Rapid invasion by colicinogenic Escherichia coli with novel immunity functions.
Rapid invasion by colicinogenic Escherichia coli with novel immunity functions.
复制标题
具有新型免疫功能的产大肠杆菌的快速入侵。
DOI：
10.1099/13500872-142-8-2175
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Riley,MA
中科院分区：
文献类型：
--
作者：
Tan,Y;Riley,MA
细菌素被认为在细菌的侵袭动力学中发挥重要作用。最近，提出了“多样化选择”假说，该假说解决了一组细菌素（大肠杆菌素）的起源和多样化问题。根据这一假设，新的大肠杆菌素基因簇源自产生扩展免疫功能的突变。积极的选择有利于这些新的免疫力，然后迅速驱动携带进化的大肠菌素基因簇的菌株在当地群体中固定下来。为了测试这种由选择驱动的固定步骤，通过将新的产大肠杆菌素菌株引入已建立的产大肠杆菌素种群中来进行入侵实验。在所有情况下，表达新免疫功能的菌株的入侵都迅速发生，即使入侵者的初始频率相当低。这些入侵主要归因于大肠杆菌素的杀伤作用。其他因素，如生长速度、大肠菌素产生水平和稳定期存活率，在入侵过程中发挥的作用非常小。这些结果为作用于大肠菌素基因簇的多样化选择的假设提供了直接证据，并阐明了大肠菌素的生态作用。
Bacteriocins have been suggested to play an important role in the invasion dynamics of bacteria. Recently, the ‘diversifying selection’ hypothesis has been proposed, which addresses the origin and diversification of one group of bacteriocins, the colicins ofEscherichia coli. According to this hypothesis, novel colicin gene clusters arise from mutations generating expanded immunity functions. Positive selection, favouring these novel immunities, then rapidly drives strains carrying the evolved colicin gene clusters to fixation in the local population. To test this fixation step driven by selection, invasion experiments were carried out by introducing novel colicinogenic strains into established colicinogenic populations. In all cases, invasion by strains expressing novel immunity functions occurred rapidly, even when initial frequencies of the invader were quite low. These invasions were attributed primarily to colicin killing effect. Other factors, such as growth rate, level of colicin production and stationary-phase survival rate, were shown to play very minor roles in the invasion process. These results provide direct evidence for the hypothesis of diversifying selection acting on colicin gene clusters and shed light on the ecological role of colicins.