Correct option is C
The correct answer is (c) because Mycobacterium tuberculosis (M. tuberculosis) has evolved a survival strategy that allows it to persist inside host macrophages. After being internalized via phagocytosis, M. tuberculosis resides in phagosomes, but unlike E. coli, it actively prevents the maturation of phagosomes into phagolysosomes. This evasion strategy is critical for its survival and replication within host cells.
M. tuberculosis interferes with the recruitment and function of proteins (like Rab7 and VPS33B) that are necessary for the fusion of phagosomes with lysosomes. As a result, the phagosomes remain in an immature state, lacking the acidic and hydrolytic environment required to kill the pathogen, enabling M. tuberculosis to avoid degradation.
Information Booster:
- M. tuberculosis is phagocytosed by macrophages but survives intracellularly.
- It blocks the transition of early phagosomes to mature phagolysosomes.
- This is achieved by inhibiting acidification and the recruitment of lysosomal fusion proteins.
- The bacteria manipulate host cell signaling pathways to avoid degradation.
- This mechanism is a hallmark of M. tuberculosis pathogenesis and persistence.
- Unlike E. coli, which is rapidly destroyed in phagolysosomes, M. tuberculosis creates a protective niche.
- Targeting phagosome maturation pathways is a potential strategy in tuberculosis therapy.
Additional Information:
- (a) Internalization by pinocytosis: Incorrect — Pinocytosis is nonspecific fluid-phase uptake, not the primary method of bacterial entry.
- (b) Internalization by autophagy: Incorrect — Autophagy is a degradation process for damaged organelles or proteins; although it may target some intracellular pathogens, it is not the main mechanism here.
- (d) Prevention of lysosome generation: Incorrect — Lysosomes are still generated in macrophages; M. tuberculosis only prevents fusion of lysosomes with phagosomes, not lysosome formation.
