COMPLETION OF REPLICATION AND DIVISION CYCLE IN TEMPERATURE-SENSITIVE DNA INITIATION MUTANTS OF BACILLUS-SUBTILIS-168 AT NON-PERMISSIVE TEMPERATURE
COMPLETION OF REPLICATION AND DIVISION CYCLE IN TEMPERATURE-SENSITIVE DNA INITIATION MUTANTS OF BACILLUS-SUBTILIS-168 AT NON-PERMISSIVE TEMPERATURE
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DOI：
10.1016/0022-2836(77)90023-7
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发表时间：
1977-01-01
影响因子：
5.6
通讯作者：
WAKE, RG
中科院分区：
文献类型：
--
作者：
CALLISTER, H;WAKE, RG
使枯草芽孢杆菌168、TsB134和dna-1(Ts)的温度敏感DNA起始突变体的孢子在34°C下萌发。 C在[3H]胸腺嘧啶存在下直至第一轮复制开始后。然后，[3H]胸腺嘧啶被非放射性胸腺嘧啶取代，并将生长的孢子转移到更高的温度（TsB134为49°C，dna-1(Ts)为45°C），这完全阻止了第二轮复制的启动。在这种条件下形成的菌落的放射自显影显示大多数含有2个颗粒簇。在大多数情况下，簇被分隔隔膜分开。因此，在每种情况下，DNA基因产物的温度敏感性活性显然对于通过染色体终止区的复制或随后的子代分离来说是不需要的。对隔膜过程的进一步研究表明，当发芽后第一轮的复制在不允许的温度下继续终止时，两个突变体中很容易出现位于中心的隔膜。在实验时间内阻止一轮进展至终止的胸腺嘧啶水平下，在相同长度的集落中不发生中央分隔。相反，不对称分隔发生的频率相对较低。显然，中央隔膜的形成与终止有关，反映了非允许温度下的正常分裂分隔。在这两种突变体中，这种分隔都不需要温度敏感的 DNA 基因产物在整个循环的后期发挥作用。
Spores of the temperature-sensitive DNA initiation mutants of B. subtilis 168, TsB134 and dna-1(Ts), were allowed to germinate at 34.degree. C in the presence of [3H]thymine until after the start of the 1st round of replication. The [3H]thymine was then replaced by non-radioactive thymine and the outgrowing spores transferred to a higher temperature (49.degree. C for TsB134, 45.degree. C for dna-1(Ts)) which blocked completely the initiation of a 2nd round of replication. Autoradiography of the colonies which developed under such conditions showed the majority to contain 2 grain clusters. In most cases the clusters were separated by a division septum. Thus, the temperature-sensitive activity of the dna gene product in each case is apparently not needed for replication through the termination region of the chromosome or the ensuing segregation of the daughters. Further studies of the septation process showed that, when replication of the 1st round after germination was allowed to proceed to termination at the non-permissive temperature, a centrally located septum appeared readily in both mutants. At levels of thymine which prevented progress of the round to termination within the time of the experiment, central septation did not occur in colonies of the same length. Rather, asymmetrical septation occurred at a relatively low frequency. Apparently, the formation of the central septum is coupled to termination and reflects normal division septation at the non-permissive temperature. In neither mutant does such septation require the action of the temperature-sensitive dna gene product at a late stage in the overall cycle.