Abstract
In the present work, culture-based and culture-independent investigations were performed to determine the microbiota structure of the coelomic fluid of Mediterranean sea urchin Paracentrotus lividus individuals collected from two distinct geographical sites neighboring a high-density population bay and a nature reserve, respectively. Next Generation Sequencing analysis of 16S rRNA gene (rDNA) showed that members of the Proteobacteria, Bacteroidetes and Fusobacteria phyla, which have been previously reported to be commonly retrieved from marine invertebrates, dominate the overall population of microorganisms colonizing this liquid tissue, with minority bacterial genera exhibiting remarkable differences among individuals. Our results showed that there is a correlation between microbiota structure and geographical location of the echinoderm collection site, highlighting over-representation of metagenomic functions related to amino acid and bioactive peptides metabolism in specimens inhabiting the nature reserve. Finally, we also described the developmental delay and aberrations exhibited by sea urchin embryos exposed to distinct bacterial isolates, and showed that these defects rely upon hydrophilic compound(s) synthesized by the bacterial strains assayed. Altogether, our findings lay the groundwork to decipher the relationships of bacteria with sea urchins in their aquatic environment, also providing an additional layer of information to understand the biological roles of the coelomic fluid.
Highlights
In the present work, culture-based and culture-independent investigations were performed to determine the microbiota structure of the coelomic fluid of Mediterranean sea urchin Paracentrotus lividus individuals collected from two distinct geographical sites neighboring a high-density population bay and a nature reserve, respectively
Based on the notion that the cultivability of marine microbial communities often ranges below 10% of total b acteria[44,45], to obtain a comprehensive understanding of the microbiota structure we performed an analysis based on Generation Sequencing of V3-V4 region amplicons of 16S rDNA obtained from metagenomic DNA extracted from coelomic fluid of six P. lividus individuals from site A and four from site B (Supplementary Fig. S1, Table S1)
Enomoto et al.[37] reported a distinctive bacterial microbiota structure in the coelomic fluid of distinct holothurian individuals. These findings, coupled to the fact that the perivisceral liquid of echinoderms is in dynamic equilibrium with the surrounding seawater environment[53], raise questions about the stability of the microbiota composition in the coelomic fluid of individual sea urchins across seasons and geographic sites. This point has been addressed in the present study by describing and comparatively analysing the bacterial microbiota residing in the coelomic fluid of sea urchins collected from two distinct geographical sites
Summary
Culture-based and culture-independent investigations were performed to determine the microbiota structure of the coelomic fluid of Mediterranean sea urchin Paracentrotus lividus individuals collected from two distinct geographical sites neighboring a high-density population bay and a nature reserve, respectively. Sea urchins are invertebrate animals distributed throughout the oceans of the world, where they represent central players in many benthic ecosystems Besides their ecological role and economic importance as fishery products[20], sea urchins have been used as model organisms for biological research for nearly two centuries, contributing significantly to our understanding of fertilization, molecular embryology, gene regulation, cell cycle regulation, evolution, population genetics, and toxicology[21,22,23,24,25,26]. The reason of their extensive use as experimental model likely relies in their phylogenetic position. Sea urchins are basal deuterostomes belonging to Echinodermata, the sister phylum to the c hordates[27], and they are closely related to humans[28]
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