Sequential adaptation in latent tuberculosis bacilli: observation by atomic force microscopy (AFM)

Area of Science:

• Microbiology
• Cell Biology
• Tuberculosis Research

Background:

• Mycobacterium tuberculosis (MTB) establishes latent infections in humans for years.
• The mechanisms of MTB latency, potentially triggered by low oxygen, are not fully understood.
• Studying anaerobic MTB cultures provides a model for latent tuberculosis.

Purpose of the Study:

• To investigate the sequential adaptation of Mycobacterium tuberculosis under anaerobic conditions over 48 months.
• To observe morphological and cellular changes associated with MTB latency using Atomic Force Microscopy (AFM).

Main Methods:

• Anaerobic culture of Mycobacterium tuberculosis (H37RV strain).
• Sequential sampling every 90 days for 48 months.
• Atomic Force Microscopy (AFM) for high-resolution imaging of bacterial morphology.

Main Results:

• Observed temporary adaptations (1-18 months): thickened cell walls, ovoid cell formation, size reduction, and budding division.
• Identified specialized cell development: spore-like cells and filterable, non-acid-fast forms.
• Non-acid-fast forms exhibited metabolic activity and symmetrical cell division, though not true spores.

Conclusions:

• MTB employs distinct adaptation strategies under oxygen-limited conditions.
• Changes in cell shape, size, and loss of acid-fastness are key survival mechanisms.
• Further research into these adaptations could inform tuberculosis treatment strategies.