Differential expression of the ToxR regulon in classical and El Tor biotypes of Vibrio cholerae is due to biotype-specific control over toxT expression
Differential expression of the ToxR regulon in classical and El Tor biotypes of Vibrio cholerae is due to biotype-specific control over toxT expression
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DOI：
10.1073/pnas.93.15.7991
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发表时间：
1996-07-23
影响因子：
11.1
通讯作者：
Bruss, PM
中科院分区：
文献类型：
--
作者：
DiRita, VJ;Neely, M;Bruss, PM
霍乱弧菌的两种主要致病生物型，经典型和埃尔托型，在其流行性方面表现出差异。它们在实验室中的行为也不同，因为El Tor菌株仅在非常严格的生长条件下产生两种主要毒力因子，霍乱毒素（CT）和毒素共调节菌毛（TCP），而经典菌株在标准实验室培养基中这样做。毒素和TCP的表达由两种激活蛋白ToxR和ToxT控制，它们以级联方式操作，其中ToxR控制ToxT的合成。两种生物型表达相等水平的ToxR，但只有经典菌株在标准培养基中生长时表达ToxT。在这份报告中，我们表明，CT和TCP的限制性表达，可以克服在El Tor株表达toxT独立的ToxR。缺乏功能性ToxT的El Tor菌株不表达CT或TCP，排除了在该生物型中存在用于毒力调节的隐蔽途径。这些结果可能对理解El Tor菌株相对于经典菌株的毒力降低的进化具有影响。
The two major disease-causing biotypes of Vibrio cholerae, classical and El Tor, exhibit differences in their epidemic nature. Their behavior in the laboratory also differs in that El Tor strains produce two major virulence factors, cholera toxin (CT) and the toxin coregulated pilus (TCP), only under very restricted growth conditions, whereas classical strains do so in standard laboratory medium. Expression of toxin and TCP is controlled by two activator proteins, ToxR and ToxT, that operate in cascade fashion with ToxR controlling the synthesis of ToxT. Both biotypes express equivalent levels of ToxR, but only classical strains appear to express ToxT when grown in standard medium. In this report we show that restrictive expression of CT and TCP can be overcome in El Tor strains by expressing toxT independently of ToxR. An El Tor strain lacking functional ToxT does not express CT or TCP, ruling out existence of a cryptic pathway for virulence regulation in this biotype. These results may have implications for understanding the evolution of El Tor strains toward reduced virulence with respect to classical strains.