图1 天然甲酸利用微生物CBB cycle—Calvin-Benson-Bassham循环；THF—四氢叶酸；THMPT—四氢甲基蝶呤

Fig. 1 Natural formate-utilizing microorganismsCBB cycle—Calvin-Benson-Bassham cycle; THF—tetrahydrofolate; THMPT—tetrahydromethanopterin

图2 代谢工程改造的微生物P AOX1 —醇氧化酶启动子；THF—四氢叶酸

Fig. 2 Metabolically engineered microorganismsP AOX1 —alcohol oxidase 1 promoter; THF—tetrahydrofolate

图3 天然甲酸利用路径（绿色底色的化合物为路径底物，粉色底色的化合物为路径产物）Ack—乙酸激酶；Acs—乙酰辅酶A合成酶；COdh—CO脱氢酶；CoFeSP—钴铁硫蛋白；Eno—烯醇化酶；Fch—次甲基四氢叶酸环水解酶；Fdh—甲酸脱氢酶；Ftl—甲酸四氢叶酸连接酶；Fts—甲酰四氢叶酸合成酶；Gapdh—3-磷酸甘油醛脱氢酶；GCS—甘氨酸裂解系统；Gk—甘油酸激酶；GlyA—丝氨酸羟甲基转移酶；GR—甘氨酸还原酶复合体；Hpr—羟基丙酮还原酶；Madh—苹果酸脱氢酶；Mcl—苹果酰辅酶A裂解酶；Metr—甲基转移酶；Mtd—亚甲基四氢叶酸脱氢酶；Mtk—苹果酸裂解酶；Mtr—亚甲基四氢叶酸还原酶；PFOR—丙酮酸铁氧还蛋白氧化还原酶；Pgk—磷酸甘油酸激酶；Ppc—PEP羧化酶；Prk—磷酸核酮糖激酶；Rubisco—核酮糖-1，5-二磷酸羧化酶/加氧酶；Sda—丝氨酸脱氨酶；Sgt—丝氨酸-乙醛酸转氨酶；THF—四氢叶酸

Fig. 3 Natural formate-utilizing pathways(compounds with a green background are pathway substrates; compounds with a pink background are pathway products) Ack—Acetate kinase; Acs—acetyl-CoA synthase; COdh—CO dehydrogenase; CoFeSP—corrinoid ironsulfur protein; Eno—enolase; Fch—methenyl-tetrahydrofolate cyclohydrolase; Fdh—formate dehydrogenase; Ftl—formate-tetrahydrofolate ligase; Fts—formyl-tetrahydrofolate synthetase; Gapdh—glyceraldehyde-3-phosphate dehydrogenase; GCS—glycine cleavage system; Gk—glycerate kinase; GlyA—serine hydroxymethyltransferase; GR—Glycine reductase complex; Hpr—hydroxypyruvate reductase; Madh—malate dehydrogenase; Mcl—malyl-CoA lyase; Metr—methyltransferase; Mtd—methylene-tetrahydrofolate dehydrogenase; Mtk—malate thiokinase; Mtr—methylene-tetrahydrofolate reductase; PFOR—Pyruvate ferredoxin oxidoreductase; Pgk—Phosphoglycerate kinase; Ppc—phosphoenolpyruvate carboxylase; Prk—phosphoribulo kinase; Rubisco—Ribulose-1,5-bisphosphate carboxylase/oxygenase; Sda—serine deaminase; Sgt—serine-glyoxylate transaminase; THF—tetrahydrofolate

