Serogroup conversion of Vibrio cholerae in aquatic reservoirs.
Serogroup conversion of Vibrio cholerae in aquatic reservoirs.
复制标题
DOI：
10.1371/journal.ppat.0030081
复制
发表时间：
2007-06
期刊：
影响因子：
6.7
通讯作者：
Schoolnik GK
中科院分区：
文献类型：
--
作者：
Blokesch M;Schoolnik GK
霍乱弧菌的环境水库是天然的水生栖息地，在那里它定植于桡足类蜕皮的几丁质外骨骼。霍乱弧菌在甲壳素表面的生长诱导了自然转化的能力，这是一种物种内基因交换的机制。霍乱弧菌不同的O-血清群决定因素是由一个遗传可变的生物合成基因簇编码的，该基因簇两侧是不同血清群之间保守的染色体区域。为了确定这一基因组基序和甲壳素诱导的自然转化是否能够使不同O群霍乱弧菌之间的血清群特异性基因簇交换，将一株霍乱弧菌O1 El Tor与一株O139孟加拉霍乱弧菌在同一几丁质表面浸泡在海水中的生物膜内共培养，获得了O1到O139转化子。通过比较基因组杂交、O抗原决定簇的生化和血清学特征以及O1到O139转化子对毒力O1特异性噬菌体的抵抗力，证实了O139供体对O1受体的血清群转换。血清组转换被证明是作为DNA大片段的一步交换发生的。交叉被定位于其他霍乱弧菌血清群共同的同源性区域，这些区域位于血清群特异性编码序列的两侧。这一结果和O37基因组DNA成功地将一株O1菌株转化为血清群表明，甲壳素诱导的自然转化可能是水生生境中血清群转化和霍乱弧菌变异株出现的常见机制，这些变异株更适合在环境利基中生存或对人类更具致病性。霍乱弧菌的蓄水池是水生环境，在那里它附着在小型甲壳类动物含有甲壳素的外壳上。甲壳素是霍乱弧菌的营养物质，它可以诱导霍乱弧菌的自然转化，通过这个过程，霍乱弧菌可以从同一栖息地的其他微生物那里获得新的基因。霍乱弧菌基因获取事件最引人注目的后果发生在1992年，当时印度和孟加拉国爆发了大规模霍乱疫情，并在亚洲蔓延。遗传分析表明，这次暴发是由于获得了一个基因簇，该基因簇将祖先的O1El Tor霍乱弧菌血清群转变为一个全新的血清群，命名为O139孟加拉。这份报告表明，O1 El Tor菌株获得O139基因簇可以通过自然转化介导，这可以发生在生活在甲壳素表面的细菌群落中。这次转化事件的O139衍生物没有被攻击O1菌株的噬菌体杀死，这在一定程度上解释了为什么在一些亚洲水源中，O139菌株取代了O1菌株。这些结果还说明了遗传和生态因素的组合如何导致环境水库中出现新的病原微生物。
The environmental reservoirs for Vibrio cholerae are natural aquatic habitats, where it colonizes the chitinous exoskeletons of copepod molts. Growth of V. cholerae on a chitin surface induces competence for natural transformation, a mechanism for intra-species gene exchange. The antigenically diverse O-serogroup determinants of V. cholerae are encoded by a genetically variable biosynthetic cluster of genes that is flanked on either side by chromosomal regions that are conserved between different serogroups. To determine whether this genomic motif and chitin-induced natural transformation might enable the exchange of serogroup-specific gene clusters between different O serogroups of V. cholerae, a strain of V. cholerae O1 El Tor was co-cultured with a strain of V. cholerae O139 Bengal within a biofilm on the same chitin surface immersed in seawater, and O1-to-O139 transformants were obtained. Serogroup conversion of the O1 recipient by the O139 donor was demonstrated by comparative genomic hybridization, biochemical and serological characterization of the O-antigenic determinant, and resistance of O1-to-O139 transformants to bacteriolysis by a virulent O1-specific phage. Serogroup conversion was shown to have occurred as a single-step exchange of large fragments of DNA. Crossovers were localized to regions of homology common to other V. cholerae serogroups that flank serogroup-specific encoding sequences. This result and the successful serogroup conversion of an O1 strain by O37 genomic DNA indicate that chitin-induced natural transformation might be a common mechanism for serogroup conversion in aquatic habitats and for the emergence of V. cholerae variants that are better adapted for survival in environmental niches or more pathogenic for humans. The reservoirs of Vibrio cholerae are aquatic environments, where it attaches to the chitin-containing shells of small crustaceans. Chitin serves as a nutrient for V. cholerae and it induces natural transformation, a process by which it acquires new genes from other microbes in the same habitat. The most compelling consequence of a V. cholerae gene acquisition event occurred in 1992 when a vast cholera epidemic erupted in India and Bangladesh and spread through Asia. Genetic analysis showed that this outbreak was due to the acquisition of a gene cluster that converted the ancestral V. cholerae O1 El Tor serogroup to an entirely new serogroup, designated O139 Bengal. This report shows that acquisition of the O139 gene cluster by an O1 El Tor strain can be mediated by natural transformation and that this can occur within a community of bacteria living on a chitin surface. The O139 derivatives of this transformation event were not killed by bacteriophages that attack O1 strains, explaining in part why O139 strains have replaced O1 strains in some Asian water sources. These results also illustrate how a combination of genetic and ecological factors can lead to the emergence of new pathogenic microbes in environmental reservoirs.
登录
查看更多内容
影响因子：
3.2
作者：
Beaber, JW;Hochhut, B;Waldor, MK
通讯作者：
Waldor, MK
影响因子：
11.4
作者：
BIK, EM;BUNSCHOTEN, AE;MOOI, FR
通讯作者：
MOOI, FR
影响因子：
3.6
作者：
Comstock, LE;Johnson, JA;Kaper, JB
通讯作者：
Kaper, JB
影响因子：
6.4
作者：
ALDOVA, E;LAZNICKOVA, K;LIETAVA, J
通讯作者：
LIETAVA, J
影响因子：
6.4
作者：
Faruque, SM;Saha, MN;Nair, GB
通讯作者：
Nair, GB