PhD thesis

Spectroscopic and calorimetric investigation of the physical basis of anhydrobiosis in Caenorhabditis elegans

PhD student:
Sawsan E. Abu Sharkh
Dr. Karim Fahmy (HZDR), Prof. Teymuras Kurzchalia and Prof. Stefan Diez (MPI-CBG)


The nematode Caenorhabditis elegans is a model organism for the study of development, aging and cell biology. It exhibits a variety of adaptations and undergoes temporary quiescence in response to environmental stress. Particularly, the organism can survive harsh conditions such as over crowding or starvation by forming a specific state, i.e. the so called dauer (enduring) larva. Dauer larva show a very distinct metabolism, morphology and enhanced stress resistance. In the dauer state, the life cycle can be interrupted in response to desiccation after a preconditioning phase rendering this nematode a well suited system to study the physical requirements of anhydrobiosis in an organism whose genome is fully known. It has been shown recently, that trehalose is essential in conferring desiccation tolerance and preliminary experiments from our lab indicate that it helps preserving lipid packing and probably the dispersion of fat droplets.

Aims of the study

This study aims to determine the hydration sensitive phase transitions of C.elegans-specific phospholipids and triglycerides in complex with the interaction of lanthanides and actinides with lipids and trehalose in vitro using FTIR spectroscopy, Langmuir-Blodget films and differential scanning calorimetry to reveal the structural and the energetic aspects.

The effect of trehalose on purified lipidic components will be studied. In addition to the in vitro physio-chemical experiments, a system biology approach will be used to monitor the onset of metabolic activity by microcalorimetry upon exiting anhydrobiosis.

In both approaches, the specific role of trehalose and effects of radionuclides in the physiology and ecology of C.elegans will be addressed by using established strains of C.elegans that differ in their ability to synthesize trehalose, exhibit physiological as well as morphological manifestations of the different degrees of desiccation tolerance and may provide systems that can be adjusted to the degree of toxicity of different contaminants for (radio) ecological studies.

In vivo studies will address the metal-dependent exit from Dauer stage using microcalorimetry. In vitro studies will monitor the influence of metals on trehalose-lipid interactions as a potential molecular mechanism in both desiccation tolerance of the anhydrobiotic Dauer state and in metal toxicity.