Exobiology and Evolutionary Biology

Protocells and the Emergence of Cellular Life

PI: Jack Szostak

The goal of the proposed research is to improve our understanding of the origin of cellular life on earth, and of the potential for life to arise on other planets. This proposal is focused on the laboratory synthesis of simple protocells that are able to reproduce and adapt through evolution. It is a continuation of work currently funded by the NASA Exobiology Program.

Our specific goals are:
1) to develop a complete model protocell in which both the nucleic acid genome and the cell membrane are capable of indefinite cycles of replication, and
2) to study potential pathways for the transition from primitive to modern cell membranes.
We will approach these goals using a wide range of physical and chemical methods. We use synthetic organic chemistry to make new lipids and nucleotides, and we use simple physical methods to make and purify vesicles that contain encapsulated genetic templates. We characterize these model protocells by a variety of biophysical techniques, including fluorescence methods and microscopy. Permeability studies will make use of methods based on NMR spectroscopy or fluorescence measurements. Studies of nucleic acid synthesis use standard molecular biology methods such as gel electrophoresis to follow the course of the reactions, complemented by mass spectrometry (MALDI-TOF) for product characterization.
The greatest significance of the proposed work lies in its potential for the discovery of new and surprising phenomena related to the origin of life. Our currently funded work led to the discovery of several very simple but completely unanticipated physical processes that simplify our thinking about the origin and reproduction of the first cells. Continuing efforts to synthesize model protocells are quite likely to lead to the discovery of additional unsuspected processes that may have played a role in the emergence of cellular life. A better understanding of the origin of life is central to the stated goals of the Astrobiology and Exobiology Programs of NASA. Moreover, an improved understanding of the conditions under which life could emerge, and of the possible nature of early living systems, will facilitate the search for life (or signs of extinct life) in other solar system environments such as Mars and Europa, as well as on exoplanets.