Jiangsu Key Laboratory for Biodiversity and Biotechnology, School of Biological Sciences, Nanjing Normal University, 1 Wenyuan Road, Nanjing, 210023, China.
Microb Ecol. 2022 Oct;84(3):911-921. doi: 10.1007/s00248-021-01900-x. Epub 2021 Oct 29.
Host genotype and environment are considered crucial factors in shaping Daphnia gut microbiome composition. Among the environmental factors, diet is an important factor that regulates Daphnia microbiome. Most of the studies only focused on the use of axenic diet and non-sterile medium to investigate their effects on Daphnia microbiome. However, in natural environment, Daphnia diets such as phytoplankton are associated with microbes and could affect Daphnia microbiome composition and fitness, but remain relatively poorly understood compared to that of axenic diet. To test this, we cultured two Daphnia magna genotypes (genotype-1 and genotype-2) in sterile medium and fed with axenic diet. To check the effects of algal diet-associated microbes versus free water-related microbes, Daphnia were respectively inoculated with three different inoculums: medium microbial inoculum, diet-associated microbial inoculum, and medium and diet-mixed microbial inoculum. Daphnia were cultured for 3 weeks and their gut microbiome and life history traits were recorded. Results showed that Daphnia inoculated with medium microbial inoculum were dominated by Comamonadaceae in both genotypes. In Daphnia inoculated with mixed inoculum, genotype-1 microbiome was highly changed, whereas genotype-2 microbiome was slightly altered. Daphnia inoculated with diet microbial inoculum has almost the same microbiome in both genotypes. The total number of neonates and body size were significantly reduced in Daphnia inoculated with diet microbial inoculum regardless of genotype compared to all other treatments. Overall, this study shows that the microbiome of Daphnia is flexible and varies with genotype and diet- and medium-associated microbes, but not every bacteria is beneficial to Daphnia, and only symbionts can increase Daphnia performance.
宿主基因型和环境被认为是塑造水蚤肠道微生物组组成的关键因素。在环境因素中，饮食是调节水蚤微生物组的重要因素。大多数研究仅关注使用无菌饮食和非无菌培养基来研究它们对水蚤微生物组的影响。然而，在自然环境中，水蚤的饮食（如浮游植物）与微生物相关，可能会影响水蚤微生物组的组成和适应性，但与无菌饮食相比，这方面的了解仍然相对较少。为了验证这一点，我们在无菌培养基中培养了两种大型水蚤基因型（基因型 1 和基因型 2），并用无菌饮食喂养它们。为了检查藻类饮食相关微生物与自由水相关微生物的影响，水蚤分别接种了三种不同的接种物：培养基微生物接种物、饮食相关微生物接种物以及培养基和饮食混合微生物接种物。水蚤培养了 3 周，并记录了它们的肠道微生物组和生活史特征。结果表明，在两种基因型中，接种培养基微生物接种物的水蚤主要由丛毛单胞菌科组成。在接种混合接种物的水蚤中，基因型 1 的微生物组发生了很大变化，而基因型 2 的微生物组则略有改变。接种饮食微生物接种物的水蚤在两种基因型中具有几乎相同的微生物组。与所有其他处理相比，无论基因型如何，接种饮食微生物接种物的水蚤的幼体总数和体型显著减少。总的来说，这项研究表明，水蚤的微生物组是灵活的，并且随基因型和饮食以及培养基相关微生物而变化，但并非所有细菌都对水蚤有益，只有共生菌才能提高水蚤的性能。
