Comparable system-level organization of Archaea and Eukaryotes

Area of Science:

• Evolutionary biology
• Biochemistry
• Systems biology

Background:

• The origin of biological variation is a fundamental question in evolutionary theory.
• Nucleotide and gene content analyses have advanced understanding of species relationships and life's domains.
• Comparing higher-level systemic organization offers new avenues for exploring evolutionary connections.

Purpose of the Study:

• To investigate evolutionary relationships by analyzing biochemical reaction pathways across diverse species.
• To compare the pathway-level organization of metabolic networks in Archaea and Eukaryotes.
• To understand the constraints on enzyme incorporation during the symbiotic evolution of eukaryotes.

Main Methods:

• Multivariate analyses were applied to biochemical reaction pathways.
• Biochemical pathways of 43 species were evaluated.
• Information transfer pathways and metabolic network organization were compared.

Main Results:

• A close evolutionary relationship was identified between Archaea and Eukaryotes based on information transfer pathways.
• Eukaryotic metabolic enzymes are predominantly of bacterial origin.
• Despite bacterial enzyme origins, the pathway-level organization of archaeal and eukaryotic metabolic networks is more similar.

Conclusions:

• The study suggests that the symbiotic evolution of eukaryotes involved the incorporation of bacterial metabolic enzymes.
• This incorporation was constrained by the host's (proto-archaeal) pre-existing metabolic architecture.
• Comparing systemic organization provides insights into the deep evolutionary history and relationships between major life domains.