Microbial Composition and Genes for Key Metabolic Attributes in the Gut Digesta of Sea Urchins Lytechinus variegatus and Strongylocentrotus purpuratus Using Shotgun Metagenomics

Effect of harvesting season and location on the microbial quality and community composition of the edible sea urchin (Echinus esculentus) gonads

Despite the crucial role of microbial community composition in the quality and stability of seafood, little emphasis has been given to the microbiota profile of sea urchin gonads. This study investigates the microbial quality and community composition of sea urchin gonads (Echinus esculentus) as a function of harvesting season (autumn, winter, spring, and summer) and location (one site proximal to urban activity areas while the other is located in open water close to the coastline). Significant season-dependent variations were found in psychrotrophic and aerobic plate counts, with higher counts in summer, followed by autumn, spring, and winter. H2S-producing bacteria and Pseudomonas spp. counts were unaffected by harvesting season or location. Sea urchin gonad microbial composition proved resilient and dynamic, primarily shaped by seasonal variations, and minimally influenced by location. Winter and spring samples exhibited higher diversity than autumn and summer. Key genera like Pseudomonas, Psychromonas, Vibrio, Chryseobacterium, Shewanella, and Photobacterium varied seasonally. Pseudomonas, Vibrio, and Photobacterium are crucial in assessing microbial quality and safety due to their roles as specific spoilage organisms (SSOs) and, in some cases, human pathogens. Though relative abundances differed slightly between locations, harvesting location did not notably impact microbial community shaping in gonads. However, the results suggest that harvesting locations near areas with urban activity may lead to contamination with specific bacterial species, possibly due to water quality variations. These findings emphasize the importance of considering seasonality when evaluating sea urchin gonad microbial quality. Identifying key genera enhances insights into potential SSOs and human pathogens, enhancing food safety considerations in the consumption of raw or lightly processed sea urchin gonads and guiding the development of preservation methods to extend shelf life.

Spotting disease disrupts the microbiome of infected purple sea urchins, Strongylocentrotus purpuratus

BACKGROUND

Spotting disease infects a variety of sea urchin species across many different marine locations. The disease is characterized by discrete lesions on the body surface composed of discolored necrotic tissue that cause the loss of all surface appendages within the lesioned area. A similar, but separate disease of sea urchins called bald sea urchin disease (BSUD) has overlapping symptoms with spotting disease, resulting in confusions in distinguishing the two diseases. Previous studies have focus on identifying the underlying causative agent of spotting disease, which has resulted in the identification of a wide array of pathogenic bacteria that vary based on location and sea urchin species. Our aim was to investigate the spotting disease infection by characterizing the microbiomes of the animal surface and various tissues.

RESULTS

We collected samples of the global body surface, the lesion surface, lesioned and non-lesioned body wall, and coelomic fluid, in addition to samples from healthy sea urchins. 16S rRNA gene was amplified and sequenced from the genomic DNA. Results show that the lesions are composed mainly of Cyclobacteriaceae, Cryomorphaceae, and a few other taxa, and that the microbial composition of lesions is the same for all infected sea urchins. Spotting disease also alters the microbial composition of the non-lesioned body wall and coelomic fluid of infected sea urchins. In our closed aquarium systems, sea urchins contracted spotting disease and BSUD separately and therefore direct comparisons could be made between the microbiomes from diseased and healthy sea urchins.

CONCLUSION

Results show that spotting disease and BSUD are separate diseases with distinct symptoms and distinct microbial compositions.

Microbiome modulation, microbiome protein metabolism index, and growth performance of broilers supplemented with a precision biotic

The objectives of the present studies were to evaluate: 1) the in vivo impact of the supplementation with a precision biotic (PB) on the growth performance and microbiome modulation of broiler chickens; 2) the role of PB on the modulation of functional pathways of the microbiome collected from animals with low and high body weight gain, and 3) to develop a Microbiome Protein Metabolism Index (MPMI) derived from gut metagenomic data to link microbial protein metabolism with performance. The in vivo work consisted of 2 experiments with 2 treatments: Control vs. PB at 1.1 kg/MT of PB with 21 or 14 replicates of 40 birds per replicate, in experiments 1 and 2, respectively. Growth performance was evaluated in both experiments, and from experiment 1, cecal samples from one bird/replicate was collected on d 21 and 42 (n = 21/treatment) to evaluate the microbiome through whole genome sequencing. In the ex vivo assay, 6 cecal samples were collected from low body weight (BW) birds (at 10% below average), and 6 samples from high BW birds (at least 10% above average). The samples were incubated in the presence or absence of PB. After incubation, DNA was isolated to develop a functional genomic assay and the supernatant was separated to measure short-chain fatty acid (SCFA) production. The MPMI is the sum of beneficial genes in the pathways related to protein metabolism. In the in vivo grow out experiments, it was observed that the supplementation improved the BW gain by 3% in both studies, and the corrected feed conversion ratio (cFCR) by 3.7 and 3.4% in studies 1 and 2, respectively (P < 0.05). The functional microbiome analysis revealed that the PB shifted the microbiome pathways toward a beneficial increase in protein utilization, as shown by higher MPMI. In the ex vivo experiment, the PB increased the abundance of genes related to the beneficial metabolism of protein (quantitative MPMI), and the concentration of SCFA, regardless of the underline BW of the birds. Taken together, the microbiome metabolic shift observed in the in vivo study and higher MPMI, plus the observations from the ex vivo assay with higher SFCA production, may explain the improvement in growth performance obtained with the supplementation of PB.