Nuclear Pore-Like Structures in a Compartmentalized Bacterium.

Evgeny Sagulenko,John A Fuerst,Ryan Catchpole,Anthony M Poole,Amanda Nouwens,Benjamin Yee,Kathryn Green,Uyen Thi Phuong Pham,Garry Morgan,Nicholas Chia,Richard I Webb,Andrew Leis,Stinus Lindgreen,Margaret K Butler,Kuo-Chang Lee,Dipshikha Chakravortty

doi:10.1371/journal.pone.0169432

Abstract

Planctomycetes are distinguished from other Bacteria by compartmentalization of cells via internal membranes, interpretation of which has been subject to recent debate regarding potential relations to Gram-negative cell structure. In our interpretation of the available data, the planctomycete Gemmata obscuriglobus contains a nuclear body compartment, and thus possesses a type of cell organization with parallels to the eukaryote nucleus. Here we show that pore-like structures occur in internal membranes of G.obscuriglobus and that they have elements structurally similar to eukaryote nuclear pores, including a basket, ring-spoke structure, and eight-fold rotational symmetry. Bioinformatic analysis of proteomic data reveals that some of the G. obscuriglobus proteins associated with pore-containing membranes possess structural domains found in eukaryote nuclear pore complexes. Moreover, immunogold labelling demonstrates localization of one such protein, containing a β-propeller domain, specifically to the G. obscuriglobus pore-like structures. Finding bacterial pores within internal cell membranes and with structural similarities to eukaryote nuclear pore complexes raises the dual possibilities of either hitherto undetected homology or stunning evolutionary convergence.

Highlights

A nucleus surrounded by a double membrane envelope is a universal characteristic of eukaryote cells [1] and is thought to be universally absent from the prokaryote domains Bacteria and Archaea
The nuclear pore complex and many of its component proteins appear universal among eukaryotes [3], and the Last Eukaryotic Common Ancestor already possessed a complex version of the nuclear pore complex, nuclear envelope and connected endomembrane system [4,5,6]
By whole-cell tomography and conventional transmission electron microscopy (TEM), we have previously established that the riboplasm and nucleoid compartments of G. obscuriglobus cells are bounded by membranes [7,8,9]

Summary

Introduction

A nucleus surrounded by a double membrane envelope is a universal characteristic of eukaryote cells [1] and is thought to be universally absent from the prokaryote domains Bacteria and Archaea.

Results

Conclusion