图4 重构优化甲酸利用路径（绿色底色的化合物为路径底物，粉色底色的化合物为路径产物）Acdh—乙醛脱氢酶；Acs—乙酰辅酶A合成酶；Agt—丙氨酸-乙醛酸转氨酶；CA—碳酸酐酶；Faldh—甲醛脱氢酶；Fch—次甲基四氢叶酸环水解酶；Fdh—甲酸脱氢酶；Fthfl—甲酸四氢叶酸连接酶；Ftl—甲酸四氢叶酸连接酶；GCS—甘氨酸裂解系统；Gldh—谷氨酸脱氢酶；GlyA—丝氨酸羟甲基转移酶；Gpt—谷氨酸-丙酮酸转氨酶；Hal—HOB醛缩酶；Hat—HOB转氨酶；Hsk—高丝氨酸激酶；Lta—苏氨酸醛缩酶；Madh—苹果酸脱氢酶；Mcl—苹果酰辅酶A裂解酶；Medh—甲醇脱氢酶；Mtd—亚甲基四氢叶酸脱氢酶；Mthfs—5，10-亚甲基四氢叶酸合成酶；Mtk—苹果酸硫激酶；Oxidative PPP—氧化戊糖磷酸途径；Pfk—磷酸果糖激酶；Ppc—PEP羧化酶；Pps—PEP合成酶；Prk—磷酸核酮糖激酶；Rubisco—核酮糖-1，5-二磷酸羧化酶；Sal—丝氨酸醛缩酶；Sda—丝氨酸脱氨酶；THF—四氢叶酸；Ts—苏氨酸合成酶；Zwf—6-磷酸葡萄糖脱氢酶

Fig. 4 Reconstruction and optimization of formate-utilizing pathways(compounds with a green background are pathway substrates; compounds with a pink background are pathway products) Acdh—acetaldehyde dehydrogenase; Acs—acetyl-CoA synthase; Agt—alanine-glyoxylate transaminase; CA—carbonic anhydrase; Faldh—formaldehyde dehydrogenase; Fch—methenyl-tetrahydrofolate cyclohydrolase; Fdh—formate dehydrogenase; Fthfl—formate-tetrahydrofolate ligase; Ftl—formate-tetrahydrofolate ligase; GCS—glycine cleavage system; Gldh—glutamate dehydrogenase; GlyA—serine hydroxymethyltransferase; Gpt—glutamate-pyruvate transaminase; Hal—4-hydroxy-2-oxobutanoate aldolase; Hat—4-hydroxy-2-oxobutanoate aminotransferase; Hsk—homoserine kinase; Lta—threonine aldolase; Madh—malate dehydrogenase; Mcl—malyl-CoA lyase; Medh—methanol dehydrogenase; Mtd—methylene-tetrahydrofolate dehydrogenase; Mthfs—5,10-methylene-tetrahydrofolate synthase; Mtk—malate thiokinase; Oxidative PPP—Oxidative pentose-phosphate pathway; Pfk—phosphofructokinase; Ppc—phosphoenolpyruvate carboxylase; Pps—phosphoenolpyruvate synthase; Prk—phosphoribulo kinase; Rubisco—ribulose-1,5-bisphosphate carboxylase; Sal—serine aldolase; Sda—serine deaminase; THF—tetrahydrofolate; Ts—threonine synthase; Zwf—glucose-6-phosphate dehydrogenase

图5 人工设计甲酸利用路径Acdh—乙醛脱氢酶；Acs—乙酰辅酶A合成酶；Acps—乙酰磷酸合成酶；Dhak—二羟基丙酮激酶；Fls—甲醛酶；Gals—乙醇醛合成酶；Pta—磷酸转乙酰酶（绿色底色的化合物为路径底物，粉色底色的化合物为路径产物）

Fig. 5 Artificial formate-utilizing pathwaysAcdh—acetaldehyde dehydrogenase; Acs—acetyl-CoA synthase; Acps—acetyl phosphate synthase; Dhak—dihydroxyacetone kinase; Fls—formolase; Gals—glycolaldehyde synthase; Pta—phosphate acetyltransferase (compounds with a green background are pathway substrates, compounds with a pink background are pathway products)

图6 提高甲酸同化效率的关键方法FDH—甲酸脱氢酶；Hint—H蛋白的氨甲基化形式；Hox—H蛋白的氧化形式；Hred—H蛋白的还原形式；TCA cycle—三羧酸循环；THF—四氢叶酸

Fig. 6 Key methods to improve the efficiency of formate assimilationFDH—formate dehydrogenase; Hint—aminomethylated form of H protein; Hox—oxidized form of H protein; Hred—reduced form of H protein; TCA cycle—tricarboxylic acid cycle; THF—tetrahydrofolate;

图7 改善甲酸利用微生物细胞生长的关键方法

Fig. 7 Key methods to improve the cell growth of formate-utilizing microorganisms