Prakash L, Strauss B
J Bacteriol. 1970 Jun;102(3):760-6. doi: 10.1128/jb.102.3.760-766.1970.
Bacillus subtilis was not inactivated and was able to replicate even though approximately 3 x 10(4) methyl groups added by methyl methanesulfonate (MMS) were bound to the deoxyribonucleic acid (DNA) of each organism. No significant loss of methyl groups from the DNA occurred for several generations upon incubation of methylated wild-type or MMS-sensitive cells. Single-strand breaks were not observed in the DNA from cells treated at this low MMS dose. Higher doses of MMS resulted in significant killing of both wild-type and MMS-sensitive strains, and the DNA extracted from such treated cells sedimented more slowly than control DNA through alkaline sucrose gradients, indicating the presence of breaks or apurinic sites (or both). These breaks were repaired upon incubation of wild-type but not of MMS-sensitive strains. Repair of damage induced by alkylating agents is probably the repair of breaks which occur as a consequence of high levels of alkylation.
尽管甲磺酸甲酯（MMS）给每个生物体的脱氧核糖核酸（DNA）添加了约3×10⁴个甲基基团，但枯草芽孢杆菌并未被灭活，仍能够进行复制。甲基化的野生型或对MMS敏感的细胞在培养几代后，DNA上的甲基基团没有明显损失。在这种低MMS剂量处理的细胞的DNA中未观察到单链断裂。更高剂量的MMS导致野生型和MMS敏感菌株均大量死亡，并且从这种处理过的细胞中提取的DNA在碱性蔗糖梯度中比对照DNA沉降得更慢，表明存在断裂或脱嘌呤位点（或两者都有）。野生型菌株在培养后这些断裂得到修复，而MMS敏感菌株则没有。烷基化剂诱导的损伤修复可能是对由于高水平烷基化而产生的断裂的修复。
