Levels of oxidized and reduced pyridine nucleotides in dormant spores and during growth, sporulation, and spore germination of Bacillus megaterium
Levels of oxidized and reduced pyridine nucleotides in dormant spores and during growth, sporulation, and spore germination of Bacillus megaterium
复制标题
巨大芽孢杆菌休眠孢子中以及生长、孢子形成和孢子萌发过程中氧化和还原吡啶核苷酸的水平
作者：
B. Setlow;P. Setlow
巨大芽孢杆菌的休眠孢子不含可检测到的还原型烟酰胺腺嘌呤二核苷酸 (NADH) 或还原型烟酰胺腺嘌呤二核苷酸磷酸 (NADPH)，尽管这些核苷酸的氧化形式（NAD 和 NADP）含量很高。在孢子萌发的最初几分钟内，NADH 和 NADPH 迅速积累。然而，这种积累是随着光密度下降而发生的，而光密度是孢子萌发起始的特征。发芽早期NADH和NADPH的积累不受氟化物或氰化物的阻碍，甚至在没有外源还原力的情况下进行发芽时也会发生。除了吡啶核苷酸减少之外，随着吡啶核苷酸水平增加到生长细胞中发现的水平，从头合成也在发芽早期开始。在几种不同培养基中生长的对数中期细胞的吡啶核苷酸总量是休眠孢子的 20 至 35 倍。然而，随着生长和孢子形成的进行，NADH 加 NAD 水平下降了四到五倍，而 NADPH 加 NADP 水平下降幅度较小。从孢子萌发第 10 分钟到孢子形成中期，NADH/NAD 的比率值约为 0.1（0.03 至 0.18），而 NADPH/ANDP 的比率值约为 1.4（0.3 至 2.4）。对所有三种测试的生长介质中对数期与静止期（孢子形成）生长的这些比率进行比较，没有揭示任何常见的变化模式。
Dormant spores of Bacillus megaterium contained no detectable reduced nicotinamide adenine dinucleotide (NADH) or reduced nicotinamide adenine dinucleotide phosphate (NADPH) despite significant levels of the oxidized forms of these nucleotides (NAD and NADP). During the first minutes of spore germination there was rapid accumulation of NADH and NADPH. However, this accumulation followed the fall in optical density that is characteristic of the initiation of spore germination. Accumulation of NADH and NADPH early in germination was not blocked by fluoride or cyanide, and it occurred even when germination was carried out in the absence of an exogenous source of reducing power. In addition to pyridine nucleotide reduction, de novo synthesis also began early in germination as the pyridine nucleotide levels increased to those found in growing cells. Midlog-phase cells grown in several different media had 20 to 35 times as much total pyridine nucleotide as did dormant spores. However, as growth and sporulation proceeded, the NADH plus NAD level fell four- to fivefold whereas the NADPH plus NADP level fell by a lesser amount. From min 10 of spore germination until midway through sporulation the value for the ratio of NADH/NAD is about 0.1 (0.03 to 0.18) while the ratio of NADPH/ANDP is about 1.4 (0.3 to 2.4). Comparison of these ratios in log-phase versus stationary phase (sporulation) growth in all three growth media tested did not reveal any common pattern of changes.