Microbial diversity in Calamita ferromagnetic sand

Thermophilic waste air treatment of an airborne ethyl acetate/toluene mixture in a bubble column reactor: Stability towards temperature changes

Thermophilic waste air treatment in a lab-scale bubble column reactor (BCR) was used to remove an ethyl acetate/toluene mixture under both mesophilic and thermophilic conditions, at 30-50 °C. Additional tests, e.g., toluene mass transfer measurement and monitoring of microbial population development, explained the observed bioreactor response to the conducted loading tests and temperature changes. The maximum overall elimination capacity at thermophilic conditions (50 °C) was 136.9 g·m^-3 h^-1, however hysteresis in elimination capacity was observed in response to ascending/descending temperature and inlet concentration changes. Representatives of genera Cupriavidus, Variovorax and order Rhodospirillales were found to be predominant in the degrading microbial population, depending on the operating temperature. Thermobacillus and Blastocatella were abundant at high (50 °C) and low (30 °C) temperatures, respectively. The observed gradual shift in microbial population caused a small yet significant gradual change in developing a preference for toluene at the expense of ethyl acetate, which explains the observed hysteresis. Yet, the whole bioreactor removal efficiency remained similar at the same temperature, thus demonstrating the advantages of using thermophiles in bioreactors with temperature variation, such as robustness and flexibility.

Exploration of Deinococcus-Thermus molecular diversity by novel group-specific PCR primers

The deeply branching Deinococcus-Thermus lineage is recognized as one of the most extremophilic phylum of bacteria. In previous studies, the presence of Deinococcus-related bacteria in the hot arid Tunisian desert of Tataouine was demonstrated through combined molecular and culture-based approaches. Similarly, Thermus-related bacteria have been detected in Tunisian geothermal springs. The present work was conducted to explore the molecular diversity within the Deinococcus-Thermus phylum in these extreme environments. A set of specific primers was designed in silico on the basis of 16S rRNA gene sequences, validated for the specific detection of reference strains, and used for the polymerase chain reaction (PCR) amplification of metagenomic DNA retrieved from the Tataouine desert sand and Tunisian hot spring water samples. These analyses have revealed the presence of previously undescribed Deinococcus-Thermus bacterial sequences within these extreme environments. The primers designed in this study thus represent a powerful tool for the rapid detection of Deinococcus-Thermus in environmental samples and could also be applicable to clarify the biogeography of the Deinococcus-Thermus phylum.