Rumbaugh Kendra P, Diggle Stephen P, Watters Chase M, Ross-Gillespie Adin, Griffin Ashleigh S, West Stuart A
Department of Surgery, Texas Tech University Health Sciences Center, Lubbock, 79430, USA.
Curr Biol. 2009 Feb 24;19(4):341-5. doi: 10.1016/j.cub.2009.01.050.
The ability of pathogenic bacteria to exploit their hosts depends upon various virulence factors, released in response to the concentration of small autoinducer molecules that are also released by the bacteria [1-5]. In vitro experiments suggest that autoinducer molecules are signals used to coordinate cooperative behaviors and that this process of quorum sensing (QS) can be exploited by individual cells that avoid the cost of either producing or responding to signal [6, 7]. However, whether QS is an exploitable social trait in vivo, and the implications for the evolution of virulence [5, 8-10], remains untested. We show that in mixed infections of the bacterium Pseudomonas aeruginosa, containing quorum-sensing bacteria and mutants that do not respond to signal, virulence in an animal (mouse) model is reduced relative to that of an infection containing no mutants. We show that this is because mutants act as cheats, exploiting the cooperative production of signal and virulence factors by others, and hence increase in frequency. This supports the idea that the invasion of QS mutants in infections of humans [11-13] is due to their social fitness consequences [6, 7, 14] and predicts that increased strain diversity will select for lower virulence.
病原菌利用其宿主的能力取决于多种毒力因子，这些毒力因子是细菌响应自身释放的小分子自诱导物分子的浓度而释放的[1 - 5]。体外实验表明，自诱导物分子是用于协调合作行为的信号，并且这种群体感应（QS）过程可能被那些避免产生或响应信号成本的单个细胞利用[6, 7]。然而，群体感应在体内是否是一种可被利用的社会特性以及对毒力进化的影响[5, 8 - 10]，仍未得到验证。我们发现，在含有群体感应细菌和不响应信号的突变体的铜绿假单胞菌混合感染中，相对于不含突变体的感染，在动物（小鼠）模型中的毒力降低。我们表明，这是因为突变体充当了骗子，利用其他细菌合作产生的信号和毒力因子，因此其频率增加。这支持了这样一种观点，即群体感应突变体在人类感染中的入侵[11 - 13]是由于其社会适应性后果[6, 7, 14]，并预测菌株多样性的增加将选择更低的毒力。
