization of a gene cluster for sialoglycoconjugate utilization in Bacteroides fragilis
Characterization of a gene cluster for sialoglycoconjugate utilization in Bacteroides fragilis
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DOI：
10.2152/jmi.59.79
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发表时间：
2012-02-01
影响因子：
0.7
通讯作者：
Kuwahara, Tomomi
中科院分区：
文献类型：
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作者：
Nakayama-Imaohji, Haruyuki;Ichimura, Minoru;Kuwahara, Tomomi
最近对脆弱拟杆菌全基因组序列的分析显示，在这种厌氧菌中多糖利用基因广泛重复。在这里，我们分析了一个独特的27 kb的基因簇（sgu）的13个唾液酸糖缀合物利用基因，其中包括唾液酸酶基因（nanH 1）在B。fragilis菌株YCH 46。这些基因组织紧密，多顺反子转录。比较PCR扫描表明，sgu位点是保守的拟杆菌菌株之间测试。基于通过逆转录酶PCR产生的转录谱，sgu基因座可以被分类为至少三个调节单元：1）唾液酸或唾液寡糖诱导的基因，2）可以通过分解代谢物阻遏下调的组成型表达的基因，和3）组成型表达的基因。在体外比较生长的sgu基因座缺失突变体（SGUM 172941）与野生型菌株表明，该基因座是必要的B。fragilis有效利用粘蛋白作为碳源。此外，SGUM 172941在竞争条件下对无菌小鼠肠道的定殖存在缺陷。这些数据表明，B. fragilis在宿主来源的唾液酸糖缀合物的利用和该厌氧菌在人肠道中的稳定定殖中起关键作用。
Recent analysis of the whole genome sequence of Bacteroides fragilis revealed extensive duplication of polysaccharide utilization genes in this anaerobe. Here we analyzed a unique 27-kb gene cluster (sgu) comprised of the 13 sialoglycoconjugates-utilization genes, which include the sialidase gene (nanH1) in B. fragilis strain YCH46. The genes were tightly organized and transcribed polycistronically. Comparative PCR scanning demonstrated that the sgu locus was conserved among the Bacteroides strains tested. Based on the transcriptional profiles generated by reverse transcriptase PCR, the sgu locus can be classified into at least three regulatory units : 1) sialic acid-or sialooligosaccharide- inducible genes, 2) constitutively expressed genes that can be down-regulated by catabolite repression, and 3) constitutively expressed genes. In vitro comparison of the growth of a sgu locus deletion mutant (SGUM172941) with a wild type strain indicates that this locus is necessary for B. fragilis to efficiently utilize mucin as a carbon source. Furthermore, SGUM172941 was defective in colonization of the intestines of germfree mice under competitive conditions. These data indicate that the sgu locus in B. fragilis plays a crucial role in the utilization of host-derived sialoglycoconjugates and the stable colonization of this anaerobe in the human gut.