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Moraxella catarrhalis phase-variable loci show differences in expression during conditions relevant to disease
Aimee Tan1, Luke V Blakeway1, Taha1
1Institute for Glycomics, Griffith University, Gold Coast, Queensland, Australia.
Plos One
|June 20, 2020
Summary
Moraxella catarrhalis uses phase variation, switching gene expression via DNA repeats, to adapt to the human host. This study identifies new phase-variable genes, revealing how repeat length changes impact bacterial adaptation during infection.
Area of Science:
- Microbiology
- Bacterial Pathogenesis
- Genetics
Background:
- Moraxella catarrhalis is a key pathogen in respiratory infections like otitis media and COPD exacerbations.
- Phase variation, driven by DNA repeats, allows bacteria to adapt to host environments and evade immune responses.
Purpose of the Study:
- To identify and characterize phase-variable genes in Moraxella catarrhalis.
- To investigate how simple sequence repeat (SSR) variation influences gene expression during host-mimicking conditions.
Main Methods:
- Bioinformatic analysis of M. catarrhalis genomes to identify SSR tracts.
- Experimental assays to measure SSR variation and gene expression (mRNA levels) under simulated infection conditions (biofilm, human serum).
Main Results:
- Seventeen SSR tracts were identified as potentially mediating phase variation in M. catarrhalis.
- Phase variation of ubiquitous surface protein A1 (uspA1) and A2 (uspA2) was observed under specific host-mimicking conditions.
- Two novel phase-variable genes, encoding a DNA methyltransferase (modO) and a hypothetical permease, were identified and confirmed.
Conclusions:
- M. catarrhalis possesses a significant repertoire of phase-variable genes regulated by SSRs.
- Changes in SSR length are responsible for modulating gene expression in response to host-relevant stimuli.
- Understanding phase variation is crucial for developing strategies against M. catarrhalis infections.
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