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Updated: May 11, 2026
Using a Bacterial Pathogen to Probe for Cellular and Organismic-level Host Responses
Published on: February 22, 2019
MalF is essential for persistence of Mycoplasma gallisepticum in vivo
Chi-Wen Tseng1, Anna Kanci1, Christine Citti2,3
1Asia-Pacific Centre for Animal Health, Faculty of Veterinary Science, The University of Melbourne, Parkville, Victoria 3010, Australia.
Abstract:
There is limited understanding of the molecular basis of virulence in the important avian pathogen Mycoplasma gallisepticum. To define genes that may be involved in colonization of chickens, a collection of mutants of the virulent Ap3AS strain of M. gallisepticum were generated by signature-tagged transposon mutagenesis. The collection included mutants with single insertions in the genes encoding the adhesin GapA and the cytadherence-related protein CrmA, and Western blotting confirmed that these mutants did not express these proteins. In two separate in vivo screenings, two GapA-deficient mutants (ST mutants 02-1 and 06-1) were occasionally recovered from birds, suggesting that GapA expression may not always be essential for persistence of strain Ap3AS. CrmA-deficient ST mutant 33-1 colonized birds poorly and had reduced virulence, indicating that CrmA was a significant virulence factor, but was not absolutely essential for colonization. ST mutant 04-1 contained a single transposon insertion in malF, a predicted ABC sugar transport permease, and could not be reisolated even when inoculated by itself into a group of birds, suggesting that expression of MalF was essential for persistence of M. galliseptium strain Ap3AS in infected birds.
Insights
Mycoplasma gallisepticum virulence factors were investigated using transposon mutagenesis. MalF, an ABC sugar permease, proved essential for M. gallisepticum persistence in chickens, while GapA and CrmA were less critical.
Area of Science:
- Avian Pathogen Research
- Bacterial Virulence Mechanisms
- Molecular Microbiology
Background:
- Mycoplasma gallisepticum is a significant avian pathogen with poorly understood virulence factors.
- Identifying genes involved in M. gallisepticum colonization is crucial for controlling avian respiratory diseases.
Purpose of the Study:
- To identify genes essential for the colonization and persistence of Mycoplasma gallisepticum strain Ap3AS in chickens.
- To elucidate the roles of specific adhesins and transport proteins in M. gallisepticum pathogenesis.
Main Methods:
- Signature-tagged transposon mutagenesis was employed to generate a library of M. gallisepticum mutants.
- Mutants deficient in adhesin GapA and cytadherence protein CrmA were characterized.
- In vivo competition assays and single-inoculum screenings were performed in chickens to assess mutant recovery and virulence.
Main Results:
- GapA-deficient mutants were occasionally recovered, suggesting GapA is not always essential for persistence.
- CrmA-deficient mutants exhibited reduced colonization and virulence, indicating CrmA is a significant but not essential virulence factor.
- A mutant with a transposon insertion in malF (ABC sugar transport permease) was unable to persist in chickens, highlighting MalF's essential role.
Conclusions:
- The MalF permease is critical for the persistence of Mycoplasma gallisepticum strain Ap3AS in avian hosts.
- While GapA and CrmA contribute to virulence, their absence does not completely abolish colonization, unlike MalF.
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