Abstract
The understanding of host-microbial partnerships has become a hot topic during the last decade as it has been shown that associated microbiota play critical roles in the host physiological functions and susceptibility to diseases. Moreover, the microbiome may contribute to host resilience to environmental stressors. The sea anemone Aiptasia is a good laboratory model system to study corals and their microbial symbiosis. In this regard, studying its bacterial microbiota provides a better understanding of cnidarian metaorganisms as a whole. Here, we investigated the bacterial communities of different Aiptasia host-symbiont combinations under long-term heat stress in laboratory conditions. Following a 16S rRNA gene sequencing approach we were able to detect significant differences in the bacterial composition and structure of Aiptasia reared at different temperatures. A higher number of taxa (i.e., species richness), and consequently increased α-diversity and β-dispersion, were observed in the microbiomes of heat-stressed individuals across all host strains and experimental batches. Our findings are in line with the recently proposed Anna Karenina principle (AKP) for animal microbiomes, which states that dysbiotic or stressed organisms have a more variable and unstable microbiome than healthy ones. Microbial interactions affect the fitness and survival of their hosts, thus exploring the AKP effect on animal microbiomes is important to understand host resilience. Our data contributes to the current knowledge of the Aiptasia holobiont and to the growing field of study of host-associated microbiomes.
Highlights
Corals and their association with different microbes, such as photosynthetic algae from the family Symbiodiniaceae (Lajeunesse et al, 2018) and diverse bacterial communities (Ritchie, 2006; Rosenberg et al, 2007; Ainsworth et al, 2014), is one of the most studied symbioses
We investigated the effect of long-term heat stress (>2 years) on the bacterial communities of four different Aiptasia host-symbiont combinations; H2, CC7, Red Sea (RS) and CC7-SSB01, an experimental combination resulting from reinfecting aposymbiotic CC7 with B. minutum originally from H2
Operational Taxonomic Units (OTUs) belonging to the family Rhodospirillaceae, Planctomycetaceae, and Cytophagaceae were significantly more abundant in heatstressed anemones compared to Aiptasia reared at 25◦C
Summary
Corals and their association with different microbes, such as photosynthetic algae from the family Symbiodiniaceae (Lajeunesse et al, 2018) and diverse bacterial communities (Ritchie, 2006; Rosenberg et al, 2007; Ainsworth et al, 2014), is one of the most studied symbioses. Coral responses to heat stress are not ubiquitous; some species can be severely affected (Carpenter et al, 2008; Hoogenboom et al, 2017; Scheufen et al, 2017) while others might be able to persist (Hoogenboom et al, 2017) It is still not fully known what drives resilience but evidence of shifts, or lack thereof, in the microbial composition of heatstressed corals strongly suggests that microbiota may be a crucial component of coral resilience (Bourne et al, 2008; Lee et al, 2015; Hadaidi et al, 2017)
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