CHAMPAIGN, Ill. -- 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.

"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 linke
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Contact: Jim Barlow, Life Sciences Editor
jebarlow@uiuc.edu
217-333-5802
University of Illinois at Urbana-Champaign
17-Jun-2003

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