A toxin-antitoxin system promotes the maintenance of an integrative conjugative element.
A toxin-antitoxin system promotes the maintenance of an integrative conjugative element.
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DOI：
10.1371/journal.pgen.1000439
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发表时间：
2009-03
期刊：
影响因子：
4.5
通讯作者：
Waldor MK
中科院分区：
文献类型：
--
作者：
Wozniak RA;Waldor MK
SXT是一种整合和共轭元件（ICE），使许多临床分离的霍乱弧菌对多种抗生素产生耐药性。在大多数细胞中，这个~ 100 Kb的元件以位点特异性的方式整合到宿主基因组中；然而，sst可以切除形成染色体外环，这被认为是接合转移的底物。如果细胞分裂发生在元件重新整合之前，理论上可以产生缺乏SXT的子细胞。尽管约2%的携带sxt的细胞含有被切除的ICE形式，但没有检测到失去该元素的细胞。在这里，使用基于正选择的系统，很少检测到SXT损失，频率为1×10−7。正如预期的那样，切除对于损失是必要的，影响切除频率的因素改变了SXT损失的频率。我们筛选了整个100 kb的SXT基因组，并在SXT中鉴定出两个促进SXT稳定性的基因，现在命名为mosA和mosT（用于维持SXT抗毒素和毒素）。这两个基因，缺乏相似性的任何先前的特征基因，编码一个新的毒素-抗毒素对；mosT的表达严重损害了细胞生长，而mosA的表达改善了mosT的毒性。促进SXT切除的因子上调了mosAT的表达。因此，当该元件位于染色体外且易丢失时，SXT激活TA模块以最大限度地减少无SXT细胞的形成。整合和共轭元件（ICEs）是在许多细菌中发现的一组多样化的可移动遗传元件。这些元素整合到宿主染色体中，并切除并转移到其他细菌中。sst是一种编码对多种抗生素耐药的ICE，目前存在于大多数霍乱弧菌的临床分离株中。如果细胞分裂发生在其重新整合之前，切除SXT的细胞可能会失去ICE，但对促进ICE维持的机制的探索几乎没有受到关注。使用基于阳性选择的策略检测SXT丢失，我们发现这种ICE的丢失非常罕见（107个细胞中有1个）。两个基因，mosAT，与已知功能的基因缺乏相似性，被发现促进SXT维持。我们发现，在没有SXT的情况下，MosT可以阻断细胞生长，其活性可以被MosA中和。因此，这些基因编码了一个功能性的毒素-抗毒素（TA）系统。当SXT位于染色体外且易丢失时，mosAT表达增加，使无SXT细胞的形成最小化。mosAT的活性可能有助于维持细菌群体的抗生素耐药性。
SXT is an integrative and conjugative element (ICE) that confers resistance to multiple antibiotics upon many clinical isolates of Vibrio cholerae. In most cells, this ∼100 Kb element is integrated into the host genome in a site-specific fashion; however, SXT can excise to form an extrachromosomal circle that is thought to be the substrate for conjugative transfer. Daughter cells lacking SXT can theoretically arise if cell division occurs prior to the element's reintegration. Even though ∼2% of SXT-bearing cells contain the excised form of the ICE, cells that have lost the element have not been detected. Here, using a positive selection-based system, SXT loss was detected rarely at a frequency of ∼1×10−7. As expected, excision appears necessary for loss, and factors influencing the frequency of excision altered the frequency of SXT loss. We screened the entire 100 kb SXT genome and identified two genes within SXT, now designated mosA and mosT (for maintenance of SXT Antitoxin and Toxin), that promote SXT stability. These two genes, which lack similarity to any previously characterized genes, encode a novel toxin-antitoxin pair; expression of mosT greatly impaired cell growth and mosA expression ameliorated MosT toxicity. Factors that promote SXT excision upregulate mosAT expression. Thus, when the element is extrachromosomal and vulnerable to loss, SXT activates a TA module to minimize the formation of SXT-free cells. Integrative and conjugative elements (ICEs) are a diverse group of mobile genetic elements found in many bacteria. These elements integrate into the host chromosome as well as excise and transfer to other bacteria. SXT, an ICE that encodes resistances to multiple antibiotics, is currently present in most clinical isolates of V. cholerae, the cause of cholera. Cells in which SXT is excised can potentially lose the ICE if cell division occurs prior to its re-integration, but explorations of mechanisms that promote ICE maintenance have received almost no attention. Using a positive selection-based strategy to detect SXT loss, we found that loss of this ICE was very rare (1 in 107 cells). Two genes, mosAT, that lack similarity to genes of known function were found to promote SXT maintenance. We show that MosT blocks cell growth in the absence of SXT and its activity can be neutralized by MosA. Thus, these genes encode a functional toxin–antitoxin (TA) system. When SXT is extrachromosomal and vulnerable to loss, mosAT expression increases, minimizing the formation of SXT-free cells. The activity of mosAT may contribute to the maintenance of antibiotic resistance in bacterial populations.
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影响因子：
64.8
作者：
Beaber, JW;Hochhut, B;Waldor, MK
通讯作者：
Waldor, MK
细菌程序性细胞死亡和细菌多细胞行为。
影响因子：
4.5
作者：
通讯作者：
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影响因子：
3.2
作者：
Beaber, JW;Hochhut, B;Waldor, MK
通讯作者：
Waldor, MK
影响因子：
3.2
作者：
Böltner, D;MacMahon, C;Osborn, AM
通讯作者：
Osborn, AM
影响因子：
14.9
作者：
Lewis, JA;Hatfull, GF
通讯作者：
Hatfull, GF