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Planctomycete bacterium's internal membranes contain nuclear pore-like structures

Gemmata obscuriglobus' pore-like structures share protein domains with eukaryotic nuclear pore complexes



IMAGE: Pore-like structures of the bacterium Gemmata obscuriglobus scattered over membrane released from lysed cells (transmission electron microscopy of a negatively stained preparation. The large type of pore-like structure has inner... view more

Credit: Sagulenko et al (2017)

A planctomycete bacterium features structures embedded in its internal membranes which resemble eukaryotic nuclear pores, according to a study published February 1, 2017 in the open-access journal PLOS ONE by Evgeny Sagulenko and a team led by John Fuerst from the University of Queensland, Australia.

Gemmata obscuriglobus and other planctomycetes are unusual bacteria in having internal membranes which split off their genetic material from the rest of the cell. This has parallels with the nucleus of a eukaryotic cell. The authors of the present study investigated the internal membranes of G. obscuriglobus in detail, using various electron microscopy methods to analyse the structures embedded in these membranes.

The researchers found that the internal membranes of G. obscuriglobus contain embedded pore-like protein complexes whose structure is similar to that of eukaryotic nuclear pores, and may be the first such structures found in bacteria. Like eukaryote nuclear pores, the bacterial structures contain a basket structure, spokes, and eight-fold rotational symmetry. Some of the proteins associated with the complexes even contain the same structural domains as eukaryote nuclear pore proteins.

It is not clear whether eukaryotic nuclear pores evolved from these similar bacterial pore-like structures or whether the two structures evolved separately, and more detailed analysis of the structures would be needed to help determine their evolutionary origin. Nonetheless, this may be the first description in bacteria of a nuclear pore-like structure, previously thought to be the sole preserve of eukaryotes.

"We have discovered structures in internal membranes of a bacterium resembling in important ways the nuclear pores of eukaryote cell nuclei, previously thought to be unique to organisms more complex than bacteria, ranging from yeast to human," says John Fuerst. "Finding nuclear pore-like structures in the bacterial species Gemmata obscuriglobus is significant for understanding how the cell nucleus and the pores embedded in its membrane envelope could have evolved, a major unsolved problem in evolutionary cell biology."


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Citation: Sagulenko E, Nouwens A, Webb RI, Green K, Yee B, Morgan G, et al. (2017) Nuclear Pore-Like Structures in a Compartmentalized Bacterium. PLoS ONE 12(2): e0169432. doi:10.1371/journal.pone.0169432

Funding: JAF was supported by Australian Research Council Discovery Project DP0881485. AMP was supported by Royal Society of New Zealand RDF-UOC1101. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing Interests: The authors have declared that no competing interests exist.

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