Hadden C T
J Bacteriol. 1976 Oct;128(1):317-24. doi: 10.1128/jb.128.1.317-324.1976.
A mutant (uvr-1) of Bacillus subtilis that is deficient in excision of ultraviolet (UV)-induced pyrimidine dimers from deoxyribonucleic acid (DNA) shows a marked increase in ability to survive UV irradiation when plated on amino acid-supplemented agar medium compared with its survival ability when plated on nutrient plating medium, the effect is considered to be one of growth-dependent lethality. Irradiated stationary phase uvr-1 cells, incubated in liquid medium lacking amino acids required for growth, recover from this sensitivity to rich medium within 3 to 4 h after irradiation. Recovery is greatly reduced in the absence of glucose oiminated. Exponentially growing cells have a limited ability to recover from sensitivity to rich medium. Growth-dependent lethality can also occur in liquid medium. In nutrient broth the ability of irradiated stationary-phase uvr-1 cells to form colonies on defined agar medium decreases during postirradiation incubation, but treatmeth with chloramphenicol inhibits the loss of colony-forming ability. Recovery from sensitivity to rich media is inhibited by caffeine but not by 6-(p-hydroxyphenylazo)-uracil, and inhibitor of DNA replication. Alkaline sucrose gradient profiles show that conditions allowing recovery also favor maintaining intact DNA strands, whereas DNA strand breakage or degradation is associated with loss of viability. Recovery from sensitivity to rich medium has not been observed in the Ur+ parent or in strains carrying the mutations uvs-42 (another deficiency in dimer excision), recA1, or polA59. A uvr-1 recA1 mutants shows a higher level of recovery than does the recA1 single mutant, but a much lower level than the uvr-1 single mutant. Apparently, both the uvr-1 defect and Rec+ and PoII+ functions are essential for recovery from sensitivity to rich medium. For optimal recovery, growth immediately after irradiation must be delayed. The process requires energy, apparently involves recombination, and probably results in rejoining of DNA strands in which incision but not excision has occurred.
枯草芽孢杆菌的一种突变体（uvr - 1），其从脱氧核糖核酸（DNA）中切除紫外线（UV）诱导的嘧啶二聚体的能力存在缺陷。与接种在营养平板培养基上的存活能力相比，当接种在补充了氨基酸的琼脂培养基上时，该突变体在紫外线照射下的存活能力显著提高，这种效应被认为是生长依赖性致死效应之一。处于静止期的uvr - 1细胞经紫外线照射后，在缺乏生长所需氨基酸的液体培养基中培养，照射后3至4小时内可从这种对丰富培养基的敏感性中恢复。在没有葡萄糖的情况下，恢复能力会大大降低。指数生长期的细胞从对丰富培养基的敏感性中恢复的能力有限。生长依赖性致死效应也可在液体培养基中发生。在营养肉汤中，经紫外线照射的静止期uvr - 1细胞在照射后培养期间在限定琼脂培养基上形成菌落的能力会下降，但用氯霉素处理可抑制菌落形成能力的丧失。咖啡因可抑制从对丰富培养基的敏感性中恢复，而DNA复制抑制剂6 -（对羟基苯偶氮）尿嘧啶则无此作用。碱性蔗糖梯度分析表明，允许恢复的条件也有利于维持完整的DNA链，而DNA链的断裂或降解与活力丧失相关。在野生型Ur + 亲本或携带uvs - 42（另一种二聚体切除缺陷）、recA1或polA59突变的菌株中，未观察到从对丰富培养基的敏感性中恢复的现象。uvr - 1 recA1双突变体显示出比recA1单突变体更高水平的恢复，但比uvr - 1单突变体低得多。显然，uvr - 1缺陷以及Rec + 和PolII + 功能对于从对丰富培养基的敏感性中恢复都是必不可少的。为了实现最佳恢复效果，照射后必须延迟立即生长。该过程需要能量，显然涉及重组，并且可能导致已发生切口但未发生切除的DNA链重新连接。
