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Published on: May 4, 2018
Reconstitution of an active arginine deiminase pathway in Mycoplasma pneumoniae M129
Hagai Rechnitzer1, Shlomo Rottem, Richard Herrmann
1Department of Microbiology and Molecular Genetics, The Hebrew University-Hadassah Medical School, Jerusalem, Israel.
Abstract:
Some species of the genus Mycoplasma code for the arginine deiminase pathway (ADI), which enables these bacteria to produce ATP from arginine by the successive reaction of three enzymes: arginine deiminase (ArcA), ornithine carbamoyltransferase (ArcB), and carbamate kinase (ArcC). It so far appears that independently isolated strains of Mycoplasma pneumoniae encode an almost identical truncated version of the ADI pathway in which the proteins ArcA and ArcB have lost their original enzymatic activities due to the deletion of significant regions of these proteins. To study the consequences of a functional ADI pathway, M. pneumoniae M129 was successfully transformed with the cloned functional arcA, arcB, and arcC genes from Mycoplasma fermentans. Enzymatic tests showed that while the M. pneumoniae ArcAB and ArcABC transformants possess functional arginine deiminase, ornithine carbamoyltransferase, and carbamate kinase, they were unable to grow on arginine as the sole energy source. Nevertheless, infection of a lung epithelial cell line, A549, with the M. pneumoniae transformants showed that almost 100% of the infected host cells were nonviable, while most of the lung cells infected with nontransformed M. pneumoniae were viable under the same experimental conditions.
Insights
Mycoplasma pneumoniae transformants gained a functional arginine deiminase pathway (ADI). Despite this, they couldn't metabolize arginine but significantly increased lung cell death, indicating a novel virulence mechanism.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Pathogenesis
Background:
- The arginine deiminase pathway (ADI) enables ATP production from arginine in some Mycoplasma species.
- Mycoplasma pneumoniae typically possesses a truncated, non-functional ADI pathway.
- Restoring ADI function in M. pneumoniae is crucial for understanding its role in virulence.
Purpose of the Study:
- To investigate the consequences of a functional ADI pathway in Mycoplasma pneumoniae.
- To determine if restoring ADI function impacts M. pneumoniae's growth or pathogenicity.
Main Methods:
- Cloning and transformation of functional arginine deiminase (ArcA), ornithine carbamoyltransferase (ArcB), and carbamate kinase (ArcC) genes from Mycoplasma fermentans into M. pneumoniae M129.
- Enzymatic assays to confirm the activity of the restored ADI pathway enzymes.
- Infection assays using the A549 lung epithelial cell line to assess host cell viability.
Main Results:
- Transformed M. pneumoniae strains (ArcAB and ArcABC) exhibited functional ArcA, ArcB, and ArcC enzymatic activities.
- Despite functional ADI enzymes, M. pneumoniae transformants could not utilize arginine as a sole energy source for growth.
- Infection with M. pneumoniae transformants resulted in nearly 100% nonviability of A549 lung cells, contrasting with the viability of cells infected by the wild-type strain.
Conclusions:
- Restoring the arginine deiminase pathway in M. pneumoniae does not enable arginine utilization for growth.
- The functional ADI pathway significantly enhances the virulence of M. pneumoniae, leading to increased host cell death.
- This study reveals a novel virulence mechanism for M. pneumoniae linked to the ADI pathway.
