Citric acid cycle in the hyperthermophilic archaeon Pyrobaculum islandicum grown autotrophically, heterotrophically, and mixotrophically with acetate
Citric acid cycle in the hyperthermophilic archaeon Pyrobaculum islandicum grown autotrophically, heterotrophically, and mixotrophically with acetate
复制标题
DOI：
10.1128/jb.00138-06
复制
发表时间：
2006-06-01
影响因子：
3.2
通讯作者：
Holden, James F.
中科院分区：
文献类型：
--
作者：
Hu, Yajing;Holden, James F.
超嗜热古菌Pyrobaculum islandicum使用的柠檬酸循环在氧化和还原方向的异养和自养生长，分别，但碳流的控制知之甚少。在95 ° C下，用乙酸盐、H-2和少量酵母提取物以及用硫代硫酸盐作为末端电子受体，使海岛假单胞菌以自养、异养和兼养方式生长。细胞的自养生长速率和最大浓度显著低于其他培养基。在H2和0.001%酵母提取物上，含和不含0.05%乙酸盐的生长速率相同，但细胞的最大浓度是含乙酸盐的四倍。如果不存在0.001%的酵母提取物，则没有乙酸盐的生长，并且向含乙酸盐的培养基中添加H2大大增加了细胞的生长速率和最大浓度。在H和酵母提取物存在下，P. islandicum培养物同化C-14标记的乙酸盐，效率为55%。在3种不同的生长条件下，参与海岛棉代谢的19种酶中有11种酶的活性受到了调控。丙酮酸合酶和乙酸：辅酶A（CoA）连接酶（ADP形成）的活动，只在异养生长的文化。柠檬酸合酶活性下降，在自养和含乙酸的文化相比，在异养文化的活动。乙酰化柠檬酸裂解酶，乙酸：CoA连接酶（AMP形成），磷酸烯醇式丙酮酸羧化酶的活动增加，在自养和含乙酸的文化。柠檬酸裂解酶活性高于ATP柠檬酸合成酶活性在自养培养。这些数据表明，柠檬酸裂解酶和AMP形成乙酸：CoA连接酶，但不是ATP柠檬酸合酶，相反的柠檬酸合酶的工作，以控制柠檬酸循环中的碳流的方向。
The hyperthermophilic archaeon Pyrobaculum islandicum uses the citric acid cycle in the oxidative and reductive directions for heterotrophic and autotrophic growth, respectively, but the control of carbon flow is poorly understood. P. islandicum was grown at 95 degrees C autotrophically, heterotrophically, and mixotrophically with acetate, H-2, and small amounts of yeast extract and with thiosulfate as the terminal electron acceptor. The autotrophic growth rates and maximum concentrations of cells were significantly lower than those in other media. The growth rates on H2 and 0.001% yeast extract with and without 0.05% acetate were the same, but the maximum concentration of cells was fourfold higher with acetate. There was no growth with acetate if 0.001% yeast extract was not present, and addition of H, to acetate-containing medium greatly increased the growth rates and maximum concentrations of cells. P. islandicum cultures assimilated C-14-labeled acetate in the presence of H, and yeast extract with an efficiency of 55%. The activities of 11 of 19 enzymes involved in the central metabolism of P. islandicum were regulated under the three different growth conditions. Pyruvate synthase and acetate:coenzyme A (CoA) ligase (ADP-forming) activities were detected only in heterotrophically grown cultures. Citrate synthase activity decreased in autotrophic and acetate-containing cultures compared to the activity in heterotrophic cultures. Acetylated citrate lyase, acetate:CoA ligase (AMP forming), and phosphoenolpyruvate carboxylase activities increased in autotrophic and acetate-containing cultures. Citrate lyase activity was higher than ATP citrate synthase activity in autotrophic cultures. These data suggest that citrate lyase and AMP-forming acetate:CoA ligase, but not ATP citrate synthase, work opposite citrate synthase to control the direction of carbon flow in the citric acid cycle.