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Identification of a possible cytadherence regulatory locus in Mycoplasma pneumoniae
1Department of Microbiology, University of Georgia, Athens 30602, USA.
Abstract:
Transposon mutagenesis was used to analyze Mycoplasma pneumoniae cytadherence. Mycoplasmas were electroporated with Tn4001, and transformants were identified by antibiotic selection using gentamicin. The resulting colonies were screened for hemadsorption (HA) as an indicator for cytadherence. Six HA- colonies from independent transformations were isolated, filter cloned, and characterized in more detail. Southern hybridization analysis revealed that all six transposon insertions mapped to the same 252-kbp ApaI fragment and 19.5-kbp XhoI fragment. More detailed analysis localized the insertion to two adjacent EcoRI fragments. This site is distinct from the locus containing the genes for the high-molecular weight cytadherence-accessory proteins HMW1 and HMW3, and yet these proteins were absent from the protein profiles of all six transformants. To determine if transposon insertion was responsible for the HA- phenotype, reversion frequencies of the transformants were assessed after passage in the presence of antibiotic selection. In contrast to a spontaneously arising HMW-deficient variant, which reverted to an HA+ phenotype readily, no HA+ revertants were identified for any of the six transformants. These observations suggest that a potential regulatory locus that may be important in the expression of the HMW cytadherence-accessory proteins has been identified.
Insights
Transposon mutagenesis identified a new regulatory locus in Mycoplasma pneumoniae essential for cytadherence. This locus controls the expression of high-molecular-weight proteins crucial for bacterial attachment.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- Mycoplasma pneumoniae causes respiratory infections.
- Cytadherence is crucial for M. pneumoniae pathogenesis.
- High-molecular-weight (HMW) proteins are key adhesins.
Purpose of the Study:
- To identify genetic factors regulating M. pneumoniae cytadherence.
- To investigate the role of a novel locus in HMW protein expression.
Main Methods:
- Transposon mutagenesis using Tn4001.
- Antibiotic selection and hemadsorption screening for cytadherence.
- Southern hybridization for mapping transposon insertions.
- Protein profile analysis and reversion frequency assessment.
Main Results:
- Six independent transposon insertions mapped to a specific DNA region.
- This locus is distinct from known HMW protein genes.
- Transposon mutants showed a complete absence of HMW1 and HMW3 proteins.
- Mutants failed to revert to a cytadherent phenotype, indicating stable disruption.
Conclusions:
- A novel regulatory locus controlling HMW protein expression in M. pneumoniae was identified.
- This locus is critical for M. pneumoniae cytadherence.
- Further research into this regulatory locus could reveal new therapeutic targets.