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Open Access Research article

Acidochromogenicity is a common characteristic in nontuberculous mycobacteria

Beatrice Saviola* and Jeffrey Felton

Author Affiliations

Basic Medical Sciences, College of Osteopathic Medicine, Western University of Health Sciences, 309 E. Second St., Pomona, CA 91766, USA

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BMC Research Notes 2011, 4:466  doi:10.1186/1756-0500-4-466

Published: 29 October 2011



An acidic environment is something likely encountered by mycobacteria in the environment or in a human host. Previously mycobacterial species had been known to produce carotenoid pigments in response to light or constitutively.


We have tested the ability of various mycobacteria to grow on solid agar plates of differing acidity, and have shown that many species of mycobacteria previously thought to not produce pigment are pigmented when exposed to acidic stress. The Mycobacterium smegmatis promoter region upstream of the genes homologous to those of other mycobacterial species known to code for proteins involved in carotenoid biosynthesis was found to be upregulated under acidic stress.


Mycobacterial species can produce pigment in response to conditions not previously known to induce chromogenicity in mycobacteria. In addition many mycobacterial species previously thought to not produce pigment are actually chromogenic under acidic conditions.