, August 23, 2010  —  LONDON — The fear of falling may be enough to make elderly people more likely to fall, regardless of their actual risk, a new study says.

Australian and Belgian researchers followed 500 men and women, aged 70 to 90, for one year. They split the participants into various groups depending on their perceived and actual risks for falling. While most people had a fairly accurate sense of their chances of falling, about one-third either underestimated or overestimated their risk.

Among the people who were most afraid of falling, nearly 40 percent fell at least once within a year, even though they were rated to have a low actual risk of falling based on their physical health. The study was published online Friday in the medical journal, BMJ.

The authors said doctors should take patients’ fears of falling into consideration when recommending what might help in preventing future injuries. “The inclusion of psychological and cognitive factors should improve the accuracy of prediction of falls,” they wrote, suggesting therapies to ease anxiety about falling could help some people.

Falls in the elderly can be particularly serious since they are more prone to breaking bones or hips, which can leave them unable to walk.

Michelle Mitchell, a director at the British charity Age UK, said fear of falling can reduce people’s quality of life as well as lead to isolation and loneliness. The charity called for Britain to invest more in services specifically to prevent falls in the elderly.

The fungus Cladosporium fulvum in action on a tomato leaf. (Credit: Image courtesy of Wageningen University and Research Centre) (Aug. 23, 2010) — Fungal and bacterial pathogens are quite capable of infecting plants, animals and humans despite their immune systems. Fungi penetrate leafs, stalks and roots, or skin, intestines and lungs, to infect their hosts. Researchers from Wageningen UR (University & Research centre) discovered, together with Japanese colleagues, how this is possible. They found that the fungus secretes a protein that makes stray building blocks of the fungal cell wall invisible for the immune system of the plant, such that infection remains unnoticed.

They report their findings in the Aug. 20 issue of the journal Science.

Fungi prepare their attack, for instance on a tomato plant, rather well. Take for example the fungus Cladosporium fulvum that causes leaf mould on tomato plants. Once the fungus starts to infect, the tomato plant would recognize the fungus based on the presence of chitin fragments that are derived from the fungal cell wall. Chitin does not naturally occur in plants, but chitin fragments can always be found near fungi, just like cat hairs betray a cat’s presence. The tomato immune system recognizes the chitin fragments as “non-self and unwanted” and alarms the immune system to combat the infection. So far so good.

However, Cladosporium fulvum as well as nearly all other fungi carry a secret weapon. A team of researchers under the supervision of plant pathologist Bart Thomma discovered that the fungus secretes the protein Ecp6 during host attack. Ecp6 is the code name for ‘extracellular protein 6’. Ecp6 finds the chitin fragments that surround the fungus and binds them. This binding makes the chitin fragments invisible for the tomato plant, like a stealth-jet is invisible for radar, such that the immune system is not alarmed. As a result the plant gets diseased. Animal and human fungal pathogens also produce the protein, and are likely to disarm the immune system of their hosts in a similar way.

From experiments that the researchers performed to investigate the role of Ecp6, it appears that a fungus that does not produce Ecp6 is much less aggressive and less capable of causing disease in tomato plants.

Since not only Cladosporium but nearly all fungi, including pathogens of humans and animals, have Ecp6, the binding of chitin fragments appears a general strategy of fungi to evade the immune system of their hosts.

This knowledge may enable scientists to design novel methods to combat fungal diseases in agriculture (leaf mould, root and stalk rot, smut, wilt disease, apple scab, rust, tree cancer) and in health care (dandruff, athlete’s foot, candida-infections, aspergillosis, etc.).

Source:  Wageningen University and Research Centre,.

Journal Reference:

  1. Ronnie de Jonge, Peter van Esse, Anja Kombrink, Tomonori Shinya, Yoshitake Desaki, Ralph Bours, Sander van der Krol, Naoto Shibuya, Matthieu Joosten, and Bart Thomma. Conserved fungal LysM effector Ecp6 prevents chitin-triggered immunity in plants. Science, 2010; 329 (5994): 953-955 DOI: 10.1126/science.1190859

University of York, August 23, 2010  —  The nitrogen cycle is the natural process that makes nitrogen available to all organisms on earth. Scientists at the University of York have discovered that one of the world’s most common and ecologically important groups of fungi plays an unsuspected role in this key natural cycle.

