Characterization of dissimilatory Fe(III) versus NO3- reduction in the hyperthermophilic archaeon Pyrobaculum aerophilum
Characterization of dissimilatory Fe(III) versus NO3- reduction in the hyperthermophilic archaeon Pyrobaculum aerophilum
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DOI：
10.1128/jb.188.2.525-531.2006
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发表时间：
2006-01-01
影响因子：
3.2
通讯作者：
Holden, JF
中科院分区：
文献类型：
--
作者：
Feinberg, LF;Holden, JF
嗜热古细菌嗜气焦杆菌（Pyrobaculum aerophilum）以20 mM的柠檬酸铁（III）、100 mM的低结晶铁（III）氧化物和10 mM的KNO3作为终端电子受体。两种形式的铁以不同的速率还原，但生长产量相等。不溶性铁通过透析管在空间上分离后减少，表明与铁的直接接触不是生长所必需的。当分离时，生长后管子外没有检测到铁（III）或铁（II），这表明电子穿梭而不是螯合剂可能被用作铁还原的细胞外介质。在新鲜培养基中添加25%和50% （vol vol(-1)）无细胞的废不溶性铁培养基，导致生长无滞后期。废培养基的液相色谱分析表明，培养在铁中，特别是不溶性铁中，产生可溶性的细胞外化合物，而这些化合物在废硝酸盐培养基中不存在或含量较少。与硝酸盐培养的细胞相比，铁培养细胞的全细胞提取物中nadh依赖性铁还原酶活性增加了约100倍，而硝酸盐还原酶活性降低了10倍，这表明异化铁还原受到调节。一种新的2,6-蒽醌二磺酸氧化酶活性在铁培养的细胞中比在硝酸盐培养的细胞中高580倍以上。该活性主要（> 95%）与膜细胞部分有关，但其生理功能尚不清楚。硝酸盐培养产生两种膜结合的c型细胞色素，通过基因组分析预测它们是单血红素和亚硝酸盐还原酶的一部分，以及一个be复合物。在柠檬酸铁上生长的细胞中，只有一种细胞色素存在，其相对丰度不变。
The hyperthermophilic archaeon Pyrobaculum aerophilum used 20 mM Fe(III) citrate, 100 mM poorly crystalline Fe(III) oxide, and 10 mM KNO3 as terminal electron acceptors. The two forms of iron were reduced at different rates but with equal growth yields. The insoluble iron was reduced when segregated spatially by dialysis tubing, indicating that direct contact with the iron was not necessary for growth. When partitioned, there was no detectable Fe(III) or Fe(II) outside of the tubing after growth, suggesting that an electron shuttle, not a chelator, may be used as an extracellular mediator of iron reduction. The addition of 25 and 50% (vol vol(-1)) cell-free spent insoluble iron media to fresh media led to growth without a lag phase. Liquid chromatography analysis of spent media showed that cultures grown in iron, especially insoluble iron, produced soluble extracellular compounds that were absent or less abundant in spent nitrate medium. NADH-dependent ferric reductase activity increased approximately 100-fold, while nitrate reductase activity decreased 10-fold in whole-cell extracts from iron-grown cells relative to those from nitrate-grown cells, suggesting that dissimilatory iron reduction was regulated. A novel 2,6-anthrahydroquinone disulfonate oxidase activity was more than 580-fold higher in iron-grown cells than in nitrate-grown cells. The activity was primarily (> 95%) associated with the membrane cellular fraction, but its physiological function is unknown. Nitrate-grown cultures produced two membrane-bound, c-type cytochromes that are predicted to be monoheme and part of nitrite reductase and a be, complex using genome analyses. Only one cytochrome was present in cells grown on Fe(III) citrate whose relative abundance was unchanged.