Microbiome structure of the fungid coral Ctenactis echinata aligns with environmental differences

Abstract

The significance of bacteria for eukaryotic functioning is increasingly recognized. Coral reef ecosystems critically rely on the relationship between coral hosts and their intracellular photosynthetic dinoflagellates, but the role of the associated bacteria remains largely theoretical. Here, we set out to relate coral‐associated bacterial communities of the fungid host species Ctenactis echinata to environmental settings (geographic location, substrate cover, summer/winter, nutrient and suspended matter concentrations) and coral host abundance. We show that bacterial diversity of C. echinata aligns with ecological differences between sites and that coral colonies sampled at the species’ preferred habitats are primarily structured by one bacterial taxon (genus Endozoicomonas) representing more than 60% of all bacteria. In contrast, host microbiomes from lower populated coral habitats are less structured and more diverse. Our study demonstrates that the content and structure of the coral microbiome aligns with environmental differences and denotes habitat adequacy. Availability of a range of coral host habitats might be important for the conservation of distinct microbiome structures and diversity.

Distinct Bacterial Microbiomes Associate with the Deep-Sea Coral Eguchipsammia fistula from the Red Sea and from Aquaria Settings

“…Indeed, here we found pronounced differences in the coral bacterial microbiome of in situ and ex situ E. fistula. Changes in the microbial community based on environmental differences were shown before by Roder et al (2015) where the microbiome of Ctenactis echinata was less structured and more diverse in lower populated coral habitats, indicating that preferred habitats align with more structured bacterial communities. A more extreme case of environmental adjustment was observed by Röthig et al (2016) where associated bacteria of Fungia granulosa changed under high salinity exposure over 29 days and suggested a shift toward increased osmolyte production, sulfur oxidation, and nitrogen fixation.…”

“…In particular, adjustment of associated bacteria to prevailing environmental conditions has been suggested to support acclimatization of the coral holobiont (Reshef et al, 2006). This notion is supported by recent studies that show, at least in part, flexible bacterial microbiomes of the coral holobiont to environmental change (Jessen et al, 2013;Roder et al, 2015;Hernandez-Agreda et al, 2016;Röthig et al, 2016;Ziegler et al, 2016Ziegler et al, , 2017. However, our knowledge on the role of the bacterial microbiome to coral holobiont function is still limited (Bourne and Webster, 2013;Bourne et al, 2016), although bacteria are shown to contribute to coral health (Rosenberg et al, 2007;Krediet et al, 2013) and are involved in nutrient cycling (Rädecker et al, 2015;Bourne et al, 2016).…”

“…Coral microbiomes are shown to vary to a degree across spatial, depth, and environmental distributions (Pantos et al, 2015;Roder et al, 2015;Hernandez-Agreda et al, 2016;Glasl et al, 2017). Rapid adjustment of the microbiome has also recently been reported under stressful environmental conditions and suggested to support holobiont functioning (Röthig et al, 2016;Ziegler et al, 2017).…”

“…More importantly, these microbiomes align functionally to the different environments (see below). As such, the notion of species-specific core microbiomes that are consistent over large geographical and environmental scales (Bayer et al, 2013a;Ainsworth et al, 2015;Roder et al, 2015;Hernandez-Agreda et al, 2016Ziegler et al, 2016;Neave et al, 2017) is in contrast to the highly variable core microbiome in E. fistula. Rather, it may suggest a limited association with obligate bacterial symbionts and/or a high flexibility in regard to bacterial symbionts.…”

Laboratory-Cultured Strains of the Sea Anemone Exaiptasia Reveal Distinct Bacterial Communities

“…studies (e.g., Littman et al, 2009;Pantos et al, 2015;Roder et al, 2015) have suggested that geographic location and environmental settings can determine the holobiont microbiome, whereas others (e.g., Hentschel et al, 2002;Fraune and Bosch, 2007;Montalvo and Hill, 2011;Lawler et al, 2016) have shown that bacterial communities are species-specific associations conserved over time and space. Moreover, coevolution of bacteria and coral has been proposed (Thompson et al, 2015), as it was demonstrated for Endozoicomonas symbionts in corals with contrasting life-history traits and across global scales (Bayer et al, 2013;Neave et al, 2016Neave et al, , 2017.…”