Pores found in 'platypus of microbiology' bacterium push boundaries of evolution 1
( Or rather it falsfies Darwin's idea once again ? - - but but -- that can't be, can it ??!! )
A bacterium dubbed the "platypus of microbiology" is even stranger than first thought, with the discovery it contains structures normally only found in more complex cells.
Bacterium Gemmata obscuriglobus originally found in Queensland in 1984
Closer inspection of its structure reveals it is the most complex bacterium ever discovered
Finding sheds light on a major problem in evolutionary cell biology
The find, by an international team led by University of Queensland researcher Emeritus Professor John Fuerst, adds to the debate about how complex cells evolved, and casts doubt on long-held theories of evolution.
According to the dominant theory, there are three domains of life: bacteria and archaea, which are single-celled organisms without a nucleus, and eukaryotes, organisms that include everything from yeast to us.
However, the bacterium Gemmata obscuriglobus has been described as the "platypus of microbiology" because it appears to defy this theory by containing features associated with eukaryotes.
These include a membrane-bounded nucleus, the ability to transport molecules such as proteins into the cell, and its ability to reproduce by a unique way of budding.
Now Professor Fuerst and his team have discovered G. obscuriglobus has pore-like structures in its internal membrane that have elements structurally similar to eukaryote nuclear pores, which are found in the membrane surrounding the nucleus.
"This is a remarkable evolutionary finding, since most bacteria do not possess these structures," Professor Fuerst said.
He said nuclear pore complexes were important in transporting molecules between the nucleus containing the DNA and the rest of the cell contents in eukaryote organisms.
"They are dotted over the surface of the membranes separating the nucleus from the rest of the cell and enable communication between the nucleus and other parts of the cell," he said.
"Like the membrane-bounded nucleus, nuclear pore complexes had been thought to be restricted to eukaryotes."
Asgard archaea illuminate the origin of eukaryotic cellular complexity 2
The origin and cellular complexity of eukaryotes represent a major enigma in biology. Current data support scenarios in which an archaeal host cell and an alphaproteobacterial (mitochondrial) endosymbiont merged together, resulting in the first eukaryotic cell. The host cell is related to Lokiarchaeota, an archaeal phylum with many eukaryotic features. The emergence of the structural complexity that characterizes eukaryotic cells remains unclear. Here we describe the ‘Asgard’ superphylum, a group of uncultivated archaea that, as well as Lokiarchaeota, includes Thor-, Odin- and Heimdallarchaeota. Asgard archaea affiliate with eukaryotes in phylogenomic analyses, and their genomes are enriched for proteins formerly considered specific to eukaryotes. Notably, thorarchaeal genomes encode several homologues of eukaryotic membrane-trafficking machinery components, including Sec23/24 and TRAPP domains. Furthermore, we identify thorarchaeal proteins with similar features to eukaryotic coat proteins involved in vesicle biogenesis. Our results
expand the known repertoire of ‘eukaryote-specific’ proteins in Archaea, indicating that the archaeal host cell already contained many key components that govern eukaryotic cellular complexity.