AME 83:1-13 (2019)  -  DOI: https://doi.org/10.3354/ame01901

ABSTRACT: The bryozoan Bugula neritina hosts an uncultured gammaproteobacterial symbiont, ‘Candidatus Endobugula sertula’ (E. sertula), which also produces the defensive compounds known as bryostatins. These compounds are unpalatable and protect the larvae from predation. Recent studies have shown that the symbiont can be present or absent in B. neritina colonies. The factors determining the symbiotic state of the host are unknown and may include abiotic or biotic variables, including other members of the B. neritina microbiome, which are poorly studied. Here, we explored the relationships between host genotype, environmental factors, E. sertula frequency, and microbiome composition in 141 B. neritina colonies collected from the east coast of North America. We found that latitude, temperature, and host genotype did not correlate with symbiont frequency, but they did impact the overall microbiome composition of B. neritina. Furthermore, we found that symbiont frequency predicts the composition of the non-symbiont microbiome. We hypothesize that chemical or ecological interactions mediated by E. sertula determine the presence or absence of other microbial taxa, which are additionally impacted by environmental factors and host biology.

KEY WORDS: Symbiosis · Microbiome · Bryozoan · Chemical ecology