产蛋鸡肠道菌群通过有机基质代谢调控鸡蛋蛋壳矿化的机制

Huge economic loss due to egg breakage is a chronic problem to the poultry production. The strategies that would increase eggshell quality could be of considerable value to egg producers and poultry industry. The ultrastructure of an eggshell is considered the major determinant of its quality. Study on eggshell ultrastructure and improvement has been our research focus in our group in recent five years. Our previous research showed that the poorer shell strength and textural properties in eggs laid by old hens could be due to changes in eggshell ultrastructural organization and organic matrix metabolism associated with ageing of the hens. We had conducted several trials in laying hens, and found that the direct supplementation of beneficial probiotic bacteria can improve eggshell quality by modulating mechanical and ultrastructural changes, but how the microbiome can affect eggshell mineralization and eggshell gland distant from the gut is not well understood. Therefore, we propose to identity the new microbiota-based intervention target for eggshell quality by exploring its underlying mechanisms. Our first specific aim is to determine whether changes in the microstructure associated with hens’ ageing are responsible for the observed weakness of the eggshells, and further identify the signaling pathways that link the gut microbiome to organic matrix metabolism. The metabolic alteration of organic matrix in response to gut microbiome will be investigated in both in vivo and in vitro experiments. Moreover, we will explore the possible role of organic matrix, as a central regulatory node, in inflammation and biomineralization. The results will provide new insights into the genesis and formation of calcium carbonate during eggshell formation. The current study will contribute to clarifying the mechanisms linking the microbiome to eggshell mechanical properties. And further understanding of the mechanisms will cast light on develop effective microbial interventions.

蛋壳破损问题给家禽生产业和鸡蛋加工业带来巨大的经济损失。如何缓解或有效解决产蛋后期蛋壳品质下降，是保障蛋鸡产业健康稳定发展和提升蛋鸡养殖效益急需解决的重大产业问题。基于前期研究工作的积累，申请者提出蛋壳超微结构的变异可能是导致后期蛋壳破损的重要成因；而肠道菌群干预能够调控蛋壳的超微结构，即影响蛋壳的矿化，进一步改善蛋壳的力学特性，但其作用机制尚不明晰。本项目拟以蛋壳有机基质的多重调控作用和蛋壳矿化为切入点，解析肠道微生物—有机基质—蛋壳超微结构的变化关系，揭示肠道微生物调控蛋鸡输卵管壳腺部有机基质代谢的机理，明确有机基质调控蛋壳矿化过程中碳酸钙成核和物相的机理。预期可探明蛋壳力学特性及缺陷发生的生物矿化基础，确定肠道菌群作为蛋壳结构及力学特性调控突破口的核心菌群及其功能，最终阐明肠道微生物通过有机基质调控蛋壳超微结构的机理，为改善蛋壳品质这一重大产业问题提供理论依据和技术支撑。

由蛋壳力学特性下降导致的蛋壳破损给禽蛋产业带来巨大的经济损失，尤其是产蛋后期蛋壳力学特性的下降仍然是蛋壳品质调控研究中的难点和热点。前期研究表明，肠道菌群干预能够调控蛋壳超微结构，进一步改善蛋壳的力学特性，但其作用机理尚不清楚。项目首先观察了蛋壳力学特性、超微结构和化学组成的周龄性变化，比较分析了不同生理阶段子宫部炎性免疫状态和基质蛋白、肠道-输卵管微生物的组成和传递，验证了关键基质蛋白的矿化作用。进一步研究了肠道微生物干预对子宫免疫反应、肠道屏障和蛋壳结构的影响和机理，以及输卵管微生物的功能。结果表明，65至80周龄蛋壳强度较31周龄下降20%以上，超微结构异常变化加剧了后期力学特性下降，乳突层厚度及比例增加、有效层厚度及比例降低和异常乳突体是后期蛋壳的结构特征。通过转录组学分析和炎性诱导模型，揭示子宫免疫炎性反应干扰基质蛋白合成和钙离子转运导致超微结构异常变化，明确了产蛋后期蛋鸡子宫矿化环境以低pH值、高抑菌类基质蛋白为特征，以及关键基质蛋白对碳酸钙晶体的调节作用。通过解析产蛋后期子宫部微生物组成及肠道-输卵管微生物传递差异，发现产蛋后期肠道微生物对子宫部微生物区系的贡献降低，揭示肠道微生物干预主要通过肠道屏障-机体炎性的间接途径调控子宫炎性免疫状态，进而改善蛋壳结构和力学特性的机理。此外，结果提示子宫微生物参与调控上皮细胞周期和细胞凋亡，其中，放线菌门（红球菌）、变形菌门（代尔夫特菌、寡养单胞菌、不动杆菌）、梭杆菌门（梭杆菌）与蛋壳品质密切相关。上述研究确定了产蛋后期蛋壳力学特性下降的主要结构特征，揭示了子宫免疫炎性反应干扰基质蛋白合成和钙离子转运导致超微结构异常，阐明了肠道微生物干预通过子宫炎性免疫状态调控蛋壳结构及力学特性的机理，可为改善产蛋后期蛋壳品质提供理论依据和技术支撑。

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