Invisibility cloak needed for cooperation? Unusual lipopolysaccharide enables symbiosis between bacterium, fungus

Sep 07, 2010

(PhysOrg.com) -- We and all other organisms must constantly grapple with bacteria. Whether for a necessary symbiosis or an infection, carbohydrate structures on cell surfaces play an important role in the interactions between bacteria and organisms.

A team led by Antonio Molinaro at the University of Naples and Christian Hertweck at the Leibniz Institute for Natural Product Research and Infection Biology in Jena have now discovered an unusual carbohydrate structure without which the symbiosis between a bacterium and a fungus that affects rice plants is not stable. As the researchers report in the journal , the bacterium probably requires this structure as camouflage for protection against the defense mechanisms of the fungus.

In gram-negative bacteria, lipopolysaccharide (LPS) carbohydrate structures are especially important for cell-cell interactions. LPS consists of a complex chain made of various saccharide molecules and a lipid that anchors the structure in the cell membrane. “Previous studies were limited to the role of LPS in the interaction of bacteria with animals or plants,” says Hertweck. “There is thus a sizeable knowledge gap with respect to interaction with other microbes.” The team has now examined a singular symbiosis: The fungus Rhizopus microsporus, which causes rice blight, inhibits root growth in rice plants, causing the plants to die. To achieve this, the fungus needs a partner—the bacterium Burkholderia rhizoxinica. The bacteria produce toxins needed by the fungus to damage the . The nutrients released by the dead plants are then used by both symbiotic partners.

“Until now the mechanism that allows the bacteria to survive within the has remained a mystery,” says Hertweck. Now the team seems to be on the heels of a solution. “We have found an unusual , a chain of several galactose molecules, in the LPS of the bacterium,” says Herweck. “This pattern has not been seen before in this class of bacteria; however similar structures often occur in fungi.” The bacterium possibly mimics these structural elements of its host organism. The researchers infected fungi with mutated bacteria that did not contain these polysaccharides. In this case, the partners are not able establish a stable symbiosis. This becomes evident when the fungi are no longer able to produce spores.

“The special galactose sequence probably acts as a disguise for the ,” opines Hertweck. “It is possible that it is thus not recognized as foreign, which keeps it safe from the defense mechanism of the .”

Explore further: Structure of sodium channels different than previously believed

More information: Christian Hertweck, An Unusual Galactofuranose Lipopolysaccharide That Ensures the Intracellular Survival of Toxin-Producing Bacteria in Their Fungal Host, Angewandte Chemie International Edition, dx.doi.org/10.1002/anie.201003301

Related Stories

With fungi on their side, rice plants grow to be big

Jun 10, 2010

By tinkering with a type of fungus that lives in association with plant roots, researchers have found a way to increase the growth of rice by an impressive margin. The so-called mycorrhizal fungi are found ...

Farming and chemical warfare: A day in the life of an ant?

Nov 17, 2008

One of the most important developments in human civilisation was the practice of sustainable agriculture. But we were not the first - ants have been doing it for over 50 million years. Just as farming helped humans become ...

A new plant-bacterial symbiotic mechanism promising

Jul 16, 2007

The growth of most plants depends on the presence of sufficient amounts of nitrogen contained in the soil. However, a family of plants, the legumes, is partially free of this constraint thanks to its ability to live in association ...

Recommended for you

Breakthrough points to new drugs from nature

Apr 16, 2014

Researchers at Griffith University's Eskitis Institute have developed a new technique for discovering natural compounds which could form the basis of novel therapeutic drugs.

World's first successful visualisation of key coenzyme

Apr 16, 2014

Japanese researchers have successfully developed the world's first imaging method for visualising the behaviour of nicotine-adenine dinucleotide derivative (NAD(P)H), a key coenzyme, inside cells. This feat ...

User comments : 0

More news stories

Impact glass stores biodata for millions of years

(Phys.org) —Bits of plant life encapsulated in molten glass by asteroid and comet impacts millions of years ago give geologists information about climate and life forms on the ancient Earth. Scientists ...

Researchers successfully clone adult human stem cells

(Phys.org) —An international team of researchers, led by Robert Lanza, of Advanced Cell Technology, has announced that they have performed the first successful cloning of adult human skin cells into stem ...