Biology subjects

Weiler, B. A.

Publications and source records attributed to Weiler, B. A..

5 recordsLinked to original sources

bioRxiv2026

Global distribution and host specificity of plastid-bearing microeukaryotes across coral holobionts

Corals form intricate symbiotic relationships with diverse microbial communities that influence their physiology, evolution, and ecological function. In 16S rRNA gene microbiome analyses, sequences taxonomically assigned to chloroplasts are often discarded as noise, yet they contain valuable ecological information. Here we present a meta-analysis of publicly available 16S rRNA gene datasets examining the diversity and global distribution of plastid-bearing microeukaryotic symbionts in corals. We reprocessed 2,679 samples from 45 studies, generating a dataset of 10,950 amplicon sequence variants (ASVs) from 13 million read pairs across 73 coral species, 23 families, all major oceanic regions, and three host health states. Corallicolida and Ostreobium were highly abundant across all coral lineages, health states, and locations, confirming them as the most widespread plastid-bearing coral symbionts after the Symbiodiniaceae. The most abundant ASVs exhibited strong host specificity, with most sequences restricted to specific coral lineages, a pattern consistent with phylosymbiosis, and supported across the full dataset by ASV-level community profiles. Phylogenetic placement of apicomplexan reads classified most of them as Corallicolida and revealed ASVs consistent with a novel apicomplexan-related lineage, tentatively designated ARL-XXI. Six distinct Ostreobium clades were recovered, three described here for the first time, with the North West Pacific emerging as a potential hotspot of Ostreobium diversity. Together, these results highlight the value of retaining plastid-derived sequences and underscore the importance of microeukaryotic-inclusive molecular surveys for understanding the ecological dynamics of the coral holobiont.

microbiology↗

bioRxiv2026

Global diversity and distribution of coral-associated protists

Coral reefs are critical ecosystems and biodiversity hotspots that provide ecological stability and essential services to coastal communities. The coral holobiont, a complex symbiotic system composed of the coral animal and a diverse array of associated microbes, plays a central role in coral health and resilience. While Symbiodiniaceae and bacterial symbionts have been extensively studied, much less is known about the diversity and function of microbial eukaryotes such as protists and fungi. These organisms are increasingly recognized as important, yet remain vastly underexplored. Here, we present the first global survey of the coral-associated eukaryome using an anti-metazoan 18S rRNA primer set to bypass host DNA amplification. Our dataset includes corals and related anthozoans from the Caribbean Sea, the Red Sea, and several locations in the Pacific Ocean, spanning a broad taxonomic and geographic range, and includes both healthy and diseased specimens. They reveal a eukaryome that is not only more diverse than that of global coastal waters but also surpasses the diversity of the well-studied coral bacterial microbiome. We recover diverse microbial eukaryotic communities, including Symbiodiniaceae, other known symbionts, potential pathogens, and previously uncharacterized lineages. These results reveal consistent patterns across coral groups and geographic regions. This study provides the most comprehensive taxonomic overview of coral-associated microbial eukaryotes to date, offering new insights into their roles within the holobiont. Our findings highlight the ecological significance of microbial eukaryotes and underscore the importance of incorporating them into broader coral reef research and conservation strategies.

microbiology↗

bioRxiv2025

Temporal transcriptional rhythms govern coral-symbiont function and microbiome dynamics

Diel rhythms align physiological processes with light/dark cycles, driving predictable oscillations in gene expression and protein activity through tightly controlled transcriptional-translational feedback loops. Transcriptomic analyses in the stony coral Pseudodiploria strigosa revealed tightly regulated transcriptional control: dawn triggers a molecular reset marked by RNA metabolism and protein turnover; midday emphasizes anabolic and phosphate-regulated pathways; dusk reflects transitional lipid and amino acid metabolism; and midnight reveals stress-responses, mRNA catabolism, and mitochondrial organization. The photosymbiont Breviolum sp. exhibits subtler but distinct diel regulation, with photoprotective activation at dawn, metabolite transport and nitrogen cycling through midday and dusk, and cell cycle and ion homeostasis at night. Microbial communities show time-dependent restructuring of co-occurrence networks. Carbohydrate-catabolizing taxa associated with Symbiodiniaceae during daylight, while nighttime assemblages feature methylotrophs likely facilitating dimethylsulfoniopropionate (DMSP) metabolism. Together, these findings present the first system-level molecular framework of diel regulation across the coral-photosymbiont-microbe holobiont, revealing strong time-specific transcriptional control as a key driver of coordinated function and homeostasis. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=190 SRC="FIGDIR/small/668741v1_ufig1.gif" ALT="Figure 1"> View larger version (61K): org.highwire.dtl.DTLVardef@1cb5740org.highwire.dtl.DTLVardef@cd58ceorg.highwire.dtl.DTLVardef@1815777org.highwire.dtl.DTLVardef@9550a8_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

Fireworms (Hermodice carunculata) are a reservoir and potential vector for coral-infecting apicomplexans

Corals (Cnidaria; Anthozoa) play critical roles as habitat-forming species with a wide range, from warm shallow-water tropical coral reefs to cold-water ecosystems [1-3]. They also represent a complex ecosystem as intricate holobionts made up of microbes from all domains of the Tree of Life, that can play significant roles in host health and fitness [4]. The corallicolids are a clade of apicomplexans that infect a wide variety of anthozoans across the world, and can influence the thermal tolerance of habitat-forming corals [1, 5]. Despite their potentially important impacts on reef ecosystems, much of the basic biology and ecology of corallicolids remains unclear. Apicomplexans often have a closed life cycle, with minimal environmental exposure, and sometimes multiple hosts. Corallicolids have only been documented in anthozoan hosts, with no known secondary/reservoir hosts or vectors [6]. Here, we show that abundant corallicolid sequences are recovered from bearded fireworms (Hermodice carunculata) in tropical reef habitats off Curacao, and that they are distinct from corallicolids infecting the corals on which the fireworms were feeding at the time of their collection. The data are consistent with an active infection of fireworms, as opposed to corallicolids being a byproduct of feeding on infected corals, and we suggest that H. carunculata is potentially a vector moving corallicolids among coral hosts through its faeces. These findings not only expand our understanding of the ecological interactions within coral reef ecosystems but also highlight the potential role of host-associated parasites in shaping the resilience of reef habitats.

microbiology↗

bioRxiv2020

Mediocremonas mediterraneus, a New Member within the Developea

The Stramenopiles are a large and diverse group of eukaryotes that possess various lifestyles required to thrive in a broad array of environments. The stramenopiles branch with the alveolates, rhizarians, and telonemids, forming the supergroup TSAR. Here, we present a new genus and species of aquatic nanoflagellated stramenopile: Mediocremonas mediterraneus, a free-swimming heterotrophic predator. M. mediterraneus cell bodies measure between 2.0-4.0 m in length and 1.2-3.7 m in width, possessing two flagella and an oval body morphology. The growth and grazing rate of M. mediterraneus in batch cultures ranges from 0.68 to 1.83 d-1 and 1.99 to 5.38 bacteria h-1, respectively. M. mediterraneus was found to be 93.9% phylogenetically similar with Developayella elegans and 94.7% with Develorapax marinus, two members within the class Developea. The phylogenetic position of the Developea and the ability of M. mediterraneus to remain in culture makes it a good candidate for further genomic studies that could help us to better understand phagotropy in marine systems as well as the transition from heterotrophy to phototrophy within the stramenopiles.

microbiology↗