MICROBIOLOGY: Getting Enough Air to Survive

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Science  17 May 2002:
Vol. 296, Issue 5571, pp. 1203d
DOI: 10.1126/science.296.5571.1203d

After infection by tubercle bacteria, the host battles the invader to a standoff, at least as long as the immune system functions effectively. Upon entry, the pathogen subversively invades the immune system through inactivated macrophages; the distressed and infected host cells then emit signals that recruit activated macrophages to encapsulate the site of infection in a characteristic granuloma, or tubercle. Nitric oxide (NO) produced by these macrophages controls pathogen growth by inhibiting aerobic respiration in the bacteria and contributing to the formation of toxic peroxynitrite. Tubercle bacteria do not have flavohemoglobins (which other pathogens use to detoxify NO) but instead have three types of distinctive truncated hemoglobins (trHbs). Ouellet et al. have found that the trHbs act in concert in mycobacteria to acquire enough oxygen to support the conversion of NO into innocuous nitrate.—CA

Proc. Natl. Acad. Sci. U.S.A. 99, 5902 (2002).

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