Feedback control architecture and the bacterial chemotaxis network.
Feedback control architecture and the bacterial chemotaxis network.
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DOI：
10.1371/journal.pcbi.1001130
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发表时间：
2011-05
影响因子：
4.3
通讯作者：
Papachristodoulou A
中科院分区：
文献类型：
--
作者：
Hamadeh A;Roberts MA;August E;McSharry PE;Maini PK;Armitage JP;Papachristodoulou A
细菌通过改变其游泳模式而向有利环境移动并远离有毒环境。这种反应受到趋化信号通路的调节，该通路有一个重要特征：它利用反馈来“重置”（适应）细菌的感知能力，从而使细菌能够感知一系列背景环境变化。这种反馈的作用已在大肠杆菌的简单趋化途径中得到了广泛研究。然而，最近发现大多数细菌具有多种大肠杆菌蛋白的趋化同源物，从而导致更复杂的途径。在本文中，我们研究了球形红杆菌中反馈的配置和作用，该细菌含有大肠杆菌中发现的趋化蛋白的多种同源物。多种蛋白质可以产生不同的可能的反馈配置，每种都具有不同的趋化性能质量以及对生物参数的变化和不确定性以及细胞内噪声的鲁棒性水平。我们开发了四种对应不同反馈配置的模型。通过一系列精心设计的实验，我们区分了这些模型并使其中三个模型无效。当检查这些模型对噪声和参数不确定性的鲁棒性时，我们发现未失效的模型优于其他模型。此外，它还具有“级联控制”反馈架构，广泛用于工程中以提高系统性能，包括鲁棒性。鉴于已知大多数细菌具有多种趋化途径，在本文中，我们表明某些反馈架构使它们比其他细菌具有更好的性能。特别是，级联控制可能是在更复杂的信号通路中实现稳健功能并提高其性能的重要特征。细菌通过改变游泳方式向有利的环境移动。这种反应（称为细菌趋化性）的一个重要特征是它们的感知能力保持独立于它们所处的背景环境。这一特征已在大肠杆菌中得到广泛研究，该细菌具有简单的趋化决定机制。然而，最近发现大多数细菌对于这种反应可能有一个更复杂的决策机制。在本文中，我们研究了一种此类细菌 R. sphaeroides 的趋化行为。我们开发了可能的决策机制的数学模型，并进行了实验程序来研究其有效性。我们发现，四种此类模型中只有一种可以解释 R. sphaeroides 的趋化反应。与其他模型相比，该模型对应于一种决策机制，该机制为细菌提供了优于其他细菌的游泳性能。此外，这种决策机制已被广泛用于提高多个工程系统的性能。我们认为这种机制可能在改善其他细菌和其他信号通路的趋化性能方面发挥重要作用。
Bacteria move towards favourable and away from toxic environments by changing their swimming pattern. This response is regulated by the chemotaxis signalling pathway, which has an important feature: it uses feedback to ‘reset’ (adapt) the bacterial sensing ability, which allows the bacteria to sense a range of background environmental changes. The role of this feedback has been studied extensively in the simple chemotaxis pathway of Escherichia coli. However it has been recently found that the majority of bacteria have multiple chemotaxis homologues of the E. coli proteins, resulting in more complex pathways. In this paper we investigate the configuration and role of feedback in Rhodobacter sphaeroides, a bacterium containing multiple homologues of the chemotaxis proteins found in E. coli. Multiple proteins could produce different possible feedback configurations, each having different chemotactic performance qualities and levels of robustness to variations and uncertainties in biological parameters and to intracellular noise. We develop four models corresponding to different feedback configurations. Using a series of carefully designed experiments we discriminate between these models and invalidate three of them. When these models are examined in terms of robustness to noise and parametric uncertainties, we find that the non-invalidated model is superior to the others. Moreover, it has a ‘cascade control’ feedback architecture which is used extensively in engineering to improve system performance, including robustness. Given that the majority of bacteria are known to have multiple chemotaxis pathways, in this paper we show that some feedback architectures allow them to have better performance than others. In particular, cascade control may be an important feature in achieving robust functionality in more complex signalling pathways and in improving their performance. Bacteria move towards favourable environments by changing their swimming pattern. An important feature of this response, which is called bacterial chemotaxis, is that their sensing ability remains independent of the background environment in which they find themselves. This feature has been studied extensively in the bacterium E. coli, which has a simple chemotaxis decision mechanism. However, it has been recently found that most bacteria could potentially have a much more complicated decision mechanism for this response. In this paper, we look at the chemotaxis behaviour of one such bacterium, R. sphaeroides. We develop mathematical models of possible decision mechanisms and undertake an experimental procedure to investigate their validity. We find that only one of four such models can explain the chemotaxis response in R. sphaeroides. Compared to the other models, this model corresponds to a decision mechanism that provides the bacterium with improved swimming performance over the others. Moreover, this decision mechanism has been used extensively to improve performance in several engineering systems. We suggest that this mechanism may play an important role in improving chemotactic performance in other bacteria and in other signalling pathways.
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