Almost all plants form symbiosis with fungi in their roots, know as mycorrhizas. The commonest type of mycorrhiza is called the arbuscular mycorrhiza (AM) and involves two-thirds of plant species. Unlike most fungi, the AM fungi get their supply of sugars for energy and growth from their plant partner and not from the decomposition of organic matter. . Surprisingly, the researchers found that AM fungi thrive on decomposing organic matter and obtain large amounts of nitrogen from it. The fungus itself is much richer in N than plant roots, and calculations suggest that there is as much nitrogen in AM fungi globally as in roots. Since fungal hyphae (the threads of which the fungus is composed) are much shorter-lived than roots, this finding has implications for the speed with which nitrogen cycles in ecosystems,

The research, by Dr Angela Hodge and Professor Alastair Fitter in the Department of Biology at York was funded by the Biotechnology and Biological Sciences Research Council, is published in the latest issue of Proceedings of the National Academy of Sciences (PNAS).

Because these fungi cannot be grown in pure culture, the researchers created microcosms to isolate the fungi from plant roots and to allow them access to a patch of organic matter, and used stable isotopes to track the movement of nitrogen and carbon. Fungi that exploited decomposing organic matter were also better able to colonize a new plant. In addition, reducing the carbon supply to the fungus by shading the host plant did not diminish he fungal growth in the organic matter. Dr Hodge said: “We have known for a long time that these fungi play a central role in the phosphorus cycle; now it seems that they are equally important in the nitrogen cycle, opening the possibility of exploiting them in the development of more sustainable forms of agriculture. ”

Source:  University of York.

Journal Reference:

  1. 1.                     Hodge et al. Substantial nitrogen acquisition by arbuscular mycorrhizal fungi from organic material has implications for N cycling. Proceedings of the National Academy of Sciences, 2010; DOI: 10.1073/pnas.1005874107, July/August 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 in association with nearly all plants in nature, where they deliver essential nutrients — specifically phosphate — to plants in return for sugar. The findings are nevertheless a surprise, according to researchers reporting online on June 10th in Current Biology because there has been little evidence thus far to suggest that crop plants actually respond to the fungi.

“Global reserves of phosphate are critically low, and because the demand for phosphate goes hand in hand with human population expansion, it is predicted that there will be major shortages in the next few decades,” said Ian Sanders of the University of Lausanne in Switzerland. “Unfortunately, most of our important crop plants do not respond strongly, if at all, to inoculation with these fungi. This is especially so for rice, the most globally important food plant. There are no clear reports that rice benefits from inoculation with mycorrhizal fungi.”

That is, until now. In fact, the researchers started with a strain of mycorrhizal fungus of the species Glomus intraradices that clearly didn’t benefit rice. They then took advantage of the fungus’s unusual genetics. A single fungal filament can contain genetically distinct nuclei. Those distinct nuclei can fuse together, mixing genes up in different combinations, and fungal spores can also end up with different complements of genes, the new research shows. As such, the supposedly clonal fungi maintain a degree of genetic variation that had been overlooked.

“It turns out we can very simply manipulate their genetics to produce fungi that induce up to a five-fold growth increase in this globally important food plant,” Sanders said.

The genetic changes that the researchers produced in the fungi led to changes in the activity of important genes in the rice, they report. Those affected genes are known to be involved in establishing the mutually beneficial relationship between plant and fungus and in the transport of phosphate at the interface between fungus and plant.

Sanders emphasized that the genetic manipulation the researchers undertook didn’t involve any insertion of new genes into the fungal genome. It rather relied on the same biological processes of genetic exchange and segregation that normally take place in the fungus. “What we have done with these fungi is not much different from what plant breeders, and farmers before them, have done to improve crops,” he said. “The only difference is that the genetics of these fungi is a little bit more unusual, and no one thought it worth doing.”

On a cautionary note, Sanders did emphasize that the plants they studied were grown in a greenhouse in Switzerland under conditions that only mimicked those found in the tropics. “This is clearly not at all the same environment as a rice plant growing in a real paddy field,” he said. It remains to be seen whether the same growth benefits will apply in practice.

“However,” Sanders said, “our study clearly shows that the potential is there to manipulate the genetics of the fungus to achieve greater crop yields.”

Source:  Cell Press

Journal Reference:

  1. 1.                     Caroline Angelard, Alexandre Colard, Hélène Niculita-Hirzel, Daniel Croll, and Ian R. Sanders. Segregation in a Mycorrhizal Fungus Alters Rice Growth and Symbiosis-Specific Gene Transcription. Current Biology, June 10, 2010 DOI: 10.1016/j.cub.2010.05.031