Comín Jessica, Otal Isabel, Samper Sofía
Unidad de Investigación Traslacional, Hospital Universitario Miguel Servet, Instituto Aragonés de Ciencias de la Salud, Zaragoza, Spain.
Fundación IIS Aragón, Zaragoza, Spain.
Front Microbiol. 2022 Feb 24;13:767912. doi: 10.3389/fmicb.2022.767912. eCollection 2022.
The insertion sequence (IS) is a repetitive mobile element specific for the complex (MTBC) used for years to diagnose and genotype this pathogen. It contains the overlapping reading frames and that encode a transposase. Its genetic variability is difficult to study because multiple copies are present in the genome. IS is randomly located, nevertheless some preferential locations have been reported, which could be related to the behaviour of the strains. The aim of this work was to determine the intra- and inter-strain genetic conservation of this element in the MTBC. For this purpose, we analysed 158 sequences of IS copies from 55 strains. Eighty-four copies were from 17 strains for which we knew all the locations in their genome. In addition, we studied 74 IS copies in 38 different MTBC strains in which the location was characteristic of different families including Haarlem, LAM, S, and L6 strains. We observed mutation in 13.3% of the copies studied and we found 10 IS variants in 21 copies belonging to 16 strains. The high copy number strains showed 6.2% of their IS copies mutated, in contrast with the 31.1% in the low-copy-number strains. The apparently more ancient copy localised in the DR region was that with more variant copies, probably because this was the most studied location. Notably, all Haarlem and X family strains studied have an IS in , suggesting a common origin for both families. Nevertheless, we detected a variant specific for the X family that would have occurred in this location after the phylogenetic separation. This variant does not prevent transposition although it may occur at a lower frequency, as X strains remain with low copy number (LCN) of IS.
插入序列（IS）是结核分枝杆菌复合群（MTBC）特有的一种重复移动元件，多年来一直用于该病原体的诊断和基因分型。它包含重叠的读框 和 ，编码一种转座酶。由于基因组中存在多个拷贝，其遗传变异性难以研究。IS是随机定位的，不过已有报道称存在一些优先定位，这可能与菌株的行为有关。这项工作的目的是确定MTBC中该元件的菌株内和菌株间遗传保守性。为此，我们分析了来自55个菌株的158个IS拷贝序列。84个拷贝来自17个菌株，我们知道它们在基因组中的所有位置。此外，我们研究了38个不同MTBC菌株中的74个IS拷贝，这些菌株的定位具有不同家族的特征，包括哈勒姆家族、LAM家族、S家族和L6家族。我们在所研究的拷贝中有13.3%观察到突变，并且在属于16个菌株的21个拷贝中发现了10种IS变体。高拷贝数菌株的IS拷贝有6.2%发生突变，相比之下，低拷贝数菌株为31.1%。定位在DR区域的明显更古老的拷贝具有更多的变体拷贝，可能是因为这是研究最多的位置。值得注意的是，所有研究的哈勒姆家族和X家族菌株在 中都有一个IS，这表明这两个家族有共同的起源。然而，我们检测到一个X家族特有的变体，它可能在系统发育分离后出现在这个位置。尽管它可能以较低的频率发生，但这个变体并不妨碍转座，因为X菌株的IS拷贝数仍然较低（LCN）。
