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Ultrastructural study of mycobacteria in experimentally produced lung lesions of mice
Abstract:
Mice were infected by iv injection with a virulent strain of Mycobacterium bovis, Ravenel strain, to prepare specimens for electron microscopical observation of their intracellular morphology. Observation was made with ultra-thin sections of the granulomatous lungs at an advanced stage of infection. Many apparently intact bacterial cells were found intracellulary, and the majority of them had lipoidal inclusions enclosed by a membranous structure. Several layers of mycobacterial cell wall were discernible, including a fairly wide space of the electron-transparent zone just beneath the electrondense outmost layer. Mesosomes, nuclear material, small dense granules and cross wall were found in almost the same appearance as those reported of mycobacteria grown in vitro. The bacilli were located mainly within intact or damaged phagosomes which were often filled with amorphous material of various electron densities.
Insights
Electron microscopy revealed Mycobacterium bovis intracellular morphology in mouse lungs. Intact bacilli with lipoidal inclusions were observed within phagosomes, showing typical cell wall structures.
Area of Science:
- Microbiology
- Immunology
- Cell Biology
Background:
- Mycobacterium bovis infection causes granulomatous lung disease.
- Understanding intracellular bacterial morphology is crucial for host-pathogen interaction studies.
Purpose of the Study:
- To investigate the intracellular morphology of Mycobacterium bovis (Ravenel strain) in infected mouse lungs using electron microscopy.
- To characterize the ultrastructural features of M. bovis within host cells during advanced infection.
Main Methods:
- Infection of mice with Mycobacterium bovis (Ravenel strain) via intravenous injection.
- Preparation of granulomatous lung tissues from infected mice.
- Ultra-thin sectioning and electron microscopical observation of intracellular bacterial morphology.
Main Results:
- Intact Mycobacterium bovis bacilli were observed intracellularly within phagosomes.
- The majority of intracellular bacilli contained lipoidal inclusions enclosed by a membrane.
- Distinct layers of the mycobacterial cell wall, including an electron-transparent zone, were visible.
- Intracellular structures like mesosomes, nuclear material, and granules resembled those of in vitro grown mycobacteria.
- Bacilli were found in both intact and damaged phagosomes, often containing amorphous material.
Conclusions:
- Mycobacterium bovis maintains its structural integrity within host phagosomes during advanced lung infection.
- The presence of lipoidal inclusions suggests intracellular lipid metabolism or storage by M. bovis.
- Electron microscopy provides detailed insights into the ultrastructural adaptations of M. bovis within the host environment.