Read below to explore a summary of the full “Alternative Chemistries of Life” report.
Genesis of the Workshop and Report
In April of 2012, researchers from Emory University, Arizona State University, the University of Utah, and the University of Washington jointly hosted a workshop, sponsored by the National Science Foundation (NSF) and the National Aeronautics and Space Administration (NASA), focused on research into alternatives chemistries of life. Such research opportunities are driven by the emergence of numerous technologies, including metagenomic analyses and meta-data processing, as well as rapidly accelerating discoveries of exoplanets beyond our solar system. The purpose of the workshop was to bring together diverse scientific communities that have not historically collaborated but could directly guide these opportunities and engage in them. Chemists, physicists, microbiologists, and virologists among many diverse researchers came together in this workshop to discuss alternative chemistries research from their distinct perspectives. Many fundamental topics were addressed, including alterative biopolymer backbones, novel chemical reactivity within dynamic networks, and the emergent properties of macromolecular assemblies and complex systems that constitute living matter.
We have done our very best to capture the richness of the discussion and to focus the findings around implications and next steps, and we are immensely grateful to all workshop participants for their time, energy, and ideas. However, it was possible to capture only a small portion of the marvelous ideas that surfaced across those few days. It is readily apparent that this event needs to be repeated often given the wealth of scientific opportunities that are now emerging, as reflected in this Report. Like a pebble landing in a pond, we hope the radiating energy continues to spread throughout our community.
The Report is organized into chapters on top-down causality, bottom-up emergence, and the diverse interface now forming between and connecting the two in a region we call the golden spike. Research implications and actions distilled from the Workshop discussions are provided in each chapter. We certainly anticipate other opportunities will appear with time, and we hope the identified actions will catalyze the development of a road map for future discussions and research opportunities, as well as other workshops and symposia. In the spirit in which this report was developed, we urge you to circulate it widely among your colleagues in all relevant disciplines and at professional societies and foundation meetings, and to participate in what we hope will be multiple follow-up workshops and symposia.
The Golden Spike
The term “golden spike” refers to the last spike driven into the rails connecting the Central Pacific and Union Pacific Railroads, creating the country’s First Transcontinental Railroad. Similarly, research at the intersection of top-down causality and the molecular diversity of bottom-up emergent dynamic chemical networks explores a unique space between chemical and biological evolution. Just as a pebble thrown into a pond creates ripples moving outward from the center, so alternative forms of life may emerge from the golden spike. It is even possible that there are other forms of life alongside those powered by the central dogma—what is often referred to as the shadow biosphere—at this juncture.
Although research at this juncture presents significant challenges, it also offers remarkable opportunities for alternative biochemical innovation. First, this opportunity encourages scientists to visit regions of the evolutionary landscape not previously explored through Earth’s history. Second, research findings could change what we currently think of as the pre-Darwinian threshold—before the appearance of the ribosome-—through the discovery of new signatures that emerge from dynamic chemical network research.
Top-Down Causality
Advances in genome sequencing technology have allowed the molecular blueprint of all living things to be traced back to the emergence of the ribosome. From this molecular digital-to-analog converter radiated all cellular life. But we also learned that this blueprint is both far simpler and much more complex than we ever imagined. While the number of human genes is far fewer than we expected, our knowledge of the remarkable epigenetic coupling with the environment and extensive lateral gene transfer throughout evolution has radically changed our view of molecular heredity.
To truly understand this system, the range of diverse chemistry that makes it possible, and the extent to which alternate chemistries may have been discovered and abandoned, we must now map the molecular underpinnings of life on Earth today. The environment organisms live in—either here or on another planet—affects their growth, as does the diversity of organisms living together side by side. The nature of these relationships raises questions about how the environment affects and even alters genes, how the diversity of populations of organisms influences biochemical innovation, and how such interactions among organisms influence and shape environmental dynamics. The answers to these questions will significantly impact future survival.
Bottom-Up Emergence
While the ribosome may be a pinnacle of molecular innovation, unlocking the explosion of biological diversity on Earth that is still going on, this Darwinian threshold of cellular life was itself a result of eons of chemical evolution, directed not by a set of genotypic blueprints, but rather from the inherent, self-organizing properties of dynamic chemical networks.
Recognizing the importance of chemical networks, research in this realm is taking shape through the development of new models in the laboratory. These models allow scientists to explore how separate and chemically distinct genotypic and phenotypic molecular representations emerge. This work not only extends the space of standard biochemistry, but also requires completely new formats in the realm of chemical evolution. The ultimate goal is to sort out the chemical and environmental determinants that both allow for development of autonomous chemical networks and shape their evolution into unique functional forms.
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