The Origins of Cellular Life

Abstract

Understanding the origin of cellular life on Earth requires the discovery of plausible pathways for the transition from complex prebiotic chemistry to simple biology, defined as the emergence of chemical assemblies capable of Darwinian evolution. We have proposed that a simple primitive cell, or protocell, would consist of two key components: a protocell membrane that defines a spatially localized compartment, and an informational polymer that allows for the replication and inheritance of functional information. Recent studies of vesicles composed of fatty-acid membranes have shed considerable light on pathways for protocell growth and division, as well as means by which protocells could take up nutrients from their environment. Additional work with genetic polymers has provided insight into the potential for chemical genome replication and compatibility with membrane encapsulation. The integration of a dynamic fatty-acid compartment with robust, generalized genetic polymer replication would yield a laboratory model of a protocell with the potential for classical Darwinian biological evolution, and may help to evaluate potential pathways for the emergence of life on the early Earth. Here we discuss efforts to devise such an integrated protocell model.

The RNA Worlds in Context

“…Schrum et al (2010) describe progress in achieving replication of simple nucleic acid-like polymers within lipid envelopes, thereby constituting "protocells." These liposomes can grow and upon agitation can divide to give daughter protocells, carrying newly replicated nucleic acids.…”

The nature and mathematical basis for material stability in the chemical and biological worlds

“…Thus an autocatalytic network of reactions, such as the one involved in the formose reaction [36], would not satisfy this condition, as it lacks any possibility of evolving toward a state of increased DKS. Similarly, a system involving the autocatalytic production of fatty acids leading to vesicle division [37] would also be unable to satisfy this condition. But once evolvability is present within the system, such as is naturally found in template-based biopolymeric replicating systems, the DKS formulation opens up a mechanism for the stabilization of inherently less stable replicating entities.…”

Microbial diversity and the “lower-limit” problem of biodiversity

“…Some argue that such systems are still far from being alive and need many additional features to be so; others consider these systems as very close to fully living (e.g. Rasmussen et al 2003;Noireaux et al 2005;Schrum et al 2010). Probably one of the most enduring controversies on defining life concerns the status of viruses.…”