Optimal response to quorum-sensing signals varies in different host environments with different pathogen group size
Optimal response to quorum-sensing signals varies in different host environments with different pathogen group size
复制标题
在具有不同病原体群体大小的不同宿主环境中，对群体感应信号的最佳响应有所不同
DOI：
10.1101/775478
复制
发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Zhou L
中科院分区：
文献类型：
--
作者：
Zhou L
在基因表达的主要调节者中，如群体感应系统，遗传变异的持续存在是很难解释的。在这里，我们调查了两个替代假设的流行多态性群体感应在革兰氏阳性菌，即，使用不同的信号/受体对（"表型"）来调节相同的功能。首先，pherotypes或“兼性作弊”之间的社会互动可能有利于利用他人信号的罕见变体。第二，不同的表型可能会在不同的环境中增加适合度。我们评估了这些假设在无脊椎动物病原体苏云金芽孢杆菌，使用三个pherotypes表达在一个共同的遗传背景。在充分混合的宿主匀浆中可能发生兼性欺骗，条件是竞争的表型之间的串扰最小。然而，兼性作弊没有发生时，空间结构增加静态文化或自然的口腔感染，常见的pherotypes有较高的健身。有明确的支持环境依赖的健身; pherotypes不同的反应信号和平均竞争健身。值得注意的是，竞争健身随组的大小。与群体感应的典型社会进化模型相比，群体感应预测在较大的群体规模下对信号的响应更高，对信号响应最高的表型在较小的宿主中表现最好，其中感染具有较低的病原体群体规模。在这个系统中，低信号丰度似乎限制了宿主的适应性，而对信号的最佳响应水平在不同的宿主环境中有所不同。重要信息群体感应描述了微生物根据其局部种群大小改变基因调控的能力。一些成功的理论表明，这是一种合作形式，即只有在有足够的细菌生产相同产品的情况下，对共享产品的投资才是值得的。这一理论可以解释革兰氏阳性菌（如芽孢杆菌和葡萄球菌）中这些信号系统的遗传多样性。稀有基因型可能获得的优势（可以利用更常见的邻居的产品）可以解释为什么不同的基因型可以共存。我们表明，虽然这些社会相互作用可以发生在简单的实验室实验中，但它们不会发生在使用无脊椎动物病原体苏云金芽孢杆菌的自然感染中。相反，我们的研究结果表明，不同的基因型适应不同大小的主机。总的来说，社会模型不容易应用于这个系统，这意味着需要对这种形式的群体感应做出不同的解释。
The persistence of genetic variation in master regulators of gene expression, such as quorum-sensing systems, is hard to explain. Here, we investigated two alternative hypotheses for the prevalence of polymorphic quorum sensing in Gram-positive bacteria, i.e., the use of different signal/receptor pairs (‘pherotypes’) to regulate the same functions. First, social interactions between pherotypes or ‘facultative cheating’ may favor rare variants that exploit the signals of others. Second, different pherotypes may increase fitness in different environments. We evaluated these hypotheses in the invertebrate pathogen Bacillus thuringiensis, using three pherotypes expressed in a common genetic background. Facultative cheating could occur in well-mixed host homogenates provided there was minimal cross talk between competing pherotypes. However, facultative cheating did not occur when spatial structure was increased in static cultures or in naturalistic oral infections, where common pherotypes had higher fitness. There was clear support for environment-dependent fitness; pherotypes varied in responsiveness to signals and in mean competitive fitness. Notably, competitive fitness varied with group size. In contrast to typical social evolution models of quorum sensing which predict higher response to signal at larger group size, the pherotype with highest responsiveness to signals performed best in smaller hosts where infections have a lower pathogen group size. In this system, low signal abundance appears to limit fitness in hosts, while the optimal level of response to signals varies in different host environments.IMPORTANCEQuorum sensing describes the ability of microbes to alter gene regulation according to their local population size. Some successful theory suggests that this is a form of cooperation, namely, investment in shared products is only worthwhile if there are sufficient bacteria making the same product. This theory can explain the genetic diversity in these signaling systems in Gram-positive bacteria, such asBacillusandStaphylococcussp. The possible advantages gained by rare genotypes (which can exploit the products of their more common neighbors) could explain why different genotypes can coexist. We show that while these social interactions can occur in simple laboratory experiments, they do not occur in naturalistic infections using an invertebrate pathogen, Bacillus thuringiensis. Instead, our results suggest that different genotypes are adapted to differently sized hosts. Overall, social models are not easily applied to this system, implying that a different explanation for this form of quorum sensing is required.