The intestinal microbiome of vertebrates has been shown to play a crucial role in their digestive capabilities. This is particularly true for omnivores and herbivores that rely on enteric microbes to digest components of plant material that are indigestible by host-derived enzymes. While studies of microbe-host interactions are becoming more frequent in terrestrial systems, studies of this type are still limited in marine systems, particularly for higher trophic level organisms. Although sharks are largely carnivorous, the bonnethead shark (Sphyrna tiburo) has been identified as an omnivore, given that it assimilates seagrass material in addition to proteinaceous prey items such as crustaceans. The mechanisms by which bonnetheads digest seagrass, including microbial digestion, are still unknown. We use digestive enzyme assays, histological imaging, measurements of microbial fermentation, and 16S rDNA sequencing to explore potential processes by which the bonnethead shark may digest and assimilate plant material. We found evidence of microbial fermentation (as evident by moderate short-chain-fatty-acid concentrations) as well as evidence of greater epithelial surface area in their spiral intestine compared to other gut regions. We identified specific orders of microbes that make up the majority of the bonnethead shark gut microbiome (Vibrionales, Clostridiales, Pseudomonadales, Mycoplasmatales, Rhizobiales, and others), some of which are known, in other organisms, to be involved in the production of enzymes responsible for the breakdown of chitin (found in crustacean shells) and components of cellulose (found in seagrass). Our results highlight that an organism from a stereotypical “carnivorous” group is capable of breaking down seagrass, including potential for some fiber degradation, as well as advances our knowledge of gut microbe community structure in sharks.

脊椎动物的肠道微生物组已被证明在其消化能力中起着至关重要的作用。对于杂食性动物和食草动物而言，尤其如此，它们依靠肠内微生物来消化宿主来源的酶无法消化的植物材料成分。尽管在陆地系统中微生物与宿主之间相互作用的研究变得越来越频繁，但这种类型的研究在海洋系统中仍然是有限的，特别是对于营养级别较高的生物而言。尽管鲨鱼大部分是肉食性的，但the头鲨（Sphyrna tiburo）已被确认为杂食动物，因为它除了吸收甲壳类等蛋白质猎物外，还吸收了海草物质。net虫消化海草的机制（包括微生物消化）仍然未知。我们使用消化酶分析，组织学成像，微生物发酵测量和16S rDNA测序来探索潜在的过程，其中net鱼可能会消化和吸收植物材料。我们发现微生物发酵的证据（通过适度的短链脂肪酸浓度得到证明）以及与其他肠道区域相比在螺旋肠中的上皮表面积更大的证据。我们确定了构成bonnethead鲨鱼肠肠道微生物组（Vibrionales，Clostridiales，Pseudomonadales，Mycoplasmatales，根瘤菌等），其中一些在其他生物体中，与参与分解几丁质（在甲壳类动物壳中发现）和纤维素成分（在海草中）有关的酶的产生有关。我们的研究结果表明，定型“食肉”类中的一种生物能够分解海草，包括某些纤维降解的潜力，并提高了我们对鲨鱼肠道微生物群落结构的认识。