Epiconone, one novel cyclohexenone from endophytic fungi Epicoccum sp. 1-042
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The succession of epiphytic microalgae conditions fungal community composition: how chytrids respond to blooms of dinoflagellates
This study aims to investigate the temporal dynamics of the epiphytic protist community on macroalgae, during the summer months, with a specific focus on fungi, and the interactions between zoosporic chytrid parasites and the proliferation of the dinoflagellates. We employed a combination of environmental sequencing techniques, incubation of natural samples, isolation of target organisms and laboratory experiments. Metabarcoding sequencing revealed changes in the dominant members of the epiphytic fungal community. Initially, fungi comprised < 1% of the protist community, mostly accounted for by Basidiomycota and Ascomycota, but with the emergence of Chytridiomycota during the mature phase of the biofilm, the fungal contribution increased to almost 30%. Chytridiomycota became dominant in parallel with an increase in the relative abundance of dinoflagellates in the community. Microscopy observations showed a general presence of chytrids following the peak proliferation of the dinoflagellate Ostreopsis sp., with the parasite, D. arenysensis as the dominant chytrid. The maximum infection prevalence was 2% indicating host-parasite coexistence. To further understand the in-situ prevalence of chytrids, we characterised the dynamics of the host abundance and prevalence of chytrids through co-culture. These laboratory experiments revealed intraspecific variability of D. arenysensis in its interaction with Ostreopsis, exhibiting a range from stable coexistence to the near-extinction of the host population. Moreover, while chytrids preferentially parasitized dinoflagellate cells, one of the strains examined displayed the ability to utilize pollen as a resource to maintain its viability, thus illustrating a facultative parasitic lifestyle. Our findings not only enrich our understanding of the diversity, ecology, and progression of epiphytic microalgal and fungal communities on Mediterranean coastal macroalgae, but they also shed light on the presence of zoosporic parasites in less-explored benthic habitats.
Controlling noise with self-organized resetting
Biological systems often consist of a small number of constituents and are therefore inherently noisy. To function effectively, these systems must employ mechanisms to constrain the accumulation of noise. Such mechanisms have been extensively studied and comprise the constraint by external forces, nonlinear interactions, or the resetting of the system to a predefined state. Here, we propose a fourth paradigm for noise constraint: self-organized resetting, where the resetting rate and position emerge from self-organization through time-discrete interactions. We study general properties of self-organized resetting systems using the paradigmatic example of cooperative resetting, where random pairs of Brownian particles are reset to their respective average. We demonstrate that such systems undergo a delocalization phase transition, separating regimes of constrained and unconstrained noise accumulation. Additionally, we show that systems with self-organized resetting can adapt to external forces and optimize search behavior for reaching target values. Self-organized resetting has various applications in nature and technology, which we demonstrate in the context of sexual interactions in fungi and spatial dispersion in shared mobility services. This work opens routes into the application of self-organized resetting across various systems in biology and technology.
Soil bacterium manipulates antifungal weapons by sensing intracellular type IVA secretion system effectors of a competitor
Soil beneficial bacteria can effectively inhibit bacterial pathogens by assembling contact-dependent killing weapons, such as the type IVA secretion system (T4ASS). It’s not clear whether these antibacterial weapons are involved in biotrophic microbial interactions in soil. Here we showed that an antifungal antibiotic 2,4-DAPG production of the soil bacterium, Pseudomonas protegens can be triggered by another soil bacterium, Lysobacter enzymogenes, via T4ASS by co-culturing on agar plates to mimic cell-to-cell contact. We demonstrated that the induced 2,4-DAPG production of P. protegens is achieved by intracellular detection of the T4ASS effector protein Le1519 translocated from L. enzymogenes. We defined Le1519 as LtaE (Lysobacter T4E triggering antifungal effects), which specifically stimulates the expression of 2,4-DAPG biosynthesis genes in P. protegens, thereby protecting soybean seedlings from infection by the fungus Rhizoctonia solani. We further found that LtaE directly bound to PhlF, a pathway-specific transcriptional repressor of the 2,4-DAPG biosynthesis, then activated the 2,4-DAPG production. Our results highlight a novel pattern of microbial interspecies and interkingdom interactions, providing a unique case for expanding the diversity of soil microbial interactions.
Associations of Batrachochytrium dendrobatidis with skin bacteria and fungi on Asian amphibian hosts
Amphibian skin harbors microorganisms that are associated with the fungal pathogen Batrachochytrium dendrobatidis (Bd), which causes chytridiomycosis, one of the most significant wildlife diseases known. This pathogen originated in Asia, where diverse Bd lineages exist; hence, native amphibian hosts have co-existed with Bd over long time periods. Determining the nuances of this co-existence is crucial for understanding the prevalence and spread of Bd from a microbial context. However, associations of Bd with the natural skin microbiome remain poorly understood for Asian hosts, especially in relation to skin-associated fungi. We used 16 S rRNA and fungal internal transcribed spacer (ITS) gene sequencing to characterize the skin microbiome of four native Asian amphibian species and examined the relationships between Bd infection and their skin bacterial and fungal communities; we also analyzed the correlates of the putative anti-Bd bacteria. We show that both skin bacterial and fungal community structure and composition had significant associations with infection status (Bd presence/absence) and infection intensity (frequency of Bd sequence reads). We also found that the putative anti-Bd bacterial richness was correlated with Bd infection status and infection intensity, and observed that the relative abundance of anti-Bd bacteria roughly correspond with changes in both Bd prevalence and mean infection intensity in populations. Additionally, the microbial co-occurrence network of infected frogs was significantly different from that of uninfected frogs that were characterized by more keystone nodes (connectors) and larger proportions in correlations between bacteria, suggesting stronger inter-module bacterial interactions. These results indicate that the mutual effects between Bd and skin-associated microbiome, including the interplay between bacteria and fungi, might vary with Bd infection in susceptible amphibian species. This knowledge will help in understanding the dynamics of Bd from a microbial perspective, potentially contributing to mitigate chytridiomycosis in other regions of the world.
Extreme drought-heatwave events threaten the biodiversity and stability of aquatic plankton communities in the Yangtze River ecosystems
Rivers are crucial to biogeochemical cycles, connecting terrestrial, oceanic, and atmospheric systems. However, their ecosystems are increasingly threatened by extreme weather events. Here we used the environmental DNA approach to assess the impact of extreme drought-heatwave events on the aquatic plankton communities of the Yangtze River. We showed that an extreme drought-heatwave event reduced the α diversity of communities, increased their β diversity, and simultaneously simplified and destabilized community network structure. This event also shifted the dominant algae taxa from Bacillariophyta to Cyanobacteria, accompanied by increases in organic carbon and labile organic carbon contents. Globally, temperature rises during this extreme drought-heatwave event are more pronounced in high-latitude regions, likely amplifying impacts on river ecosystem biodiversity and stability. Our findings highlight the vulnerability of river ecosystems to extreme events and underscore the need to mitigate climate change’s effects on river ecosystems.
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