Data from: Effects of host genetics and environment on egg-associated microbiotas in brown trout (Salmo trutta)

Recent studies found fish egg-specific bacterial communities that changed over the course of embryogenesis, suggesting an interaction between the developing host and its microbiota. Indeed, single-strain infections demonstrated that the virulence of opportunistic bacteria is influenced by environmental factors and host immune genes. However, the interplay between a fish embryo host and its microbiota has not been studied yet at the community level. To test whether host genetics affects the assemblage of egg-associated bacteria, adult brown trout (Salmo trutta) were sampled from a natural population. Their gametes were used for full-factorial in vitro fertilizations to separate sire from dam effects. In total, 2520 embryos were singly raised under experimental conditions that differently support microbial growth. High-throughput 16S rRNA amplicon sequencing was applied to characterize bacterial communities on milt and fertilized eggs across treatments. Dam and sire identity influenced embryo mortality, time until hatching and composition of egg-associated microbiotas, but no link between bacterial communities on milt and on fertilized eggs could be found. Elevated resources increased embryo mortality and modified bacterial communities with a shift in their putative functional potential. Resource availability did not significantly affect any parental effects on embryo performance. Sire identity affected bacterial diversity that turned out to be a significant predictor of hatching time: embryos associated with high bacterial diversity hatched later. We conclude that both host genetics and the availability of resources define diversity and composition of egg-associated bacterial communities that then affect the life history of their hosts.

已有研究发现，鱼类鱼卵特异性细菌群落会在胚胎发生（embryogenesis）过程中发生动态变化，这提示发育中的宿主与其微生物群（microbiota）之间存在相互作用。事实上，单菌株感染实验证实，条件致病菌（opportunistic bacteria）的毒力受环境因素与宿主免疫基因共同调控。然而，目前尚未在群落层面开展鱼类胚胎宿主与其微生物群之间相互作用的相关研究。为探究宿主遗传是否会影响鱼卵相关细菌的群落组装，研究人员从自然种群中采样获得成年褐鳟（Salmo trutta），利用其生殖细胞开展全因子（full-factorial）体外受精（in vitro fertilization）实验，以区分父本（sire）与母本（dam）的效应。总计2520枚胚胎被单独饲养于可差异化支持微生物生长的实验环境中，借助高通量16S rRNA扩增子测序（high-throughput 16S rRNA amplicon sequencing）技术，对不同处理组的精液（milt）与受精卵上的细菌群落进行表征分析。结果表明，母本与父本的遗传背景均会影响胚胎死亡率、孵化时长以及鱼卵相关微生物群的群落组成，但未发现精液与受精卵上的细菌群落之间存在关联。营养资源供给水平提升会增加胚胎死亡率，并改变细菌群落结构，同时伴随其推定功能潜能的变化；资源可获得性并未显著影响父本、母本效应对胚胎发育表现的作用。父本遗传背景会影响细菌群落多样性，而该多样性被证实是孵化时长的重要预测因子：细菌群落多样性较高的胚胎，其孵化时间更晚。综上，宿主遗传与资源可获得性共同决定了鱼卵相关细菌群落的多样性与组成，而这些群落特征反过来会影响宿主的生活史。