The Intergovernmental Panel on Climate Change recommends keeping the increase in temperature to less than a two-degree increase by the end of the century, but the direct impact of global warming on ecosystems including microbes has not been investigated. Here we performed thermal adaptation of two species and three strains of mesophilic microbes for improvement of the survival upper limit of temperature, and the improvement was evaluated by a newly developed method. To understand the limitation and variation of thermal adaptation, experiments with mutators and by multiple cultures were performed. The results of experiments including genome sequencing and analysis of the characteristics of mutants suggest that these microbes bear a genomic potential to endure a 2–3°C rise in temperature but possess a limited variation of strategies for thermal adaptation.
A quartz crystal microbalance (QCM) was used to study the removal of stearic acid from poly(ethylene terephthalate) (PET) substrate in aqueous alkali and surfactant solutions. The PET substrate was prepared on a QCM gold electrode by spin-coating; its properties were examined by scanning electron microscopy, X-ray photoelectron spectroscopy, and water contact angle measurements. As a result, the QCM electrode was found to be completely covered with a smooth PET film. To investigate the effect of soil deposition state on its removal, stearic acid (an oily soil model) was deposited onto the PET substrate with the Langmuir-Blodgett (LB) technique or by spraying. The QCM frequency was recorded during the removal of stearic acid from the PET substrate in aqueous solutions. In NaOH solution, stearic acid deposited by the LB method was more rapidly removed than when deposited by the spraying method. However, the LB films of stearic acid were difficult to be removed in surfactant solutions. With respect to removal behavior of spray-deposited stearic acid in surfactant solutions, the results determined by the QCM method were compared with those from microscopic image analysis. The removal efficiencies in the sodium dodecyl sulfate solution were in good agreement between the two methods. However, in the alkyl ethoxylate solution, the removal efficiencies obtained by the QCM method were larger than those from microscopic image analysis. These experimental results were explained by the removal mechanism of stearic acid by the alkali and surfactant solutions.
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