Pfeifer F, Blaseio U, Horne M
Max-Planck-Institut für Biochemie, Martinsried, Federal Republic of Germany.
Can J Microbiol. 1989 Jan;35(1):96-100. doi: 10.1139/m89-015.
Halobacterium halobium contains two gas vacuole protein genes that are located in plasmid pHH1 (p-vac) and in the chromosomal DNA (c-vac). The mutation frequency for these genes is different: the constitutively expressed p-vac gene is mutated with a frequency of 10(-2), while the chromosomal gene expressed in the stationary phase of growth is mutated with a frequency of 10(-5). The difference in the mutation susceptibility is due to the dynamics of plasmid pHH1. p-vac gene mutations are caused (i) by the integration of an insertion element or (ii) by a deletion event encompassing the p-vac gene region. In contrast, c-vac mutants analyzed to date incurred neither insertion elements nor deletions. Deletion events within pHH1 occur at high frequencies during the development of a H. halobium culture. The investigation of the fusion regions resulting from deletion events indicates that insertion elements are involved. The analysis of pHH1 deletion variants led to a 4 kilobase pair DNA region containing the origin of replication of the pHH1 plasmid.
嗜盐栖热菌含有两个气胞蛋白基因，分别位于质粒pHH1（p-vac）和染色体DNA（c-vac）中。这些基因的突变频率不同：组成型表达的p-vac基因的突变频率为10^(-2)，而在生长稳定期表达的染色体基因的突变频率为10^(-5)。突变敏感性的差异是由于质粒pHH1的动态变化。p-vac基因突变是由（i）插入元件的整合或（ii）包含p-vac基因区域的缺失事件引起的。相比之下，迄今为止分析的c-vac突变体既没有插入元件也没有缺失。在嗜盐栖热菌培养物的发育过程中，pHH1内的缺失事件高频发生。对缺失事件产生的融合区域的研究表明插入元件参与其中。对pHH1缺失变体的分析导致了一个包含pHH1质粒复制起点的4千碱基对DNA区域。
