School of Basic Medical Sciences and Forensic Medicine, Hangzhou Medical College, Hangzhou, 310059, PR China.
College of Biotechnology and Bioengineering, Zhejiang University of Technology, Hangzhou, 310032, PR China.
BMC Genomics. 2024 Oct 28;25(1):1008. doi: 10.1186/s12864-024-10923-w.
Methylobacterium sp. XJLW converts formaldehyde into methanol and formic acid via a Cannizzaro reaction in response to environmental formaldehyde stress. Methanol is further assimilated without formaldehyde or formic acid formation, whereas formic acid accumulates without undergoing further metabolism. Synthetic biology-based biotransformation of methanol to generate additional products can potentially achieve carbon neutrality. However, practical applications are hampered by limitations such as formaldehyde tolerance. In this study, we aimed to explore the specific mechanism of strain XJLW in response to formaldehyde stress. Thus, a transcriptomic analysis of XJLW under formaldehyde treatment was performed, revealing changes in the expression of specific genes related to one-carbon metabolism. Central metabolic genes were downregulated, whereas metabolic bypass genes were upregulated to maintain methanol assimilation in XJLW's response to formaldehyde treatment. In total, 100 genes potentially related to methyl transfer were identified. The function of only one gene, RS27765, was similar to that of glyA, which encodes a methyltransferase involved in one-carbon metabolism. The double-mutant strain, lacking RS27765 and glyA, lost its ability to grow in methanol, whereas the single-mutant strain, lacking only one of these genes, still grew in methanol. Co-expression of RS27765 and RS31205 (YscQ/HrcQ type III secretion apparatus protein) enabled Escherichia coli BL21 (DE3) to effectively degrade methanol. Using protein sequence analysis and molecular docking, we proposed a model wherein RS27765 is necessary for cell growth by using methanol generated via formaldehyde cannizzaro reaction. This process enables direct assimilation of methanol without producing formaldehyde and formic acid as intermediate metabolites. The RS27765 gene cluster, in conjunction with metabolic bypass genes, constitutes a novel auxiliary pathway facilitating formaldehyde stress tolerance in the strain.
甲基杆菌 XJLW 通过康尼扎罗反应将甲醛转化为甲醇和甲酸，以应对环境甲醛胁迫。甲醇进一步被同化，而没有甲醛或甲酸的形成，而甲酸则在没有进一步代谢的情况下积累。基于合成生物学的甲醇生物转化为产生额外产品可以潜在地实现碳中和。然而，实际应用受到甲醛耐受性等限制。在这项研究中，我们旨在探索菌株 XJLW 对甲醛胁迫的具体反应机制。因此，对 XJLW 在甲醛处理下的转录组进行了分析，揭示了与一碳代谢相关的特定基因表达的变化。中心代谢基因下调，而代谢旁路基因上调，以维持 XJLW 对甲醛处理的甲醇同化。总共鉴定出 100 个可能与甲基转移相关的基因。只有一个基因 RS27765 的功能与 glyA 相似，glyA 编码参与一碳代谢的甲基转移酶。缺乏 RS27765 和 glyA 的双突变株丧失了在甲醇中生长的能力，而仅缺失这些基因之一的单突变株仍能在甲醇中生长。RS27765 和 RS31205（YscQ/HrcQ 型 III 型分泌装置蛋白）的共表达使大肠杆菌 BL21（DE3）能够有效地降解甲醇。通过蛋白质序列分析和分子对接，我们提出了一个模型，其中 RS27765 通过使用甲醛康尼扎罗反应生成的甲醇来促进细胞生长。这个过程使得甲醇可以直接同化，而没有作为中间代谢物的甲醛和甲酸。RS27765 基因簇与代谢旁路基因一起构成了一种新的辅助途径，使该菌株能够耐受甲醛胁迫。
