Biophysical Aspects of Resource Acquisition and Competition in Algal Mixotrophs
Biophysical Aspects of Resource Acquisition and Competition in Algal Mixotrophs
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DOI：
10.1086/660284
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发表时间：
2011-06
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影响因子：
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通讯作者：
B. Ward;S. Dutkiewicz;A. D. Barton;M. Follows
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作者：
B. Ward;S. Dutkiewicz;A. D. Barton;M. Follows
混合营养生物联合收割机结合了自养和异养营养，在淡水和海洋环境中都很丰富。最近的观察表明，混合营养体构成了很大一部分的生物量，噬菌性，和初级生产在贫营养环境。虽然混合营养在资源获取方面允许更大的灵活性，但任何优势都必须与代谢成本的相关增加相权衡，这似乎使混合营养体相对于专性自养生物和异养生物缺乏竞争力。使用一个理想化的细胞生理学和社区竞争模型，我们确定了一种机制，混合营养生物可以有效地胜过专家的营养元素。在低资源浓度下，当营养素的摄取受到向细胞扩散的限制时，可以最小化对细胞膜转运蛋白的投资。在这种情况下，混合营养生物可以获得有机和无机形式的限制元素，击败只能利用其中一种形式的专业竞争对手。这一优势足以抵消混合营养体所产生的额外代谢成本的两倍增加。这一机制对于维持高度贫营养的亚热带海洋的混合营养种群和生产力特别重要。
Mixotrophic organisms combine autotrophic and heterotrophic nutrition and are abundant in both freshwater and marine environments. Recent observations indicate that mixotrophs constitute a large fraction of the biomass, bacterivory, and primary production in oligotrophic environments. While mixotrophy allows greater flexibility in terms of resource acquisition, any advantage must be traded off against an associated increase in metabolic costs, which appear to make mixotrophs uncompetitive relative to obligate autotrophs and heterotrophs. Using an idealized model of cell physiology and community competition, we identify one mechanism by which mixotrophs can effectively outcompete specialists for nutrient elements. At low resource concentrations, when the uptake of nutrients is limited by diffusion toward the cell, the investment in cell membrane transporters can be minimized. In this situation, mixotrophs can acquire limiting elements in both organic and inorganic forms, outcompeting their specialist competitors that can utilize only one of these forms. This advantage can be enough to offset as much as a twofold increase in additional metabolic costs incurred by mixotrophs. This mechanism is particularly relevant for the maintenance of mixotrophic populations and productivity in the highly oligotrophic subtropical oceans.