First identification of a fatal fungal infection of the marine sponge Chondrosia reniformis by Aspergillus tubingensis

Marine Mycobiomes Colonize Mediterranean Sponge Hosts in a Random Fashion

Marine sponges are widespread, sessile, filter-feeding animals, known for living in association with complex prokaryotic communities structured by host species. Though marine fungi are ubiquitous across marine environments, little is known about sponge-associated fungal communities (mycobiome). Indeed, aside from a few studies based on the isolation of fungal strains for biotechnological purposes, little information is available to understand the diversity and structure of sponge mycobiome. Here, a metabarcoding approach based on the ITS1 marker was applied to examine the structure and composition of fungal communities associated with four Mediterranean sponges. The species: Petrosia ficiformis, Chondrosia reniformis, Crambe crambe, and Chondrilla nucula were analyzed along with the surrounding seawater, revealing Aspergillus (1-56%), Cladosporium (1-75%), Malassezia (1-38.5%), and Pennicillium (1.5-36%) as the most represented fungal genera. Our data showed high intra-specific variability and no clear core mycobiome within each of the sponge species host, suggesting stochastic and perhaps transient community membership. This study sheds light on one of the most abundant yet least understood components of the marine ecosystem. Unraveling the dynamics of fungal interactions within sponge holobionts is essential to advance our understanding of their ecological roles and functions. By addressing the enigmatic nature of sponge-associated fungi, this research opens new avenues for exploring their contributions to marine ecosystems and resolving the many unanswered questions in this field.

From friends to foes: fungi could be emerging marine sponge pathogens under global change scenarios

Global change, experienced in the form of ocean warming and pollution by man-made goods and xenobiotics, is rapidly affecting reef ecosystems and could have devastating consequences for marine ecology. Due to their critical role in regulating marine food webs and trophic connections, sponges are an essential model for studying and forecasting the impact of global change on reef ecosystems. Microbes are regarded as major contributors to the health and survival of sponges in marine environments. While most culture-independent studies on sponge microbiome composition to date have focused on prokaryotic diversity, the importance of fungi in holobiont behavior has been largely overlooked. Studies focusing on the biology of sponge fungi are uncommon. Thus, our current understanding is quite limited regarding the interactions and “crosstalk” between sponges and their associated fungi. Anthropogenic activities and climate change may reveal sponge-associated fungi as novel emerging pathogens. Global change scenarios could trigger the expression of fungal virulence genes and unearth new opportunistic pathogens, posing a risk to the health of sponges and severely damaging reef ecosystems. Although ambitious, this hypothesis has not yet been proven. Here we also postulate as a pioneering hypothesis that manipulating sponge-associated fungal communities may be a new strategy to cope with the threats posed to sponge health by pathogens and pollutants. Additionally, we anticipate that sponge-derived fungi might be used as novel sponge health promoters and beneficial members of the resident sponge microbiome in order to increase the sponge's resistance to opportunistic fungal infections under a scenario of global change.

Microscopic marine invertebrates are reservoirs for cryptic and diverse protists and fungi

BACKGROUND

Microbial symbioses in marine invertebrates are commonplace. However, characterizations of invertebrate microbiomes are vastly outnumbered by those of vertebrates. Protists and fungi run the gamut of symbiosis, yet eukaryotic microbiome sequencing is rarely undertaken, with much of the focus on bacteria. To explore the importance of microscopic marine invertebrates as potential symbiont reservoirs, we used a phylogenetic-focused approach to analyze the host-associated eukaryotic microbiomes of 220 animal specimens spanning nine different animal phyla.

RESULTS

Our data expanded the traditional host range of several microbial taxa and identified numerous undescribed lineages. A lack of comparable reference sequences resulted in several cryptic clades within the Apicomplexa and Ciliophora and emphasized the potential for microbial invertebrates to harbor novel protistan and fungal diversity.

CONCLUSIONS

Microscopic marine invertebrates, spanning a wide range of animal phyla, host various protist and fungal sequences and may therefore serve as a useful resource in the detection and characterization of undescribed symbioses. Video Abstract.

