Successional Changes of Microbial Communities and Host-Microbiota Interactions Contribute to Dietary Adaptation in Allodiploid Hybrid Fish

Acute copper oxide nanoparticles exposure alters zebrafish larval microbiome

Copper oxide nanoparticles (CuO NPs) are being used in healthcare industries due to its antimicrobial properties. The increased consumption of NPs could lead to the rise of these NPs in the environment affecting the biological systems. Altered microbiome has been correlated to disease pathology in humans as well as xenobiotic toxicity in experimental animal models. However, CuO NPs-induced microbiome alterations in vertebrates have not been reported so far. In this study, for the first time, zebrafish larvae at 96 hpf (hours post fertilization) were exposed to CuO NPs for 24 h at 10, 20, and 40 ppm. After exposure, the control and treated larvae were subjected to 16S rRNA amplicon sequencing followed by relative taxa abundance, alpha and beta diversity analysis, single factor analysis, LEfSe, Deseq2, and functional profiling. No significant alteration was detected in the microbial richness and diversity, however, specific taxa constituting the core microbiome such as phylum Proteobacteria were significantly increased and Bacterioidetes and Firmicutes were decreased in the treated groups, indicating a core microbiota dysbiosis. Further, the family Lachnospiraceae, and genus Syntrophomonas involved in butyrate production and the metabolism of lipids and glucose were significantly altered. In addition, the opportunistic pathogens belonging to order Flavobacteriales were increased in CuO NPs treated groups. Moreover, the taxa involved in host immune response (Shewanella, Delftia, and Bosea) were found to be enriched in CuO NPs exposed larvae. These results indicate that CuO NPs exposure causes alteration in the core microbiota, which could cause colitis or inflammatory bowel disease.

Toxicity comparison of perfluorooctanoic acid (PFOA), hexafluoropropylene oxide dimer acid (HFPO-DA), and hexafluoropropylene oxide trimer acid (HFPO-TA) in zebrafish gut

Hexafluoropropylene oxide dimer acid (HFPO-DA) and hexafluoropropylene oxide trimer acid (HFPO-TA) are considered as alternatives to perfluorooctanoic acid (PFOA). In this study, zebrafish were exposed to different concentrations of PFOA, HFPO-DA, and HFPO-TA (5 μg/L and 500 μg/L), and the toxic effects on oxidative damage, inflammation, and cell apoptosis in the gut were compared. Additionally, changes in gut metabolome profiles and microbial community structure were analyzed. The results revealed that exposures to HFPO-DA and HFPO-TA led to lower levels of oxidative damage compared to PFOA exposure. However, all three treatments had comparable effects on inflammation and apoptosis. The main biological pathways affected by all three exposures were lipid metabolism, nucleotide metabolism, amino acid metabolism, and environmental information processing. The effects on metabolome profiles were much higher for HFPO-DA and HFPO-TA compared to PFOA at a concentration of 5 μg/L. At a concentration of 500 μg/L, HFPO-DA and HFPO-TA showed similar effects to PFOA. This study also examined the Pearson correlations between gut microbiota and the toxic effects mentioned above. The abundance of specific apoptosis-related genera differed among the three target chemicals, suggesting they may act differently in inducing apoptosis. The correlations between HFPO-DA and HFPO-TA were mostly similar, which helps explain the similar effects observed in their respective treatment groups on metabolic profiles. Overall, this study indicates that HFPO-DA and HFPO-TA may not be safe alternatives to PFOA and provides valuable insights into their toxic effects and risk assessment in water environments.

The Effect of the Microalgae Chlorella vulgaris on the Gut Microbiota of Juvenile Nile Tilapia (Oreochromis niloticus) Is Feeding-Time Dependent

