Iron, Tuberculosis, and Particle-Related Exposures Including Smoking.

The availability of iron controls the abundance and diversity of life. Microbial pathways for iron acquisition account for their replication and virulence. The balance of interactions defining a microbial community can be altered by environmental stress. Decreased iron availability applies a selective pressure that results in increased competition for the metal. The complexation of the host metal by cigarette smoke and other particles induces a functional iron deficiency in the respiratory tract of the exposed individual. M. tuberculosis is at an advantage in environments of decreased iron availability after cigarette smoking and other particle exposures as it possesses numerous pathways for metal acquisition. Accordingly, smoking and other particle exposures (e.g., air pollution, burning of biomass, and silica) are associated with increased tuberculosis infections.