Framing major prebiotic transitions as stages of protocell development: three challenges for origins-of-life research

Abstract

Conceiving the process of biogenesis as the evolutionary development of highly dynamic and integrated protocell populations provides the most appropriate framework to address the difficult problem of how prebiotic chemistry bridged the gap to full-fledged living organisms on the early Earth. In this contribution we briefly discuss the implications of taking dynamic, functionally integrated protocell systems (rather than complex reaction networks in bulk solution, sets of artificially evolvable replicating molecules, or even these same replicating molecules encapsulated in passive compartments) as the proper units of prebiotic evolution. We highlight, in particular, how the organisational features of those chemically active and reactive protocells, at different stages of the process, would strongly influence their corresponding evolutionary capacities. As a result of our analysis, we suggest three experimental challenges aimed at constructing protocell systems made of a diversity of functionally coupled components and, thereby, at characterizing more precisely the type of prebiotic evolutionary dynamics that such protocells could engage in.

The Construction of Biological ‘Inter-Identity’ as the Outcome of a Complex Process of Protocell Development in Prebiotic Evolution

“…In any case, no origins-of-life researcher will doubt that, somehow (sooner or later, but within the actual process of biogenesis), prebiotic systems had to develop into functional reproductive protocells. Our claim, quite distinct from the still mainstream views in the field, is that this step had to take place early, so that there was sufficient time and opportunities, from that point onward, for protocell systems evolution (Piedrafita et al, 2017;Shirt-Ediss et al, 2017) to proceed. The appearance of endogenous functionalization and reproductive fission in these first protocells would not necessarily coincide (notice the different endings of the triangle peaks in Figure 2B), but they should join forces soon.…”

“Minimal metabolism”: A key concept to investigate the origins and nature of biological systems

“…6 We can say that it is a functional bootstrapping because the recurrent loop between synthesis and control (the complex interconnection between those two circular areas of each plane) is precisely what causally explains the self-maintenance of the system. In other words, our understanding of the concept of function is physiological (or "dispositional"/"organizational" [90][91][92][93] , applied, more precisely, to the context of proto-cellular development [94,59] ).…”

Femtoplankton: What’s New?

“…In the early evolutionary stages, based on the hypothesis of a prebiotic peptide/RNA world developed in [ 181 ], BMOPs/nanobes, as potential supports (inside or fixed outside) of prebiotic organic chemistry, could have paved the way for the formation of primitive elements (organic molecules). The evolution of a procell towards the first protocell could have been achieved after encapsulation and compartmentalization of the primitive elements into fatty acids vesicles prior to evolution by unregulated and error-prone way division, depending on environmental conditions [ 47 , 182 ]. The complexification of the biochemical (metabolic) and replicative systems, as well as of the membrane/cell walls, during the following protocell stages would have led to divisions more independent of environmental conditions and to the initiation of the cellular and viral world [ 94 , 182 ].…”

“…The evolution of a procell toward the first protocell can be achieved after encapsulation and compartmentalization of the primitive elements into fatty acid vesicles prior to evolution by unregulated and error-prone way division, depending on environmental conditions [ 47 , 182 ]. Complexification of biochemical (metabolic) and replicative systems, as well as membrane/cell walls, during the protocell stages has led to divisions that are more independent of environmental conditions [ 182 ] and to the initiation of the cellular and viral world [ 94 ]. The emergence of Candidate Phyla Radiation/Diapherotrites Parvarchaeota Aenigmarchaeota Nanoarchaeota Nanohaloarchaeota (CPR/DPANN) from protocell or prokaryotic communities is adapted from [ 165 ].…”