My
#article addresses the latest scientific findings regarding the structure of the
#cellwall in
#Archaea. It also explores
#evolutionary #scenarios that led to the emergence of
#eukaryotes.
A particularly significant evolutionary achievement of eukaryotes is the possession of
#mitochondria, the cell's "power stations", which supply the cellular metabolism with free energy in the form of
#ATP.
Approximately 1.6 to 1.8 billion years ago, an event known as
#eukaryogenesis occurred. The world of living organisms, at that time confined to
#anaerobicconditions in the
#oceans, underwent a dramatic transformation within a relatively short period. This shift had profound consequences for the previously dominant unicellular organisms: the
#archaea and the
#bacteria.
The so-called
#GreatOxidationEvent
approximately 2.4 to 2.1 billion years ago pushed archaea into sediment layers where largely anaerobic conditions still prevailed. There, they coexisted with metabolically flexible
#alphaproteobacteria.
Within the Archaea, the
#Asgard archaea are the
#sistergroup to the Eukaryota. They had already lost the cell wall found in other archaea, a state that persisted in early eukaryotes. This loss of the cell wall was the prerequisite for an important case of
#endosymbiosis, specifically, the incorporation of alphaproteobacteria, the later mitochondria. It is no longer believed that true
#phagocytosis of the bacteria occurred; instead, the bacteria were initially held in place by
#armlike #projections formed from the archaea's flexible membrane. Over the course of evolution, these projections fused together, thereby enclosing the bacterium. Initially, the incorporated bacterium enabled a
#syntrophic #exchange of substances between
#host and
#endosymbiont (e.g., hydrogen transfer between the Asgard host and the alphaproteobacterium); The bacterium was able to break down organic substances much more efficiently with the help of
#oxygen.
The Asgard host provided metabolic products and was protected from direct contact with oxygen by the bacterium, which was helpful given the rising oxygen content in the water and the resulting steep physical and chemical gradients, so-called
#oxyclines.
Later, this arrangement evolved into an innovation for generating large amounts of energy.
R. Smith et al. (2026) investigated the cell wall structure of the archaeon
#Methanobrevibacter #smithii, a member of the human gut microbiome. They discovered that the cell wall contains a previously unknown sugar, which the researchers named N-acetylarmosamine (
#ArmNAc). This finding is remarkable because the prevailing scientific consensus had previously assumed the presence of the sugar building block N-acetyltalosaminuronic acid (
#TalNAc) instead. Furthermore, the researchers identified the
#enzyme #ArmA, a hydrolase that acts as
#molecularscissors to locally cleave the rigid ArmNAc sugar armor. This grants the underlying
#membrane greater mobility and
#flexibility, a crucial factor during cell division. The insights into cell envelope regulation in archaea gained through this research will also pave the way for understanding membrane flexibility in the cell-wall-lacking Asgard archaea, a factor of great significance regarding the eukaryogenesis. However, this does not directly imply that they used ArmA, but rather that
#enzymemediated #regulation of cell envelope modification is a deeply rooted archaeal trait.
©
#StefanFWirth, October 2026, Berlin
Please support my science writing efforts: ko-fi link 👇 in my first reply.
Reference:
R. Smith et al. (2026):
DOI: 10.1038/s41586-026-11028-y 👇 link in my first reply.
#Images:
1) Eukaryogenesis.
Authors H. Imachi et al. (2020), under which the Creative Commons License 4.0 international. 👇link in my first answer
2)
#Protheoarchaeum #syntrophicum, artistic recreation in plasticine.
Author Maulucioni, 2020,
under the Creative Commons Attribution-ShareAlike License 4.0 international 👇 link in my first answer