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Identification of an insertion-sequence-like genetic element in the newly recognized human pathogen Mycoplasma
1Department of Infectious and Parasitic Diseases Pathology, Armed Forces Institute of Pathology, Washington, DC 20306.
Abstract:
Cloned 2.2-kb DNA (plasmid psb-2.2) of Mycoplasma incognitus, a pathogen in AIDS and non-AIDS patients [Lo et al., Am. J. Trop. Med. Hyg. 41 (1989) 364-376; 601-616], contains a 1405-bp genetic element closely resembling bacterial insertion sequence (IS) elements. This IS-like element has 29-bp terminal inverted repeats with seven mismatches, is immediately flanked by 3-bp direct repeats, and has typical stem-and-loop structures at or near both the termini. Two potential open reading frames (ORF-1 and ORF-2) encode 143 amino acids (aa) and 103 aa, respectively, in this IS-like element. Part (57 aa) of the deduced aa sequence of ORF-2 has a significant homology (43%) with the putative transposase of Escherichia coli IS3. In this study, a series of synthetic oligodeoxyribonucleotides each containing a specific sequence of a selected segment in psb-2.2, have been used as probes which reveal that the IS-like element occurs more than ten times in the genome of M. incognitus. This potentially transposable element has many characteristic features in common with bacterial IS elements.
Insights
A novel insertion sequence-like element was identified in Mycoplasma incognitus, a pathogen linked to AIDS. This element, found multiple times in the genome, shares characteristics with bacterial insertion sequences.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Mycoplasma incognitus is a pathogen implicated in AIDS and non-AIDS related illnesses.
- Understanding the genetic makeup of M. incognitus is crucial for pathogen research.
Purpose of the Study:
- To characterize a novel genetic element found in the plasmid psb-2.2 of Mycoplasma incognitus.
- To investigate the potential transposable nature and genomic distribution of this element.
Main Methods:
- Cloning and sequencing of the 2.2-kb DNA fragment (plasmid psb-2.2).
- Bioinformatic analysis to identify genetic elements and predict protein sequences.
- Use of synthetic oligodeoxyribonucleotides as probes for genomic analysis.
Main Results:
- A 1405-bp insertion sequence (IS)-like element was identified within psb-2.2.
- The element exhibits terminal inverted repeats, flanking direct repeats, and stem-and-loop structures.
- Two open reading frames (ORFs) were identified, with ORF-2 showing homology to the transposase of E. coli IS3.
- The IS-like element was found to occur more than ten times in the M. incognitus genome.
Conclusions:
- The identified element in M. incognitus possesses key features characteristic of bacterial IS elements.
- This potentially transposable element may play a role in the genome plasticity of M. incognitus.