Abstract
This paper describes the microbial community composition and genes for key metabolic genes, particularly the nitrogen fixation of the mucous-enveloped gut digesta of green (Lytechinus variegatus) and purple (Strongylocentrotus purpuratus) sea urchins by using the shotgun metagenomics approach. Both green and purple urchins showed high relative abundances of Gammaproteobacteria at 30% and 60%, respectively. However, Alphaproteobacteria in the green urchins had higher relative abundances (20%) than the purple urchins (2%). At the genus level, Vibrio was dominant in both green (~9%) and purple (~10%) urchins, whereas Psychromonas was prevalent only in purple urchins (~24%). An enrichment of Roseobacter and Ruegeria was found in the green urchins, whereas purple urchins revealed a higher abundance of Shewanella, Photobacterium, and Bacteroides (q-value < 0.01). Analysis of key metabolic genes at the KEGG-Level-2 categories revealed genes for amino acids (~20%), nucleotides (~5%), cofactors and vitamins (~6%), energy (~5%), carbohydrates (~13%) metabolisms, and an abundance of genes for assimilatory nitrogen reduction pathway in both urchins. Overall, the results from this study revealed the differences in the microbial community and genes designated for the metabolic processes in the nutrient-rich sea urchin gut digesta, suggesting their likely importance to the host and their environment.
Highlights
The intertidal and nearshore marine ecosystems of North America harbor a diverse community of invertebrates, vertebrates, and microorganisms, with primary producers such as drift and benthic macroalgae and kelp forests and seagrass meadows that constitute a dynamic aquatic food web [1,2,3,4]
The purple urchin digesta samples showed Gammaproteobacteria to be most abundant at ~60%, whereas Alphaproteobacteria was only represented at ~2%
Sample of green or purple sea urchin gut digesta at the phylum (e.g., Proteobacteria, Bacteroidetes, and Firmicutes) and the class levels (e.g., Gammaproteobacteria and Alphaproteobacteria) resulted from our study showed a similar trend in the gut of other
Summary
The intertidal and nearshore marine ecosystems of North America harbor a diverse community of invertebrates, vertebrates, and microorganisms, with primary producers such as drift and benthic macroalgae and kelp forests and seagrass meadows that constitute a dynamic aquatic food web [1,2,3,4]. These ecosystems are enriched with inorganic and organic nutrients that are produced and utilized by the resident organisms. In. North America, the green sea urchin, Lytechinus variegatus The grazing enables the sea urchins to metabolize and transform the ingested seagrass and macroalgal biomass into rich organic nutrients
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