Ohta N, Ninfa A J, Allaire A, Kulick L, Newton A
Department of Molecular Biology, Princeton University, New Jersey 08544, USA.
J Bacteriol. 1997 Apr;179(7):2169-80. doi: 10.1128/jb.179.7.2169-2180.1997.
We report a detailed characterization of cell division cycle (cdc) genes in the differentiating gram-negative bacterium Caulobacter crescentus. A large set of temperature-sensitive cdc mutations was isolated after treatment with the chemical mutagen N-methyl-N'-nitro-N-nitrosoguanidine. Analysis of independently isolated mutants at the nonpermissive temperature identified a variety of well-defined terminal phenotypes, including long filamentous cells blocked at various stages of the cell division cycle and two unusual classes of mutants with defects in both cell growth and division. The latter strains are uniformly arrested as either short bagel-shaped coils or large predivisional cells. The polar morphology of these cdc mutants supports the hypothesis that normal cell cycle progression is directly responsible for developmental regulation in C. crescentus. Genetic and physical mapping of the conditional cdc mutations and the previously characterized dna and div mutations identified at least 21 genes that are required for normal cell cycle progression. Although most of these genes are widely scattered, the genetically linked divA, divB, and divE genes were shown by genetic complementation and physical mapping to be organized in one gene cluster at 3200 units on the chromosome. DNA sequence analysis and marker rescue experiments demonstrated that divE is the C. crescentus ftsA homolog and that the ftsZ gene maps immediately adjacent to ftsA. On the basis of these results, we suggest that the C. crescentus divA-divB-divE(ftsA)-ftsZ gene cluster corresponds to the 2-min fts gene cluster of Escherichia coli.
我们报道了对革兰氏阴性细菌新月柄杆菌分化过程中细胞分裂周期（cdc）基因的详细表征。在用化学诱变剂N-甲基-N'-硝基-N-亚硝基胍处理后，分离出了一大组温度敏感型cdc突变体。在非允许温度下对独立分离的突变体进行分析，确定了各种明确的终末表型，包括在细胞分裂周期不同阶段受阻的长丝状细胞，以及两类在细胞生长和分裂方面均有缺陷的异常突变体。后一类菌株均停滞为短的百吉饼状螺旋体或大的前分裂细胞。这些cdc突变体的极性形态支持了这样一种假说，即正常的细胞周期进程直接负责新月柄杆菌的发育调控。对条件性cdc突变以及先前表征的dna和div突变进行遗传和物理图谱分析，确定了至少21个正常细胞周期进程所需的基因。尽管这些基因大多广泛分散，但通过遗传互补和物理图谱分析表明，遗传连锁的divA、divB和divE基因在染色体上3200单位处组织成一个基因簇。DNA序列分析和标记拯救实验表明，divE是新月柄杆菌ftsA的同源物，ftsZ基因紧邻ftsA定位。基于这些结果，我们认为新月柄杆菌的divA-divB-divE（ftsA）-ftsZ基因簇对应于大肠杆菌的2分钟fts基因簇。
