Comparison between the gut bacterial community of laboratory cultured and wild Daphnia

The fitness of an organism is often impacted by the composition and biological activity of its associated microbial community (i.e., the microbiota). Many factors, including host genetics, diet, temperature and chemicals, can influence the microbial community composition. Furthermore, these factors can differ strongly between natural and laboratory environments. Consequently, several studies have highlighted results from laboratory experiments investigating host-associated microbiota to be conflicting with those obtained under field conditions. Here, we compared the Daphnia magna gut bacterial communities in natural host populations with those of laboratory cultured hosts. We further analyzed changes in the gut microbiota after transferring hosts from natural populations to the laboratory on the short- and long-term. Results show that, in general, the gut microbiota from natural populations differ from those of laboratory cultures and that their composition and diversity changed one hour after being transferred to the laboratory. However, over the following 14 days the composition and diversity remained relatively stable. On the longer term, however, namely after two years of rearing hosts in the laboratory, the composition and diversity of the gut microbiota was strongly altered compared to the initial state. Our findings indicate that the gut microbiota of Daphnia magna in laboratory experiments is only partly representative for natural field conditions, and that caution should be taken when interpreting results from laboratory experiments for natural settings.