Research throws new light on evolution of bacteria
Researchers in Germany have discovered that a relatively obscure group of related bacteria possesses proteins that were previously thought to exist only in eukaryotes (organisms that have a nucleus). The results of the study, funded in part by the EU, could lead to new model organisms and help biologists obtain a clearer picture of the evolution of eukaryotic cells in the human body. The findings are published in the journal PLoS (Public Library of Science) Biology. Despite their omnipresence, the bacteria, called superphylum Planctomycetes-Verrucomicrobia-Chlamydiae (PVC), have not received much attention since they were discovered 10 years ago. The research team at the European Molecular Biology Laboratory (EMBL) in Heidelberg, Germany is the first to provide molecular evidence that the coat proteins that shape the eukaryotic endomembrane system are also found in prokaryotes (organisms that lack a nucleus). The research study formed part of the 3D-Repertoire ('A multidisciplinary approach to determine the structures of protein complexes in a model organism') project, funded at EUR 13 million under the 'Life sciences, genomics and biotechnology for health' Thematic area of the EU's Sixth Framework Programme (FP6). Using a combination of bioinformatics, molecular biology and electron microscopy, the team discovered that membrane-coat proteins also exist in the PVC group but not in any other bacteria in association with the membranes of subcellular compartments. Scientists previously believed that both membrane-bound compartments and membrane-coat proteins were only found in eukaryotic cells, but the EMBL research team's discovery of the membrane-bound compartments in the PVC bacteria will lead to new research models. The endomembrane system of a eukaryote consists of a network of membrane-bound compartments that both transport and store material in the cell. The compartments include organelles (organs inside a cell that have highly specialised functions). These organelles include the endoplasmic reticulum and the Golgi complex, both of which are responsible, among other functions, for synthesising and transporting proteins. The organelles exchange fragments of membrane with each other by forming and absorbing vesicles (small sacs enclosed in membrane that store and transport substances within a cell). 'Our findings provide unexpected clues as to how the endomembrane system of eukaryotes evolved,' said research leader Dr Damien Devos from EMBL. 'Since they are relatively simple cells, these bacteria could be used as model organisms for studying how this system works.'
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