HoLMiR-Hohenheim Center for Livestock Microbiome Research, University of Hohenheim, 70599 Stuttgart, Germany.
Institute of Animal Science, University of Hohenheim, 70599 Stuttgart, Germany.
Int J Mol Sci. 2021 Sep 22;22(19):10202. doi: 10.3390/ijms221910202.
Monensin is an ionophore for monovalent cations, which is frequently used to prevent ketosis and to enhance performance in dairy cows. Studies have shown the rumen bacteria B4 being less affected by monensin. The present study aimed to reveal more information about the respective molecular mechanisms in , as there is still a lack of knowledge about defense mechanisms against monensin. Cell growth experiments applying increasing concentrations of monensin and incubations up to 72 h were done. Harvested cells were used for label-free quantitative proteomics, enzyme activity measurements, quantification of intracellular sodium and extracellular glucose concentrations and fluorescence microscopy. Our findings confirmed an active cell growth and fermentation activity of B4 despite monensin concentrations up to 60 µM. An elevated abundance and activity of the Na-translocating NADH:quinone oxidoreductase counteracted sodium influx caused by monensin. Cell membranes and extracellular polysaccharides were highly influenced by monensin indicated by a reduced number of outer membrane proteins, an increased number of certain glucoside hydrolases and an elevated concentration of extracellular glucose. Thus, a reconstruction of extracellular polysaccharides in in response to monensin is proposed, which is expected to have a negative impact on the substrate binding capacities of this rumen bacterium.
莫能菌素是一种单价阳离子载体，常用于预防奶牛酮病和提高奶牛生产性能。研究表明，莫能菌素对瘤胃细菌 B4 的影响较小。本研究旨在更深入地了解其各自的分子机制，因为目前对于该细菌防御莫能菌素的机制仍知之甚少。通过添加不同浓度的莫能菌素并孵育长达 72 小时，进行了细胞生长实验。收集细胞用于无标记定量蛋白质组学、酶活性测量、细胞内钠离子和细胞外葡萄糖浓度的定量以及荧光显微镜检测。我们的研究结果证实了尽管存在高达 60µM 的莫能菌素，B4 仍具有活跃的细胞生长和发酵活性。Na 转运 NADH：醌氧化还原酶的丰度和活性升高，抵消了莫能菌素引起的钠离子内流。细胞膜和细胞外多糖受到莫能菌素的强烈影响，表现为外膜蛋白数量减少、某些糖苷水解酶数量增加以及细胞外葡萄糖浓度升高。因此，提出了 B4 响应莫能菌素而重建细胞外多糖的假设，这预计会对该瘤胃细菌的底物结合能力产生负面影响。
