Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Organelle’s discovery challenges theory, could alter approach to disease treatment

18.06.2003


Researchers looking inside a pathogenic soil bacterium have found an organelle, a subcellular pouch, existing independently from the plasma membrane. The discovery within a prokaryotic organism challenges the theory on the origin of eukaryotic organelles and suggests a targeted approach to killing many disease-causing organisms.


Acidocalcisomes (the black spheres) as viewed in a trypanosome, a family of parasites that cause African sleeping sickness, Chagas disease and leishmaniasis and the first organisms where Docampo found this organelle. The cell is approximately 10 microns long and 4 microns wide. Courtesy of Kildare Miranda



"The organelle we found in the bacterium Agrobacterium tumefaciens is practically identical to the organelle called acidocalcisome in unicellular eukaryotes," said Roberto Docampo, a professor of veterinary pathobiology in the College of Veterinary Medicine at the University of Illinois at Urbana-Champaign.

Docampo began researching these organelles in 1994. He soon determined that a tiny granule in yeast, fungi and bacteria, thought to be for storage, was a fully operational organelle containing pyrophosphatase, a pump-like enzyme that allows proton transport. He named it an acidocalcisome for its acidic and calcium components. In 2000, he reported its existence in Plasmodium berghei, a malaria-causing eukaryotic parasite.


The newest discovery appeared in a paper published online this month by the Journal of Biological Chemistry. The paper, by Docampo and colleagues at the Center for Zoonoses Research and Laboratory of Molecular Parasitology at Illinois, will be published in a later print edition of the journal.

Agrobacterium tumefaciens is a prokaryote, a unicellular organism lacking membrane-bound nuclei. It causes crown gall disease in many broad-leaved plants but also is a favored tool for plant breeding because of its model system of DNA transfer into the hosts it invades. Samples were provided to Docampo’s team by biotechnology researcher Stephen K. Farrand, a professor of microbiology and crop sciences at Illinois.

Bacteria and other prokaryotes generally lack an endomembrane system.

Thus bacteria are presumed to lack compartments such as organelles not somehow linked to the plasma membrane ringing the organisms.

"What we describe is a discrete organelle independent of the plasma membrane," Docampo said. "It has a proton pump in its membrane, which is used to maintain its interior acidic content. This has never been described before in a bacterium."

The existence of discrete organelles is a defining component of unicellular eukaryotes, which have membrane-bound nuclei and specialized structures in their cell boundaries. The evolution of eukaryotic organelles "is a matter of extensive debate," Docampo said. The principle of endosymbiosis says that as microorganisms engulfed others, then new, membrane-surrounded organelles emerged in eukaryotes.

"It appears that this organelle has been conserved in evolution from prokaryotes to eukaryotes, since it is present in both. This argues against the belief that all eukaryotic organelles were formed when early eukaryotes swallowed prokaryotes," he said.

Using transmission electron and immunoelectron microscopy and X-ray microanalysis on the bacterium, researchers got a highly magnified and illuminated view.

They applied a fluorescent dye into the suspected organelle. They saw a membrane around it. The dye stained areas only within it, not in the cytosol. Serum containing antibodies to peptides related to pyrophosphatase unveiled this pump-like enzyme, and other staining techniques revealed high levels of polyphosphate only in the organelle.

Many parasites such as those that cause malaria, African sleeping sickness and toxoplasmosis and bacteria that contain these acidocalcisome organelles are pathogens.

Some pharmaceutical approaches have targeted pyrophosphate-related enzymes, Docampo said. "Our suggestion is that if drugs specifically targeted these organelles, you may be able to kill the entire organisms."

In addition to Docampo, other Illinois researchers were Manfredo Seufferheld, Mauricio C.F. Vieira, Felix A. Ruiz, Claudia O. Rodrigues and Silvia N.J. Moreno. The National Institutes of Health funded the research through a grant to Docampo.

Jim Barlow | UIUC
Further information:
http://www.news.uiuc.edu/scitips/03/0617organelle.html

More articles from Life Sciences:

nachricht Climate Impact Research in Hannover: Small Plants against Large Waves
17.08.2018 | Leibniz Universität Hannover

nachricht First transcription atlas of all wheat genes expands prospects for research and cultivation
17.08.2018 | Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Color effects from transparent 3D-printed nanostructures

New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference

Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...

Im Focus: Unraveling the nature of 'whistlers' from space in the lab

A new study sheds light on how ultralow frequency radio waves and plasmas interact

Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...

Im Focus: New interactive machine learning tool makes car designs more aerodynamic

Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.

When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...

Im Focus: Robots as 'pump attendants': TU Graz develops robot-controlled rapid charging system for e-vehicles

Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.

Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....

Im Focus: The “TRiC” to folding actin

Proteins must be folded correctly to fulfill their molecular functions in cells. Molecular assistants called chaperones help proteins exploit their inbuilt folding potential and reach the correct three-dimensional structure. Researchers at the Max Planck Institute of Biochemistry (MPIB) have demonstrated that actin, the most abundant protein in higher developed cells, does not have the inbuilt potential to fold and instead requires special assistance to fold into its active state. The chaperone TRiC uses a previously undescribed mechanism to perform actin folding. The study was recently published in the journal Cell.

Actin is the most abundant protein in highly developed cells and has diverse functions in processes like cell stabilization, cell division and muscle...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

LaserForum 2018 deals with 3D production of components

17.08.2018 | Event News

Within reach of the Universe

08.08.2018 | Event News

A journey through the history of microscopy – new exhibition opens at the MDC

27.07.2018 | Event News

 
Latest News

Smallest transistor worldwide switches current with a single atom in solid electrolyte

17.08.2018 | Physics and Astronomy

Robots as Tools and Partners in Rehabilitation

17.08.2018 | Information Technology

Climate Impact Research in Hannover: Small Plants against Large Waves

17.08.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>