Miller W L, Pabbaraju K, Sanderson K E
Salmonella Genetic Stock Centre, Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada T2N 1N4.
J Bacteriol. 2000 Feb;182(4):1109-17. doi: 10.1128/JB.182.4.1109-1117.2000.
Intervening sequences (IVSs) were originally identified in the rrl genes for 23S rRNA (rrl genes, for large ribosomal subunit, part of rrn operon encoding rRNA) of Salmonella enterica serovars Typhimurium LT2 and Arizonae. These sequences are transcribed but later removed during RNase III processing of the rRNA, resulting in fragmentation of the 23S species; IVSs are uncommon, but have been reported in at least 10 bacterial genera. Through PCR amplification of IVS-containing regions of the rrl genes we showed that most Proteus and Providencia strains contain IVSs similar to those of serovar Typhimurium in distribution and location in rrl genes. By extraction and Northern blotting of rRNA, we also found that these IVSs result in rRNA fragmentation. We report the first finding of two very different sizes of IVS (113 bp and 183 to 187 bp) in different rrl genes in the same strain, in helix 25 of Proteus and Providencia spp.; IVSs from helix 45 are 113 to 123 bp in size. Analysis of IVS sequence and postulated secondary structure reveals striking similarities of Proteus and Providencia IVSs to those of serovar Typhimurium, with the stems of the smaller IVSs from helix 25 being similar to those of Salmonella helix 25 IVSs and with both the stem and the central loop domain of helix 45 IVSs being similar. Thus, IVSs of related sequences are widely distributed throughout the Enterobacteriaceae, in Salmonella, Yersinia, Proteus, and Providencia spp., but we did not find them in Escherichia coli, Citrobacter, Enterobacter, Klebsiella, or Morganella spp.; the sporadic distribution of IVSs of related sequence indicates that lateral genetic transfer has occurred.
间隔序列（IVSs）最初是在肠炎沙门氏菌鼠伤寒血清型LT2和亚利桑那血清型的23S rRNA的rrl基因（rrl基因，用于大核糖体亚基，是编码rRNA的rrn操纵子的一部分）中发现的。这些序列被转录，但随后在rRNA的RNase III加工过程中被去除，导致23S种类的片段化；IVSs并不常见，但已在至少10个细菌属中被报道。通过对rrl基因含IVS区域的PCR扩增，我们发现大多数变形杆菌和普罗威登斯菌菌株含有与鼠伤寒血清型在rrl基因中的分布和位置相似的IVSs。通过rRNA的提取和Northern印迹分析，我们还发现这些IVSs导致rRNA片段化。我们首次发现在同一菌株的不同rrl基因中存在两种大小差异很大的IVS（113 bp和183至187 bp），位于变形杆菌和普罗威登斯菌属的螺旋25中；来自螺旋45的IVSs大小为113至123 bp。对IVS序列和推测的二级结构的分析揭示了变形杆菌和普罗威登斯菌的IVSs与鼠伤寒血清型的IVSs有显著相似性，来自螺旋25的较小IVSs的茎与沙门氏菌螺旋25 IVSs的茎相似，螺旋45 IVSs的茎和中心环结构域都相似。因此，相关序列的IVSs广泛分布于整个肠杆菌科，包括沙门氏菌、耶尔森氏菌、变形杆菌和普罗威登斯菌属，但我们在大肠杆菌、柠檬酸杆菌、肠杆菌、克雷伯氏菌或摩根氏菌属中未发现它们；相关序列IVSs的零星分布表明发生了横向基因转移。
