Lipopolysaccharides (LPS) are outer membrane components of Gram-negative bacteria made of three regions: the O-antigen; the core oligosaccharide; and a glucosamine disaccharide linked to hydroxy fatty acids, which is named lipid A. The number phosphate groups, and hydroxy fatty acid chains is associated with the immunopotency and the immunomodulatory activity of LPS, where six-acyl chain lipid A with two phosphate groups is found in virulent strains and five- or four-acyl chain lipid A with one phosphate group are found in non-virulent bacteria strains. Ruminal bacteria are predominantly Gram-negative and their LPS have not been thoroughly investigated. In the rumen, LPS is comprised of mixed ruminal LPS. Drawing upon a body of theoretical and applied work, this paper aims to critically review the scientific literature regarding single-species and mixed ruminal bacteria LPS, highlighting the importance of ruminal LPS to the host. Lastly, future research directions are suggested in order to further our understanding of the roles of LPS in the rumen. Possible suggestions for further understanding ruminal LPS include (1) in silico evaluation of major bacteria contributing to ruminal LPS, (2) structural characterization of LPS from prominent ruminal bacteria species, such as ruminal selenomonads and Megasphaera elsdenii, and, (3) ruminal epithelial tissue immune response evaluation from single-species and mixed ruminal LPS. In conclusion, this review identifies numerous areas for future research, including setting the basis for future modeling and simulation of host microbiome interactions in ruminants.

中文翻译：

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瘤胃细菌脂多糖：免疫学和微生物学展望

脂多糖 (LPS) 是革兰氏阴性菌的外膜成分，由三个区域组成：O 抗原；核心寡糖；和与羟基脂肪酸相连的氨基葡萄糖二糖，称为脂质A。磷酸基团的数量和羟基脂肪酸链与LPS的免疫能力和免疫调节活性有关，其中具有两个磷酸基团的六酰基链脂质A是在毒性菌株中发现，在非毒性菌株中发现带有一个磷酸基团的五或四酰基链脂质A。瘤胃细菌主要是革兰氏阴性菌，它们的 LPS 尚未得到彻底研究。在瘤胃中，LPS 由混合瘤胃 LPS 组成。借鉴大量理论和应用工作，本文旨在批判性地回顾有关单种和混合瘤胃细菌LPS的科学文献，突出瘤胃LPS对宿主的重要性。最后，提出了未来的研究方向，以进一步了解 LPS 在瘤胃中的作用。进一步了解瘤胃 LPS 的可能建议包括 (1) 计算机评估促成瘤胃 LPS 的主要细菌，(2) 来自突出瘤胃细菌种类的 LPS 的结构表征，例如瘤胃硒单胞菌和 Megasphaera elsdenii，以及 (3) 瘤胃上皮来自单一物种和混合瘤胃LPS的组织免疫反应评价。总之，本综述确定了未来研究的许多领域，包括为未来反刍动物宿主微生物组相互作用的建模和模拟奠定基础。