Faculty of Information Technology and Bionics, Pázmány Péter Catholic University, Práter Street 50/A, Budapest, H-1085, Hungary.
Present address: RC Cancer Unit, Hutchison/MRC Research Centre, University of Cambridge, Hills Road, Cambridge, CB2 0XZ, UK.
Biol Direct. 2017 Sep 15;12(1):22. doi: 10.1186/s13062-017-0192-3.
Bacterial species present in multispecies microbial communities often react to the same chemical signal but at vastly different concentrations. The existence of different response thresholds with respect to the same signal molecule has been well documented in quorum sensing which is one of the best studied inter-cellular signalling mechanisms in bacteria. The biological significance of this phenomenon is still poorly understood, and cannot be easily studied in nature or in laboratory models. The aim of this study is to establish the role of differential signal response thresholds in stabilizing microbial communities.
We tested binary competition scenarios using an agent-based model in which competing bacteria had different response levels with respect to signals, cooperation factors or both, respectively. While in previous scenarios fitter species outcompete slower growing competitors, we found that stable equilibria could form if the fitter species responded to a higher chemical concentration level than the slower growing competitor. We also found that species secreting antibiotic could form a stable community with other competing species if antibiotic production started at higher response thresholds.
Microbial communities in nature rely on the stable coexistence of species that necessarily differ in their fitness. We found that differential response thresholds provide a simple and elegant way for keeping slower growing species within the community. High response thresholds can be considered as self-restraint of the fitter species that allows metabolically useful but slower growing species to remain within a community, and thereby the metabolic repertoire of the community will be maintained.
This article was reviewed by Michael Gromiha, Sebastian Maurer-Stroh, István Simon and L. Aravind.
在多物种微生物群落中存在的细菌物种经常对相同的化学信号做出反应，但浓度却大不相同。在群体感应中，已经充分记录了对于相同信号分子存在不同的响应阈值的现象，群体感应是细菌中研究得最好的细胞间信号机制之一。这种现象的生物学意义仍未得到很好的理解，并且在自然界或实验室模型中都不容易研究。本研究的目的是确定不同信号响应阈值在稳定微生物群落中的作用。
我们使用基于代理的模型测试了二元竞争场景，其中竞争细菌在信号、合作因子或两者方面分别具有不同的响应水平。虽然在以前的场景中，适应性更强的物种会淘汰生长较慢的竞争者，但我们发现，如果适应性更强的物种对更高的化学浓度水平做出反应，那么稳定的平衡就可以形成。我们还发现，如果抗生素的产生起始于更高的响应阈值，那么分泌抗生素的物种可以与其他竞争物种形成稳定的群落。
自然界中的微生物群落依赖于必然在适应性方面存在差异的物种的稳定共存。我们发现，不同的响应阈值为保持群落中生长较慢的物种提供了一种简单而优雅的方法。高响应阈值可以被视为适应性更强的物种的自我约束，这使得代谢有用但生长较慢的物种能够留在群落中，从而维持群落的代谢谱。
本文由 Michael Gromiha、Sebastian Maurer-Stroh、István Simon 和 L. Aravind 审稿。
