Ginard M, Lalucat J, Tümmler B, Römling U
Department de Biologia Ambiental, Universitat de les Illes Balears, Palma de Mallorca, Spain.
Int J Syst Bacteriol. 1997 Jan;47(1):132-43. doi: 10.1099/00207713-47-1-132.
In order to determine the genome variability within Pseudomonas stutzeri, 20 strains representing the seven described genomovars and strain JM300 were analyzed by using various resolution levels of rare cutting enzymes. XbaI and SpeI fingerprints revealed a high degree of heterogeneity of restriction patterns that did not correlate with the division into genomovars. However, a fragment pattern comparison led to the establishment of several groups of clonal variants within genomovars. One circular chromosome ranging in size from 3.75 to 4.64 Mb constitutes the genome of P. stutzeri strains. The I-CeuI, PacI, and SwaI low-resolution map of P. stutzeri type strain CCUG 11256 shows the locations of 12 genes, including rrn operons and the origin of replication. I-CeuI digests of the 20 strains studied plus the positions of six genes allowed a comparison of the rrn backbone organization within genomovars; the four rrn operons seemed to be at similar locations with respect to the origin of replication, as did the rest of the genes. However, a comparison of I-CeuI cleavage maps of the genomovar reference strains revealed a diverse genome organization in the genomovars relative to rrn operons and gene locations. In most genomovars, rrn operons are not arranged around the origin of replication but are equally distributed on the chromosome. Strain JM300 does not belong to any described genomovar, as determined from the organization of its genome. Large chromosomal rearrangements seem to be responsible for the differences in superordinate genome structure and must have played an important role in P. stutzeri diversification and niche colonization. An ancestral chromosome is suggested, and some plausible pathways for the generation of the various genome structures are proposed.
为了确定斯氏假单胞菌内的基因组变异性，使用不同分辨率的稀有切割酶对代表七个已描述基因组群的20个菌株以及菌株JM300进行了分析。XbaI和SpeI指纹图谱显示出高度的限制性模式异质性，这与基因组群的划分不相关。然而，片段模式比较导致在基因组群内建立了几组克隆变体。一条大小在3.75至4.64 Mb之间的环状染色体构成了斯氏假单胞菌菌株的基因组。斯氏假单胞菌模式菌株CCUG 11256的I-CeuI、PacI和SwaI低分辨率图谱显示了12个基因的位置，包括rrn操纵子和复制起点。对所研究的20个菌株的I-CeuI消化产物以及六个基因的位置进行比较，可对基因组群内的rrn主干组织进行比较；四个rrn操纵子相对于复制起点似乎位于相似的位置，其他基因也是如此。然而，对基因组群参考菌株的I-CeuI切割图谱进行比较发现，相对于rrn操纵子和基因位置，基因组群中的基因组组织各不相同。在大多数基因组群中，rrn操纵子并非围绕复制起点排列，而是在染色体上均匀分布。从其基因组组织来看，菌株JM300不属于任何已描述的基因组群。大型染色体重排似乎是上级基因组结构差异的原因，并且一定在斯氏假单胞菌的多样化和生态位定殖中发挥了重要作用。本文提出了一个祖先染色体，并提出了一些产生各种基因组结构的合理途径。
