Introduction:
Many animals, including worms, carry communities of symbiotic microorganisms, known as the microbiome, that interact with their host's physiology, behavior, and ecology. These microorganisms provide various benefits to the host, such as aiding in nutrient acquisition, defense against pathogens, and adaptation to specific environments. While the importance of the microbiome in individual hosts has been widely studied, understanding how they jointly contribute to the host's overall success in different environments remains unexplored.
Experimental Approach:
To investigate how worm hosts and their associated microbiome jointly contribute to environmental adaptation, we conducted an experiment using the model organism Caenorhabditis elegans (C. elegans) and its bacterial symbiont Pseudomonas aeruginosa (P. aeruginosa). We established controlled environments that simulated two distinct habitats: one mimicking a pristine environment and the other resembling a polluted site.
Treatments and Experimental Design:
We set up four treatment groups:
1. Host-Pristine: C. elegans grown in the pristine environment without P. aeruginosa
2. Host-Polluted: C. elegans grown in the polluted environment without P. aeruginosa
3. Microbiome-Pristine: P. aeruginosa grown in the pristine environment without C. elegans
4. Microbiome-Polluted: P. aeruginosa grown in the polluted environment without C. elegans
Additionally, we had two interaction groups:
5. Co-Culture-Pristine: C. elegans and P. aeruginosa co-cultured in the pristine environment
6. Co-Culture-Polluted: C. elegans and P. aeruginosa co-cultured in the polluted environment
Data Collection and Analysis:
For each treatment and interaction group, we measured various fitness indicators, including growth rate, lifespan, fecundity, and stress tolerance. We also characterized the bacterial communities associated with the worms using DNA sequencing. Statistical analyses were performed to determine the effects of host-microbiome interactions, environmental conditions, and their interactions on the fitness outcomes.
Results:
Our findings revealed that the interplay between C. elegans hosts and P. aeruginosa microbiome significantly influenced their adaptation to different environments. When grown together in the pristine environment, the co-cultured worms exhibited higher fitness compared to either host or microbiome alone. This positive interaction was attributed to improved nutrient utilization and enhanced defense against specific stressors. However, in the polluted environment, the presence of P. aeruginosa had a detrimental effect on the host, leading to decreased fitness. Moreover, the microbiome composition itself was dynamic and varied depending on the environment and host presence.
Conclusion:
Our experimental demonstration underscores the profound role of host-microbiome interactions in determining environmental adaptation. C. elegans and P. aeruginosa jointly contribute to fitness outcomes depending on the environmental context. These findings contribute to a deeper understanding of the intricate relationships between hosts and their microbial symbionts in shaping ecological adaptations
