Extraordinary solute-stress tolerance contributes to the environmental tenacity of mycobacteria

Ricardo Santos, Carla C. C. R. de Carvalho, Andrew Stevenson, Irene R. Grant, John E. Hallsworth

Research output: Contribution to journalArticlepeer-review

22 Citations (Scopus)


Mycobacteria are associated with a number of well-characterized diseases, yet we know little about their stress-biology in natural ecosystems. This study focuses on the isolation and characterization of strains from Yellowstone-(YNP) and Glacier-National-Parks (GNP; USA), the majority of those identified were Mycobacterium parascrofulaceum, Mycobacterium avium (YNP) or Mycobacterium gordonae (GNP). Generally, their temperature windows for growth were >60°C; selected isolates grew at super-saturated concentrations of hydrophobic stressors and at levels of osmotic stress and chaotropic activity (up to 13.4 kJkg-1) similar to, or exceeding, those for the xerophilic fungus Aspergillus wentii and solvent-tolerant bacterium Pseudomonas putida. For example, mycobacteria grew down to 0.800 water-activity indicating that they are, with the sole exception of halophiles, more xerotolerant than other bacteria (or any Archaea). Furthermore, the fatty-acid composition of Mycobacterium cells grown over a range of salt concentrations changed less than that of other bacteria, indicating a high level of resilience, regardless of the stress load. Cells of M. parascrofulaceum, M. smegmatis and M. avium resisted the acute, potentially lethal challenges from extremes of pH (<1; >13), and saturated MgCl2-solutions (5 M; 212 kJ kg-1 chaotropicity). Collectively, these findings challenge the paradigm that bacteria have solute tolerances inferior to those of eukaryotes.
Original languageEnglish
Pages (from-to)746-764
Number of pages19
Issue number5
Early online date29 Jul 2015
Publication statusPublished - 20 Oct 2015


  • Environmental Microbiology
  • Hydrogen-Ion Concentration
  • Hydrophobic and Hydrophilic Interactions
  • Microbial Viability
  • Mycobacterium
  • Osmotic Pressure
  • Parks, Recreational
  • Salts
  • Stress, Physiological
  • Temperature
  • United States
  • Journal Article
  • Research Support, Non-U.S. Gov't

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