MacVittie, S. | Search bioRxiv

bioRxiv2025

Low-abundance taxa drive host microbiome response to temperature stress

Global climate change (GCC) will lead to the deterioration of host and microbiome health, posing a significant threat to complex symbioses. To gauge the reproducibility of thermal warming associated with GCC and the time scales on which it occurs, we monitored shifts in the Exaiptasia microbiome in 24 populations of the model cnidarian Exaiptasia diaphana over the course of six months. We identified a small cohort of temperature-sensitive amplicon sequence variants (ASVs) that reproducibly declined with increases in temperature before changes in host fitness occurred. After comparing these ASVs to global datasets, we found that the heat-impacted ASVs from our experiment were also present in many other cnidarian species, highlighting their potential as widespread indicators of thermal stress. Overall, we find that fewer than 1% of the microbiome within E. diaphana are heat indicator taxa, suggesting that a small but consistent group of ASVs signals the early stages of thermal stress.

ecology↗

bioRxiv2023

Microbiome depletion and recovery in the sea anemone, Exaiptasia diaphana, following antibiotic exposure

Microbial species that comprise host-associated microbiomes play an essential role in maintaining and mediating the health of plants and animals. While defining the role of individual or even complex communities is important towards quantifying the effect of the microbiome on host health, it is often challenging to develop causal studies that link microbial populations to changes in host fitness. Here, we investigated the impacts of reduced microbial load following antibiotic exposure on the fitness of the anemone, Exaiptasia diaphana and subsequent recovery of the hosts microbiome. Anemones were exposed to two different types of antibiotic solutions for three weeks and subsequently held in sterilized seawater for a subsequent three-week recovery period. Our results revealed that both antibiotic treatments reduced the overall microbial load during and up to one week post treatment. The observed reduction in microbial load was coupled to reduced anemone biomass, halted asexual reproduction rates, and for one of the antibiotic treatments, the partial removal of the anemones algal symbiont. Finally, our amplicon sequencing results of the 16S rRNA gene revealed that anemone bacterial composition only shifted in treated individuals during the recovery phase of the experiment, where we also observed a significant reduction in the overall diversity of the microbial community. Our work implies that the E. diaphanas microbiome contributes to host fitness and that the recovery of the of the hosts microbiome following disturbance with antibiotics leads to a reduced, but stable microbial state. ImportanceExaiptasia diaphana is an emerging model used to define the cellular and molecular mechanisms of coral-algal symbioses. E. diaphana also houses a diverse microbiome, consisting of hundreds of microbial partners with undefined function. Here, we applied antibiotics to quantify the impact of microbiome removal on host fitness as well as define trajectories in microbiome recovery following disturbance. We showed that reduction of the microbiome leads to negative impacts on host fitness, and that the microbiome does not recover to its original composition while held under aseptic conditions. Rather the microbiome becomes less diverse, but more consistent across individuals. Our work is important because it suggests that anemone microbiomes play a role in maintaining host fitness, that they are susceptible to disturbance events, and it is possible to generate gnotobiotic individuals that can be leveraged in microbiome manipulation studies to investigate the role of individual species on host health.

ecology↗