摘要

       长期的抗生素治疗如何影响宿主细菌之间的联系仍然是一个很大的未知数。蜜蜂肠道菌群的组成很简单，因此我们利用这个肠道菌群来研究长期抗生素治疗对宿主相关菌群的影响。我们研究了蜜蜂核心肠道菌群（Gilliamella apicola和Snodgrassella alvi）中两个丰富成员菌株的系统发育关系、基因组含量（GC百分比、基因组大小、基因数和CRISPR）和抗生素抗性基因（ARG）。家养蜜蜂受地理上不同的管理政策的影响，因此我们使用了两个研究蜂场，代表了蜂业中不同的抗生素治疗方案：低抗生素使用量（挪威）和高抗生素使用量（美国亚利桑那州）。我们应用全基因组鸟枪测序法对48g.心尖和22s.阿尔维进行了分析。我们在挪威和亚利桑那州的蜜蜂中发现了三个主要的根尖线虫亚群。对于根尖线虫，不同亚群之间的遗传含量存在显著差异，距离相似性计算表明亚群之间存在相似性差异。还发现了不同亚组之间的功能差异，如果胶降解酶（G.apicola）。此外，我们还利用Tet B决定簇的空间多态性，鉴定了转座子相关四环素抗性（tetb）的水平基因转移（HGT）。我们的研究结果支持蜜蜂肠道共生亚群可以通过HGT获得地理上不同的抗药性基因，从而抵抗长期的抗生素治疗并维持其功能。

        How long-term antibiotic treatment affects host bacterial associations is still largely unknown. The honeybee-gut microbiota has a simple composition, so we used this gut community to investigate how long-term antibiotic treatment affects host-associated microbiota. We investigated the phylogenetic relatedness, genomic content (GC percentage, genome size, number of genes and CRISPR) and antibiotic-resistant genes (ARG) for strains from two abundant members of the honeybee core gut microbiota (Gilliamella apicola and Snodgrassella alvi). Domesticated honeybees are subjected to geographically different management policies, so we used two research apiaries, representing different antibiotic treatment regimens in their apiculture: low antibiotic usage (Norway) and high antibiotic usage (Arizona, USA). We applied whole-genome shotgun sequencing on 48 G. apicola and 22 S. alvi. We identified three predominating subgroups of G. apicola in honeybees from both Norway and Arizona. For G. apicola, genetic content substantially varied between subgroups and distance similarity calculations showed similarity discrepancy between subgroups. Functional differences between subgroups, such as pectin-degrading enzymes (G. apicola), were also identified. In addition, we identified horizontal gene transfer (HGT) of transposon (Tn10)-associated tetracycline resistance (Tet B) across the G. apicola subgroups in the Arizonan honeybees, using interspace polymorphisms in the Tet B determinant. Our results support that honeybee-gut symbiont subgroups can resist long-term antibiotic treatment and maintain functionality through acquisition of geographically distinct antibiotic-resistant genes by HGT.

         https://onlinelibrary.wiley.com/doi/abs/10.1111/mec.14392