Chlorella vulgaris is one of the most commonly used microalgae in aquaculture feeds. It contains high concentrations of various kinds of nutritional elements that are involved in the physiological regulation of aquaculture animals. However, few studies have been conducted to illustrate their influence on the gut microbiota in fish. In this work, the gut microbiota of Nile tilapia (Oreochromis niloticus) (average weight is 6.64 g) was analyzed by high-throughput sequencing of the 16S rRNA gene after feeding with 0.5% and 2% C. vulgaris additives in diets for 15 and 30 days (average water temperature was 26 °C). We found that the impact of C. vulgaris on the gut microbiota of Nile tilapia was feeding-time dependent. Only by feeding for 30 days (not 15 days) did the addition of 2% C. vulgaris to diets significantly elevate the alpha diversity (Chao1, Faith pd, Shannon, Simpson, and the number of observed species) of the gut microbiota. Similarly, C. vulgaris exerted a significant effect on the beta diversity (Bray-Curtis similarity) of the gut microbiota after feeding for 30 days (not 15 days). During the 15-day feeding trial, LEfSe analysis showed that Paracoccus, Thiobacillus, Dechloromonas, and Desulfococcus were enriched under 2% C. vulgaris treatment. During the 30-day feeding trial, Afipia, Ochrobactrum, Polymorphum, Albidovulum, Pseudacidovorax, and Thiolamprovum were more abundant in 2% C. vulgaris-treated fish. C. vulgaris promoted the interaction of gut microbiota in juvenile Nile tilapia by increasing the abundance of Reyranella. Moreover, during the feeding time of 15 days, the gut microbes interacted more closely than those during the feeding time of 30 days. This work will be valuable for understanding how C. vulgaris in diets impacts the gut microbiota in fish.

Host Hybridization Dominates over Cohabitation in Affecting Gut Microbiota of Intrageneric Hybrid Takifugu Pufferfish

Microbial symbionts are of great importance for macroscopic life, including fish, and both collectively comprise an integrated biological entity known as the holobiont. Yet little is known as to how the normal balance within the fish holobiont is maintained and how it responds to biotic and/or abiotic influences. Here, through amplicon profiling, the genealogical relationship between artificial F1 hybrid pufferfish with growth heterosis, produced from crossing female Takifugu obscurus with male Takifugu rubripes and its maternal halfsibling purebred, was well recapitulated by their gut microbial community similarities, indicating an evident parallelism between host phylogeny (hybridity) and microbiota relationships therein. Interestingly, modest yet significant fish growth promotion and gut microbiota alteration mediated by hybrid-purebred cohabitation were observed, in comparison with their respective monoculture cohorts that share common genetic makeups, implying a certain degree of environmental influences. Moreover, the underlying assemblage patterns of gut microbial communities were found associated with a trade-off between variable selection and dispersal limitation, which are plausibly driven by the augmented social interactions between hybrid and purebred cohabitants differing in behaviors. Results from this study not only can enrich, from a microbial perspective, the sophisticated understanding of complex and dynamic assemblage of the fish holobiont, but will also provide deeper insights into the ecophysiological factors imposed on the diversity-function relationships thereof. Our findings emphasize the intimate associations of gut microbiota in host genetics-environmental interactions and would have deeper practical implications for microbial contributions to optimize performance prediction and to improve the production of farmed fishes. IMPORTANCE Microbial symbionts are of great importance for macroscopic life, including fish, and yet little is known as to how the normal balance within the fish holobiont is maintained and how it responds to the biotic and/or abiotic influences. Through gut microbiota profiling, we show that host intrageneric hybridization and cohabitation can impose a strong disturbance upon pufferfish gut microbiota. Moreover, marked alterations in the composition and function of gut microbiota in both hybrid and purebred pufferfish cohabitants were observed, which are potentially correlated with different metabolic priorities and behaviors between host genealogy. These results can enrich, from a microbial perspective, the sophisticated understanding of the complex and dynamic assemblage of the fish holobiont and would have deeper practical implications for microbial contributions to optimize performance prediction and to improve farmed fish production.

Research Progress of the Gut Microbiome in Hybrid Fish

Fish, including hybrid species, are essential components of aquaculture, and the gut microbiome plays a vital role in fish growth, behavior, digestion, and immune health. The gut microbiome can be affected by various internal and/or external factors, such as host development, diet, and environment. We reviewed the effects of diet and dietary supplements on intestinal microorganisms in hybrid fish and the difference in the gut microbiome between the hybrid and their hybrids that originate. Then, we summarized the role of the gut microbiome in the speciation and ecological invasion of hybrid fish. Finally, we discussed possible future studies on the gut microbiome in hybrid fish, including the potential interaction with environmental microbiomes, the effects of the gut microbiome on population expansion, and fish conservation and management.