极端嗜酸热古菌Acidianus manzaensis硫氧化模型构建

Sulfur Oxidation Model Construction of Extremely Thermoacidophilic Archaea Acidianus manzaensis

为了解极端嗜酸热古菌硫氧化代谢途径,基于Acidianus manzaensis YN-25全基因组信息,通过NCBI数据库比对初步筛选了20个可能与硫氧化相关的基因,并通过实时定量PCR(RT-qPCR)比较了所筛选基因在以单质硫(S^0)和亚铁(Fe2+)两种不同能源底物培养下的表达差异。结果表明,A.manzaensis菌中存在至少15个与硫氧化相关的基因,经过比对分析,它们包括5个编码氧化单质硫(S^0)及含硫中间产物的酶基因、4个编码末端氧化酶基因、1个编码硫酸根转运蛋白酶基因、1个编码电子传递蛋白基因,以及4个编码与硫氧化密切相关的硫还原蛋白家族(Sulfur reduction protein)的dsr E基因。基于上述实验分析结果,拟构建极端嗜酸热古菌A.manzaensis的硫氧化模型,即胞外的S^0跨膜转运进入细胞内后,经硫氧化蛋白(SOR)氧化还原生成S_2O_3^(2-),SO_3^(2-)和H_2S等含硫中间产物。接着,细胞内通过其他相关硫氧化酶的作用将这些中间产物进一步氧化,并将氧化得到的电子传递给细胞膜上的氧化型醌(Q^(2+)),使其形成还原型的醌(QH_2),QH_2最终被末端氧化酶氧化形成NADH和ATP,从而为细胞生长提供能量。

To understand the metabolic pathway of sulfur oxidation in extremely thermoacidophilic archaea,20 possible genes related to sulfur oxidation were preliminarily screened by NCBI database alignment based on the complete genome sequence of Acidianus manzaensis YN-25. Quantitative real-time PCR（RT-qPCR）was used to analyze the differential expressions of the screened genes under two differentenergy substrates,elemental sulfur（S^0）and iron（Fe^2＋）. The results indicated that 15 genes were associated with sulfur oxidation from thecompartive analysis of the experiment results,including 5 genes encoding the enzymes of oxidizing S^0 and sulfur-containing intermediates,4 genes encoding terminal oxidase,1 gene encoding sulfate transporter permease,1 gene encoding electron transfer protein,and 4 dsr E genesencoding sulfur reduction protein family closely related to sulfur oxidation. Based on the above result of analysis,a sulfur oxidation model ofA. manzaensis was presented as below. Extracellular S^0 was transported into the cell through membrane,and reduced by sulfur oxygenasereductase（SOR）to be intermediates such as S2 O3^2-,SO3^2-and H2 S. Following,these sulfur-containing intermediates were further oxidizedby relevant enzymes inside cells,and the electrons from the oxidation were transferred to oxidized quinone（Q^2＋）on the cell membrane,fromwhich the reduced quinone（QH2）was formed. QH2 were eventually oxidized by terminal oxidase to be NADH and ATP providing energy for the growth of cells.