The IS6 family, a clinically important group of insertion sequences including IS26

Patricia Siguier,Michael Chandler,Susu He,Alessandro Varani,Karen Ross

doi:10.1186/s13100-021-00239-x

Abstract

The IS6 family of bacterial and archaeal insertion sequences, first identified in the early 1980s, has proved to be instrumental in the rearrangement and spread of multiple antibiotic resistance. Two IS, IS26 (found in many enterobacterial clinical isolates as components of both chromosome and plasmids) and IS257 (identified in the plasmids and chromosomes of gram-positive bacteria), have received particular attention for their clinical impact. Although few biochemical data are available concerning the transposition mechanism of these elements, genetic studies have provided some interesting observations suggesting that members of the family might transpose using an unexpected mechanism. In this review, we present an overview of the family, the distribution and phylogenetic relationships of its members, their impact on their host genomes and analyse available data concerning the particular transposition pathways they may use. We also provide a mechanistic model that explains the recent observations on one of the IS6 family transposition pathways: targeted cointegrate formation between replicons.

Highlights

The importance of insertion sequences (IS) in shaping prokaryotic genomes and in directing gene sequestration as a prologue to horizontal transfer in bacterial populations has been well documented
There are at least 27 IS families [3, 4] defined by the chemistry used by their Tnp, the sequence relatedness of the Tnp as defined [5] by TRIBE-MCL which relies on the Markov cluster (MCL) algorithm [6] and the sequence of their ends
Genomic impact and clinical importance Activity resulting in horizontal dissemination is suggested, for example, by the observation that copies identical to IS6100 originally identified in Mycobacterium fortuitum [47](Fig. 3, clade b) occur in other bacteria: as part of a plasmid-associated catabolic transposon carrying genes for nylon degradation in Arthrobacter sp. [48]; in the Pseudomonas aeruginosa plasmid R1003 [49]; and in integrons of the In4-type from transposons such as Tn1696 [50, 51] and Xanthomonas campestris transposon Tn5393b [52]

Summary

Introduction

The importance of insertion sequences (IS) in shaping prokaryotic genomes and in directing gene sequestration as a prologue to horizontal transfer in bacterial populations has been well documented (see [1, 2] and references therein for a detailed discussion). Genomic impact and clinical importance Activity resulting in horizontal dissemination is suggested, for example, by the observation that copies identical to IS6100 originally identified in Mycobacterium fortuitum [47](Fig. 3, clade b) occur in other bacteria: as part of a plasmid-associated catabolic transposon carrying genes for nylon degradation in Arthrobacter sp.

Results

Conclusion