ABSTRACT

The Bacillus cereus group encompasses beneficial and harmful species in diverse niches and has a much debated taxonomy. Investigating whether selection has led to ecological divergence between phylogenetic clades can help understand the basis of speciation, and has implications for predicting biological safety across this group. Using three most terrestrial species in this group (B. cereus, Bacillus thuringiensis and Bacillus mycoides) we charactererized ecological specialization in terms of resource use, thermal adaptation and fitness in different environmental conditions and tested whether taxonomic species or phylogenetic clade best explained phenotypic variation. All isolates grew vigorously in protein rich media and insect cadavers, but exploitation of soil or plant derived nutrients was similarly weak for all. For B. thuringiensis and B. mycoides, clade and taxonomic species were important predictors of relative fitness in insect infections. Fully psychrotolerant isolates could outcompete B. thuringiensis in insects at low temperature, although psychrotolerance predicted growth in artificial media better than clade. In contrast to predictions, isolates in the Bacillus anthracis clade had sub-optimal growth at 37°C. The common ecological niche in these terrestrial B. cereus species is the ability to exploit protein rich resources such as cadavers. However, selection has led to different phylogenetic groups developing different strategies for accessing this resource. Thus, clades, as well as traditional taxonomic phenotypes, predict biologically important traits.

中文翻译：

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蜡状芽孢杆菌群陆地进化枝之间的环境适应差异

摘要

该蜡状芽孢杆菌组包括在不同的壁龛有益和有害物质，并有备受争议的分类。调查选择是否导致了进化进化枝之间的生态差异，可以帮助理解物种形成的基础，并且对预测这一群体的生物安全性具有重要意义。使用该组中三种最陆地物种（蜡状芽孢杆菌，苏云金芽孢杆菌和分枝杆菌））我们根据资源利用，热适应和在不同环境条件下的适应性来表征生态专业化，并测试分类物种或系统进化枝是否能最好地解释表型变异。所有分离株均在富含蛋白质的培养基和昆虫尸体中旺盛生长，但是对土壤或植物来源的养分的开发对所有人而言同样较弱。对于苏云金芽孢杆菌和蕈状芽孢杆菌，进化枝和分类学物种是昆虫感染中相对适应性的重要预测因子。在低温下，充分的抗精神病菌分离物可以在昆虫中与苏云金芽孢杆菌竞争，尽管抗精神病药物预测在人工培养基中的生长优于进化枝。与预测相反，炭疽芽孢杆菌进化枝在37°C下生长欠佳。这些陆生蜡状芽孢杆菌物种中常见的生态位是能够利用富含蛋白质的资源（例如尸体）。但是，选择导致不同的系统发育群体开发出不同的策略来访问该资源。因此，进化枝以及传统的分类表型预测生物学上重要的特征。