Integrons found in different locations have identical 5' ends but variable 3' ends

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Integrons are genetic elements that play a crucial role in the dissemination of antibiotic resistance genes.
• Understanding the structural diversity and boundaries of integrons is essential for comprehending their evolution and mobility.

Purpose of the Study:

• To determine the precise locations of the outer boundaries of the 5'- and 3'-conserved segments in various integrons.
• To compare the structural organization of different integron families and identify conserved and variable regions.

Main Methods:

• Sequence analysis of six independently located integrons: In1 (R46), In2 (Tn21), In3 (R388), In4 (Tn1696), In5 (pSCH884), and In0 (pVS1).
• Comparative analysis of conserved and divergent sequences within the integrons.
• Identification of insertion sequences (IS6100) and inverted repeats flanking integron structures.

Main Results:

• The 5'-conserved segment's 5' end is conserved across all six studied integrons.
• Significant variation exists in the extent and sequence identity of the 3'-conserved segment among these integrons.
• Specific divergence points and deletions were identified in the 3'-conserved segments of In0 and In2.
• IS6100 insertions and inverted repeats were found associated with the conserved regions of certain integrons, suggesting potential mobility.

Conclusions:

• Integron structures exhibit a conserved 5' end but variable 3' ends, reflecting evolutionary divergence.
• While some integrons share features with transposable elements, definitive identification of all sequences associated with a functional transposon requires further investigation.
• The findings provide insights into integron structure, evolution, and potential mechanisms of gene acquisition and dissemination.