Li Xiaodan, Li Zhuofan, Li Ming, Li Jingwen, Wang Quan, Wang Shuxiang, Li Shuna, Li Hongya
College of Life Sciences, Hebei Agricultural University, Baoding, China.
Hebei Forage Microbial Technology Innovation Center, Baoding, Hebei, China.
Front Microbiol. 2024 Jan 25;15:1224855. doi: 10.3389/fmicb.2024.1224855. eCollection 2024.
Ligninolytic bacteria can secrete extracellular enzymes to depolymerize lignin into small-molecular aromatics that are subsequently metabolized and funneled into the TCA cycle. Carbohydrates, which are the preferred carbon sources of bacteria, influence the metabolism of lignin-derived aromatics through bacteria.
In this study, untargeted metabolomics and transcriptomics analyses were performed to investigate the effect of carbohydrates on lignin degradation mediated by MN-13, a strain with lignin-degrading activity that was isolated in our previous work.
The results demonstrated that the cell growth of the MN-13 strain and lignin removal were promoted when carbohydrates such as glucose and sodium carboxymethyl cellulose were added to an alkaline lignin-minimal salt medium (AL-MSM) culture. Metabolomics analysis showed that lignin depolymerization took place outside the cells, and the addition of glucose regulated the uptake and metabolism of lignin-derived monomers and activated the downstream metabolism process in cells. In the transcriptomics analysis, 299 DEGs were screened after 24 h of inoculation in AL-MSM with free glucose and 2 g/L glucose, respectively, accounting for 8.3% of the total amount of annotated genes. These DEGs were primarily assigned to 30 subcategories, including flagellar assembly, the PTS system, RNA degradation, glycolysis/gluconeogenesis, the TCA cycle, pyruvate metabolism, and tryptophan metabolism. These subcategories were closely associated with the cell structure, generation of cellular energy, and precursors for biosynthetic pathways, based on a - log (P adjust) value in the KEGG pathway analysis.
In summary, the addition of glucose increased lignin degradation mediated by the MN-13 strain through regulating glycolysis, TCA cycle, and central carbon metabolism.
木质素分解细菌可分泌细胞外酶，将木质素解聚为小分子芳烃，这些小分子芳烃随后被代谢并进入三羧酸循环。碳水化合物是细菌的首选碳源，它通过细菌影响木质素衍生芳烃的代谢。
在本研究中，进行了非靶向代谢组学和转录组学分析，以研究碳水化合物对MN-13介导的木质素降解的影响。MN-13是我们之前工作中分离出的具有木质素降解活性的菌株。
结果表明，在碱性木质素-基本盐培养基（AL-MSM）培养中添加葡萄糖和羧甲基纤维素钠等碳水化合物时，MN-13菌株的细胞生长和木质素去除得到促进。代谢组学分析表明，木质素解聚发生在细胞外，葡萄糖的添加调节了木质素衍生单体的摄取和代谢，并激活了细胞内的下游代谢过程。在转录组学分析中，分别在含有游离葡萄糖和2 g/L葡萄糖的AL-MSM中接种24小时后筛选出299个差异表达基因（DEG），占注释基因总数的8.3%。这些DEG主要分为30个亚类，包括鞭毛组装、磷酸转移酶系统、RNA降解、糖酵解/糖异生、三羧酸循环、丙酮酸代谢和色氨酸代谢。基于KEGG通路分析中的-log（P调整）值，这些亚类与细胞结构、细胞能量产生和生物合成途径的前体密切相关。
总之，添加葡萄糖通过调节糖酵解、三羧酸循环和中心碳代谢增加了MN-13菌株介导的木质素降解。
