microbiome

Community structure of coral microbiomes is dependent on host morphology

Abstract

Background: The importance of symbiosis has long been recognized on coral reefs, where the photosynthetic dinof lagellates of corals (Symbiodiniaceae) are the primary symbiont. Numerous studies have now shown that a diverse assemblage of prokaryotes also make-up part of the microbiome of corals. A subset of these prokaryotes is capable of f ixing nitrogen, known as diazotrophs, and is also present in the microbiome of scleractinian corals where they have been shown to supplement the holobiont nitrogen budget. Here, an analysis of the microbiomes of 16 coral species collected from Australia, Curaçao, and Hawai’i using three different marker genes (16S rRNA, nifH, and ITS2) is presented. These data were used to examine the effects of biogeography, coral traits, and ecological life history characteristics on the composition and diversity of the microbiome in corals and their diazotrophic communities.

Results: The prokaryotic microbiome community composition (i.e., beta diversity) based on the 16S rRNA gene varied between sites and ecological life history characteristics, but coral morphology was the most significant factor affecting the microbiome of the corals studied. For 15 of the corals studied, only two species Pocillopora acuta and Seriotopora hystrix, both brooders, showed a weak relationship between the 16S rRNA gene community structure and the diazotrophic members of the microbiome using the nifH marker gene, suggesting that many corals support a microbiome with diazotrophic capabilities. The order Rhizobiales, a taxon that contains primarily diazotrophs, are common members of the coral microbiome and were eight times greater in relative abundances in Hawai’i compared to corals from either Curacao or Australia. However, for the diazotrophic component of the coral microbiome, only host species significantly influenced the composition and diversity of the community.

Conclusions: The roles and interactions between members of the coral holobiont are still not well understood, especially critical functions provided by the coral microbiome (e.g., nitrogen fixation), and the variation of these functions across species. The findings presented here show the significant effect of morphology, a coral “super trait,” on the overall community structure of the microbiome in corals and that there is a strong association of the diazotrophic community within the microbiome of corals. However, the underlying coral traits linking the effects of host species on diazotrophic communities remain unknown.

Date
2022
Data type
Scientific article
Theme
Research and monitoring
Journal
Geographic location
Curacao

Distinct Microbiomes in three Tropical seagrasses around the island of Curaçao: Halophila stipulacea, Halodule wrightii and Thalassia testudinum

Seagrasses represent the unique re-colonization of the marine ecosystem by angiosperms. As their terrestrial relatives, seagrasses are important habitat providers but in contrast, their microbiomes are still poorly known. The microbial community associated with terrestrial plants is intensively studied and plays an important role in plant fitness. The close relation of seagrasses to terrestrial plants suggests a resemblance in survival strategies, including the creation of a microbiome distinct of the surrounding environment. To obtain more knowledge regarding seagrass microbiomes and their intra- and interspecies differentiation, samples of three tropical seagrass species occurring around the island of Curaçao, the invasive Halophila stipulacea and the natives Halodule wrightii and Thalassia testudinum, were collected. Root and leaf-associated microbes were separately analyzed using high throughput Illumina sequencing of the region V5-V7 of the 16S rRNA gene. Sequences were aligned and clustered into Operational Taxonomic Units (OTUs). Results displayed the occurrence of a seagrass-specific microbiome, distinct from that of the surrounding seawater and sediment. The existence of a species and tissue (root/leaf) specific bacterial community and structure was detected, along with a bacterial community that was shared among the seagrasses. OTUs belonging to the shared seagrass community were mostly of the orders rhizobiales. Desulfobacterales was the most abundant order associated with the roots and Rhodobacterales with the leaves of the three seagrass species. Species-specific bacteria are represented mostly by OTUs of the same orders as the common OTUs, along with a few species-specific orders. The high abundant and widespread bacterial OTUs were identified to be mostly associated with sulfur and nitrogen cycling, which point towards the importance of these processes in seagrass fitness.

Date
2018
Data type
Research report
Theme
Research and monitoring
Report number
Student Thesis
Geographic location
Curacao
Author