Researchers create three-dimensional model of bacterium

Aug 16, 2013

Certain bacteria can build such complex membrane structures that, in terms of complexity and dynamics, look like eukaryotes, i.e., organisms with a distinct membrane-bound nucleus. Scientists from Heidelberg University and the European Molecular Biology Laboratory (EMBL) made this discovery employing new methods in electron microscopy. The research team succeeded in building a three-dimensional model of the Gemmata obscuriglobus bacterium, including the structure of its membrane system. Their studies proved, however, that the G. obscuriglobus does not have a "true" nucleus. Despite this outlier characteristic, it remains classified as a bacterium and thus a so-called prokaryote. The results of their research were published in PloS Biology.

"Since the beginning of microscopy, cells of have been classified into one of two categories," explains Dr. Damien Devos, a researcher at the Centre for Organismal Studies (COS) at Heidelberg University. Eukaryotes "pack" their , their DNA, in an area enclosed in a membrane, the nucleus. Prokaryotes, however, which also include bacteria, do not have that type of . Several years ago, analyses using new techniques of two-dimensional imaging had suggested that the genetic material of G. obscuriglobus was surrounded by a double membrane – this and other unique characteristics of membrane structure called into question the differentiation between prokaryotes and eukaryotes.

"The possibility that a bacterium could have a structure similar to a cell nucleus threatened to unhinge one of the central assumptions of biology on which countless other analyses and interpretations were based," explains Damien Devos. To study the unique features of the in the G. obscuriglobus more closely, the Heidelberg researchers divided the bacterium into thin slices and examined them using an . The slices were used to detect the membranes, track their course throughout the entire and reconstruct their organisation on the computer. This created a virtual model of G. obscuriglobus, which enabled the researchers to visualise the membrane organisation in three-dimensional space and analyse how the membranes were structured within the cell.

The studies demonstrated that the membranes within the G. obscuriglobus are only one part of the interior membrane that is present in all bacteria and that surrounds the cytoplasm. "G. obscuriglobus also evidenced additional characteristics that are found in other bacteria," explains Damien Devos. According to the researcher, these results disprove the assumption of the existence of a bacterial cell nucleus. "The cell structure and the membranes of the Gemmata obscuriglobus are simply more complex than in 'classic' bacteria. Therefore, G. obscuriglobus does not constitute a new, separate group of organisms, and it cannot be classified a eukaryote," says Dr. Devos, who collaborated with Rachel Santarella-Mellwig of the European Molecular Biology Laboratory.

Explore further: Cells eat themselves into shape

More information: Santarella-Mellwig R, et al. (2013) Three-Dimensional Reconstruction of Bacteria with a Complex Endomembrane System, PLoS Biol 11(5): e1001565. DOI: 10.1371/journal.pbio.1001565

add to favorites email to friend print save as pdf

Related Stories

Membrane-coat proteins: Bacteria have them too

Jan 20, 2010

Although they are present almost everywhere, on land and sea, a group of related bacteria in the superphylum Planctomycetes-Verrucomicrobia-Chlamydiae, or PVC, have remained in relative obscurity ever since ...

Cells eat themselves into shape

Aug 09, 2013

The process cells use to 'swallow' up nutrients, hormones and other signals from their environment – called endocytosis – can play a crucial role in shaping the cells themselves, scientists at the European ...

Protein team produces molecular barrels

Aug 05, 2013

Research groups headed by Prof. Dr. Nikolaus Pfanner, Dr. Nils Wiedemann, and Dr. Thomas Becker from the University of Freiburg and their colleagues have demonstrated how molecular protein barrels form in ...

Recommended for you

The 'memory' of starvation is in your genes

2 hours ago

During the winter of 1944, the Nazis blocked food supplies to the western Netherlands, creating a period of widespread famine and devastation. The impact of starvation on expectant mothers produced one of the first known ...

Sugar mimics guide stem cells toward neural fate

Jul 30, 2014

Embryonic stem cells can develop into a multitude of cells types. Researchers would like to understand how to channel that development into the specific types of mature cells that make up the organs and other structures of ...

Researchers uncover secrets of internal cell fine-tuning

Jul 29, 2014

New research from scientists at the University of Kent has shown for the first time how the structures inside cells are regulated – a breakthrough that could have a major impact on cancer therapy development.

User comments : 0