1Surprisingly, highly contaminated environments, notably with heavy metals, organochlorines or hydrocarbons, can host very specific bacteria, Mesotoga. In the early 2000s, the presence of these bacteria in the environment was only known indirectly, through the use of molecular markers. As a result of studies conducted in 2011 on a Tunisian reactor treating industrial wastewater with high concentrations of heavy metals, a team of microbiologists finally managed to grow these bacteria (Mesotoga strain PhosAc3).

Stream contaminated with lead and tin, Bolivia.

2Two species belonging to this bacterial genus have been described to date, Mesotoga prima and M. infera. They belong to the order Thermotogales, anaerobic bacteria which had only been found in warm ecosystems such as hydrothermal springs or oil field water. Their presence in lower-temperature environments (30-45°C) therefore constitutes a puzzle in bacterial evolution that researchers are trying to solve.  To enhance the growth of Mesotoga, researchers had the idea of cultivating Mesotoga with another bacterium capable of producing sulphides from sulfate. This operation was a success and enhanced the researchers’ understanding of the metabolism of Mesotoga.

Mesotoga, optical microscopy.

3This bacterial combination, protected by two patents, could therefore be used to “bioremedy” environments contaminated with hydrocarbons, BTEX (benzene, toluene, ethylbenzene, xylene), organochlorines or heavy metals as a result of anthropogenic activities. From a more fundamental point of view, studying the genome of Mesotoga will shed light on the evolutionary transition which allowed microorganisms to switch from life at a low temperature to life at a high temperature or vice versa.