Can the protein costs of bacterial resistance be offset by altered feeding behaviour?
Can the protein costs of bacterial resistance be offset by altered feeding behaviour?
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DOI：
10.1111/j.1365-2656.2008.01499.x
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发表时间：
2009-03-01
影响因子：
4.8
通讯作者：
Wilson, Kenneth
中科院分区：
文献类型：
--
作者：
Povey, Sonia;Cotter, Sheena C.;Wilson, Kenneth
在能量和营养方面，建立免疫反应可能是昂贵的，因此预计饮食摄入量应该随着感染而改变，以抵消这些成本。本研究的重点是一种专门的食草毛虫物种，非洲粘虫Spodoptera excepta，和一种机会主义细菌，枯草芽孢杆菌之间的相互作用。研究的主要目的是（i）建立昆虫宿主在系统性细菌感染中存活的大量营养素成本，（ii）确定膳食蛋白质和碳水化合物对免疫系统功能的相对重要性，以及（iii）确定宿主的正常进食行为是否会因细菌挑战而发生适应性变化，从而抵消抵抗感染的营养成本。我们表明，细菌感染幼虫的存活率随着膳食蛋白质与碳水化合物（P：C）比例的增加而增加，这表明蛋白质成本与细菌抗性相关。随着膳食蛋白质水平的增加，抗菌活性，酚氧化酶（PO）活性和血淋巴中的蛋白质水平增加，提供了一个潜在的来源，这种蛋白质成本。然而，也有证据表明，抗菌活性和酚氧化酶活性之间的生理权衡，作为幼虫的抗菌活性水平升高，在响应免疫激活减少PO activity.When之间的两种饮食中的选择不同的P：C的比例，幼虫注射亚致死剂量的细菌增加其蛋白质摄入量相对于控制幼虫，同时保持类似的碳水化合物摄入量水平。这些结果与S.受细菌感染后，无尾丝虫幼虫会改变其进食行为，从而可能提高可用于产生免疫系统成分和抵抗细菌感染所需的其他因子的蛋白质水平（“自我用药”）。
Mounting an immune response is likely to be costly in terms of energy and nutrients, and so it is predicted that dietary intake should change in response to infection to offset these costs. The present study focuses on the interactions between a specialist grass-feeding caterpillar species, the African armyworm Spodoptera exempta, and an opportunist bacterium, Bacillus subtilis.The main aims of the study were (i) to establish the macronutrient costs to the insect host of surviving a systemic bacterial infection, (ii) to determine the relative importance of dietary protein and carbohydrate to immune system functions, and (iii) to determine whether there is an adaptive change in the host's normal feeding behaviour in response to bacterial challenge, such that the nutritional costs of resisting infection are offset.We show that the survival of bacterially infected larvae increased with increasing dietary protein-to-carbohydrate (P:C) ratio, suggesting a protein cost associated with bacterial resistance. As dietary protein levels increased, there was an increase in antibacterial activity, phenoloxidase (PO) activity and protein levels in the haemolymph, providing a potential source for this protein cost. However, there was also evidence for a physiological trade-off between antibacterial activity and phenoloxidase activity, as larvae whose antibacterial activity levels were elevated in response to immune activation had reduced PO activity.When given a choice between two diets varying in their P:C ratios, larvae injected with a sub-lethal dose of bacteria increased their protein intake relative to control larvae whilst maintaining similar carbohydrate intake levels. These results are consistent with the notion that S. exempta larvae alter their feeding behaviour in response to bacterial infection in a manner that is likely to enhance the levels of protein available for producing the immune system components and other factors required to resist bacterial infections ('self-medication').