Alkaliphilic Life
Adaptation strategies by Caldalkalibacillus thermarum
S.I. de Jong (TU Delft - BT/Environmental Biotechnology)
Mark C.M. van Loosdrecht – Promotor (TU Delft - BT/Environmental Biotechnology)
D.G.G. McMillan – Copromotor (TU Delft - BT/Biocatalysis)
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Abstract
Alkaliphiles thrive in environments with a pH of 8.5 or above, while maintaining an internal pH closer to neutral. Thus, alkaliphilic microorganisms have a proton gradient inverted with respect to the normal orientation. Intuitively, this would nullify the potential to generate energy via respiration with regularly oriented respiratory chains that rely on proton-coupled ATP synthases. Yet, alkaliphilic respiratory chains are oriented traditionally and are actively used. The question therefore is how they are able to create conditions conducive to such behaviour. In addition, attempts to answer that question will hopefully also clarify how alkaliphiles acidify their cytoplasm with respect to the exterior milieu in the first place. This thesis details methods required to study these questions and provides some answers regarding alkaliphilic life. This thesis focuses on a single category of alkaliphiles: the low-salt gram positive alkaliphiles. These microbes have just a single membrane, the proteins therein, and a cell wall to generate conditions suitable for energy generation and other transport mechanisms. In short, it can be regarded as the most basic system to study an alkaline, or basic, problem....