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Mycobacterium avium subsp. paratuberculosis (Map) Fatty Acids Profile Is Strain-Dependent and Changes Upon Host
Marta Alonso-Hearn1, Naiara Abendaño1, Maria A Ruvira2
1Department of Animal Health, NEIKER-Basque Institute for Agricultural Research and Development, Technological Park of Bizkaia Derio, Spain.
Abstract:
Johne's disease is a chronic granulomatous enteritis of ruminants caused by the intracellular bacterium Mycobacterium avium subsp. paratuberculosis (Map). We previously demonstrated that Map isolates from sheep persisted within host macrophages in lower CFUs than cattle isolates after 7 days of infection. In the current study, we hypothesize that these phenotypic differences between Map isolates may be driven be the fatty acids (FAs) present on the phosphadidyl-1-myo-inositol mannosides of the Map cell wall that mediate recognition by the mannose receptors of host macrophages. FAs modifications may influence Map's envelope fluidity ultimately affecting pathogenicity. To test this hypothesis, we investigated the responses of two Map isolates from cattle (K10 isolate) and sheep (2349/06-1) to the bovine and ovine macrophage environment by measuring the FAs content of extracellular and intracellular bacteria. For this purpose, macrophages cell lines of bovine (BOMAC) and ovine (MOCL-4) origin were infected with the two isolates of Map for 4 days at 37°C. The relative FAs composition of the two isolates recovered from infected BOMAC and MOCL-4 cells was determined by gas chromatography and compared with that of extracellular bacteria and that of bacteria grown in Middlebrook 7H9 medium. Using this approach, we demonstrated that the FAs composition of extracellular and 7H9-grown bacteria was highly conserved within each Map isolate, and statistically different from that of intracellular bacteria. Analysis of FAs composition from extracellular bacteria enabled the distinction of the two Map strains based on the presence of the tuberculostearic acid (18:0 10Me) exclusively in the K10 strain of Map. In addition, significant differences in the content of Palmitic acid and cis-7 Palmitoleic acid between both isolates harvested from the extracellular environment were observed. Once the infection established itself in BOMAC and MOCL-4 cells, the FAs profiles of both Map isolates appeared conserved. Our results suggest that the FAs composition of Map might influence its recognition by macrophages and influence the survival of the bacillus within host macrophages.
Insights
Fatty acids on Mycobacterium avium subsp. paratuberculosis cell walls influence macrophage interaction. Differences in fatty acid profiles distinguish cattle and sheep isolates, impacting bacterial survival within host macrophages.
Area of Science:
- Microbiology
- Immunology
- Veterinary Science
Background:
- Johne's disease is a ruminant enteritis caused by Mycobacterium avium subsp. paratuberculosis (Map).
- Previous studies showed sheep Map isolates have lower persistence in macrophages than cattle isolates.
- Phenotypic differences may stem from fatty acids (FAs) on Map's cell wall, affecting macrophage recognition.
Purpose of the Study:
- To investigate how Map isolates from cattle and sheep respond to bovine and ovine macrophage environments.
- To determine if differences in cell wall fatty acid composition influence Map's interaction with host macrophages.
Main Methods:
- Bovine (BOMAC) and ovine (MOCL-4) macrophage cell lines were infected with Map isolates (cattle K10, sheep 2349/06-1).
- Fatty acid composition of intracellular and extracellular Map was analyzed using gas chromatography.
- Bacterial FAs were compared between isolates and growth conditions (in vitro vs. intracellular).
Main Results:
- Extracellular and in vitro grown Map FAs were conserved within isolates but differed from intracellular bacteria.
- Tuberculostearic acid (18:0 10Me) was exclusively found in the cattle K10 isolate.
- Significant differences in Palmitic acid and cis-7 Palmitoleic acid content were observed between isolates in the extracellular environment.
Conclusions:
- Map fatty acid composition differs between cattle and sheep isolates, particularly in the extracellular environment.
- Intracellular Map exhibits altered fatty acid profiles compared to extracellular bacteria.
- These findings suggest Map's fatty acid composition influences macrophage recognition and intracellular survival.