Leach Whitney B, Carrier Tyler J, Reitzel Adam M
Department of Biological Sciences University of North Carolina at Charlotte Charlotte NC USA.
Ecol Evol. 2019 Aug 13;9(17):9935-9947. doi: 10.1002/ece3.5534. eCollection 2019 Sep.
Microbes can play an important role in the physiology of animals by providing essential nutrients, inducing immune pathways, and influencing the specific species that compose the microbiome through competitive or facilitatory interactions. The community of microbes associated with animals can be dynamic depending on the local environment, and factors that influence the composition of the microbiome are essential to our understanding of how microbes may influence the biology of their animal hosts. Regularly repeated changes in the environment, such as diel lighting, can result in two different organismal responses: a direct response to the presence and absence of exogenous light and endogenous rhythms resulting from a molecular circadian clock, both of which can influence the associated microbiota. Here, we report how diel lighting and a potential circadian clock impacts the diversity and relative abundance of bacteria in the model cnidarian using an amplicon-based sequencing approach. Comparisons of bacterial communities associated with anemones cultured in constant darkness and in light:dark conditions revealed that individuals entrained in the dark had a more diverse microbiota. Overall community composition showed little variation over a 24-hr period in either treatment; however, abundances of individual bacterial OTUs showed significant cycling in each treatment. A comparative analysis of genes involved in the innate immune system of cnidarians showed differential expression between lighting conditions in with significant up-regulation during long-term darkness for a subset of genes. Together, our studies support a hypothesis that the bacterial community associated with this species is relatively stable under diel light conditions when compared with static conditions and that particular bacterial members may have time-dependent abundance that coincides with the diel photoperiod in an otherwise stable community.
微生物可通过提供必需营养、诱导免疫途径以及通过竞争或促进相互作用影响构成微生物组的特定物种，在动物生理学中发挥重要作用。与动物相关的微生物群落可能会因当地环境而动态变化，而影响微生物组组成的因素对于我们理解微生物如何影响其动物宿主的生物学特性至关重要。环境中定期重复的变化，如昼夜光照，可导致两种不同的机体反应：对外源光的存在与否的直接反应以及由分子生物钟产生的内源性节律，这两者均可影响相关的微生物群。在此，我们报告昼夜光照和潜在的生物钟如何使用基于扩增子的测序方法影响模式刺胞动物中细菌的多样性和相对丰度。对在持续黑暗和光照：黑暗条件下培养的海葵相关细菌群落的比较表明，在黑暗中培养的个体具有更多样化的微生物群。在两种处理中，总体群落组成在24小时内变化不大；然而，每种处理中单个细菌操作分类单元（OTU）的丰度显示出显著的周期性变化。对刺胞动物先天免疫系统中涉及的基因进行的比较分析表明，光照条件之间存在差异表达，在长期黑暗中，一部分基因有显著上调。总之，我们的研究支持这样一种假设，即与该物种相关的细菌群落在昼夜光照条件下与静态条件相比相对稳定，并且在其他方面稳定的群落中，特定细菌成员可能具有与昼夜光周期一致的时间依赖性丰度。