Recent Advances of Marine Sponge-Associated Microorganisms as a Source of Commercially Viable Natural Products

Many industrially significant compounds have been derived from natural products in the environment. Research efforts so far have contributed to the discovery of beneficial natural products that have improved the quality of life on Earth. As one of the sources of natural products, marine sponges have been progressively recognised as microbial hotspots with reports of the sponges harbouring diverse microbial assemblages, genetic material, and metabolites with multiple industrial applications. Therefore, this paper aims at reviewing the recent literature (primarily published between 2016 and 2022) on the types and functions of natural products synthesised by sponge-associated microorganisms, thereby helping to bridge the gap between research and industrial applications. The metabolites that have been derived from sponge-associated microorganisms, mostly bacteria, fungi, and algae, have shown application prospects especially in medicine, cosmeceutical, environmental protection, and manufacturing industries. Sponge bacteria-derived natural products with medical properties harboured anticancer, antibacterial, antifungal, and antiviral functions. Efforts in re-identifying the origin of known and future sponge-sourced natural products would further clarify the roles and significance of microbes within marine sponges.

Transmission studies and the composition of prokaryotic communities associated with healthy and diseased Aplysina cauliformis sponges suggest that Aplysina Red Band Syndrome is a prokaryotic polymicrobial disease

Aplysina cauliformis, the Caribbean purple rope sponge, is commonly affected by Aplysina Red Band Syndrome. This transmissible disease manifests as circular lesions with red margins and results in bare spongin fibers. Leptolyngbya spp. appear to be responsible for the characteristic red coloration but transmission studies with a sponge-derived isolate failed to establish disease, leaving the etiology of ARBS unknown. To investigate the cause of ARBS, contact transmission experiments were performed between healthy and diseased sponges separated by filters with varying pore sizes. Transmission occurred when sponges were separated by filters with pore sizes ≥2.5 μm, suggesting a prokaryotic pathogen(s) but not completely eliminating eukaryotic pathogen(s). Using 16S rRNA gene sequencing methods, thirty-eight prokaryotic taxa were significantly enriched in diseased sponges, including Leptolyngbya, whereas seven taxa were only found in some, but not all, of the ARBS-affected sponges. These results do not implicate a single taxon, but rather a suite of taxa that changed in relative abundance with disease, suggesting a polymicrobial etiology as well as dysbiosis. As a better understanding of dysbiosis is gained, changes in the composition of associated prokaryotic communities may have increasing importance for evaluating and maintaining the health of individuals and imperiled coral reef ecosystems.

Detrimental conditions affecting Xestospongia muta across shallow and mesophotic coral reefs off the southwest coast of Puerto Rico

Sponges are fundamental components of coral reef communities and, unfortunately, like other major benthic members, they too have been impacted by epizootic and panzootic events. We report on the prevalence of disease-like conditions affecting populations of the giant barrel sponge Xestospongia muta across shallow and mesophotic coral reefs off La Parguera Natural Reserve (LPNR) and Mona Island Marine Reserve (MIMR) in Puerto Rico. Four different conditions affecting X. muta were observed during our surveys, of which 3 have been previously reported: cyclic spotted bleaching (CSB; apparently non-lethal), Xestospongia-tissue wasting disease (X-TWD; apparently lethal), and sponge orange band disease (SOB; sparsely associated with X-TWD infected individuals). Additionally, we describe a fourth condition, Xestospongia-tissue hardening condition (X-THC), a previously unreported disease recently observed along the insular shelf margin off LPNR and MIMR. Within LPNR, a total of 764 specimens of X. muta were inspected and measured. Of these, 590 sponges (72.2%) had CSB, 25 (3.27%) had signs of X-TWD, 7 (0.92%) had SOB, and the remaining 142 (18.6%) were apparently healthy. Three colonies inhabiting upper mesophotic depths on the LPNR insular shelf showed signs of CSB and X-TWD. At MIMR, video-transect surveys revealed a total of 514 colonies, of which 40 (7.78%) had signs of CSB and/or XTWD, 14 (2.72%) were affected by X-THC, while the remaining 460 (89.5%) showed no external signs of disease and appeared healthy. The presence of 4 concomitant disease-like conditions in barrel sponges of Puerto Rico is alarming, and indicative of the deteriorating status of Caribbean coral reefs.