Picky Plants: Do They "Choose" The Best Fungal Partner?
ScienceDaily (Aug. 9, 2001) — MADISON, Wis. --- Every time we make a choice, whether between job offers in two different cities or about what to have for dinner, evaluating the costs and benefits of each option is part of the process. Researchers at the University of Michigan are finding that the ability to actively select one option over another may no longer be reserved for higher animals; in fact, plants may make choices too.
Many plants form partnerships with fungi that live in the soil. Attached to the plant's roots, the fungus provides the plant with nutrients needed for growth---usually phosphorous—and the plant provides the fungus with something it needs, usually carbon. Many plants show increased growth when they team up with a fungus, but all fungi are not created equal. Depending on the environment, one fungus may cost the plant more or less carbon in exchange for the nutrients the fungus makes available to the plant.
And according to a paper to be presented at the annual meeting of the Ecological Society of America on Aug. 8 by U-M doctoral student Miroslav Kummel, "plants may be actively 'choosing' the species of fungus that supports the highest growth for the plant."
Depending on environmental factors such as soil type or amount of light, fungi differ in their effects on plant growth, and a plant living in the shade may be better off with a different fungus than a plant living in the sun. "Of course this is the result of long-term selection," says Deborah Goldberg, a professor of ecology and evolutionary biology and one of Kummel's faculty advisers, "but the consequences are the same as if it were a cognitive choice, and that's pretty cool."
Kummel looked at the distribution pattern of different types of fungi growing on balsam fir seedlings in an area with light conditions ranging from full sun to full shade. He found that a fir seedling living in the shade associates with a different fungus than a fir seedling living in the sun, and that it teams up with the fungus that "costs" the least, while still benefiting the plant.
The mechanism by which the plant "chooses" the fungus is not yet known. It could result from the plant selectively aborting roots that associate with the more "expensive" fungus or from selective growth of new root tips. By isolating pure cultures of different fungi to more closely examine the exchange of nutrients between plant and fungus, Kummel hopes to unravel this mechanism. These experiments are in progress. Ultimately, Kummel's work could have implications for the timber industry, as many of our pulp crops and commercial hardwoods also form associations with fungi.
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Adapted from materials provided by University Of Michigan.
Sunday, June 29, 2008
Plant-Fungal Symbiosis Found In High-Heat Extreme Environment
Plant-Fungal Symbiosis Found In High-Heat Extreme Environment
ScienceDaily (Nov. 27, 2002) — ARLINGTON, Va. -- Researchers examining plants growing in the geothermal soils of Yellowstone National Park and Lassen Volcanic National Park have found evidence of symbiosis between fungi and plants that may hold clues to how plants adapt to and tolerate extreme environments.
The research was funded in part through the National Science Foundation's (NSF) Microbial Observatories Program and published in the Nov. 22 issue of the journal Science.
Biologists Regina Redman of the University of Washington and Joan Henson of Montana State University and their colleagues examined 200 samples of Dichanthelium lanuginosum, also called "Geyser's Dichanthelium," for fungal colonization. They found what may be a new species of the fungus Curvularia that survives only in temperatures greater than 98 degrees when it associates with plants.
The researchers suggest that thermotolerance may occur through symbiotic mechanisms like heat dissipation by pigment, such as melanin, or the activation of a "biological trigger" that tells the plant to react to temperature changes more rapidly or strongly than plants that lack the fungus.
The researchers grew sample plants with and without the symbiotic fungus in a laboratory and heated the soil to test thermal resistance. The plants without the fungus shriveled at 122 degrees, whereas those plants with the fungus tolerated the heat for three days. The plants were also subjected to intermittent temperatures as high as 149 degrees. The fungus-free plants died, but the fungus-bearing plants survived for 10 days.
The researchers also demonstrated that the plants provide thermal protection to the fungus by isolating it in plant roots that had a field soil temperature of 113 degrees.
"Scientific understanding of how life can thrive in such extreme environments is at its infancy," said Microbiologist Matt Kane, NSF's Microbial Observatories Program Director. "Research funded by NSF's Microbial Observatories Program is demonstrating that when you look in interesting places, you discovery interesting life forms and interrelationships, such as these fungi and their plant partners."
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Adapted from materials provided by National Science Foundation.
ScienceDaily (Nov. 27, 2002) — ARLINGTON, Va. -- Researchers examining plants growing in the geothermal soils of Yellowstone National Park and Lassen Volcanic National Park have found evidence of symbiosis between fungi and plants that may hold clues to how plants adapt to and tolerate extreme environments.
The research was funded in part through the National Science Foundation's (NSF) Microbial Observatories Program and published in the Nov. 22 issue of the journal Science.
Biologists Regina Redman of the University of Washington and Joan Henson of Montana State University and their colleagues examined 200 samples of Dichanthelium lanuginosum, also called "Geyser's Dichanthelium," for fungal colonization. They found what may be a new species of the fungus Curvularia that survives only in temperatures greater than 98 degrees when it associates with plants.
The researchers suggest that thermotolerance may occur through symbiotic mechanisms like heat dissipation by pigment, such as melanin, or the activation of a "biological trigger" that tells the plant to react to temperature changes more rapidly or strongly than plants that lack the fungus.
The researchers grew sample plants with and without the symbiotic fungus in a laboratory and heated the soil to test thermal resistance. The plants without the fungus shriveled at 122 degrees, whereas those plants with the fungus tolerated the heat for three days. The plants were also subjected to intermittent temperatures as high as 149 degrees. The fungus-free plants died, but the fungus-bearing plants survived for 10 days.
The researchers also demonstrated that the plants provide thermal protection to the fungus by isolating it in plant roots that had a field soil temperature of 113 degrees.
"Scientific understanding of how life can thrive in such extreme environments is at its infancy," said Microbiologist Matt Kane, NSF's Microbial Observatories Program Director. "Research funded by NSF's Microbial Observatories Program is demonstrating that when you look in interesting places, you discovery interesting life forms and interrelationships, such as these fungi and their plant partners."
--------------------------------------------------------------------------------
Adapted from materials provided by National Science Foundation.
Enzyme Revealed That Is Key To Fungus's Ability To Breach Immune System
Enzyme Revealed That Is Key To Fungus's Ability To Breach Immune System
ScienceDaily (Nov. 13, 2003) — DURHAM, N.C. – A newly discovered mechanism by which an infectious fungus evades the immune system could lead to novel methods to fight the fungus and other disease-causing microbes, according to Howard Hughes Medical Institute investigators at Duke University Medical Center.
Disruption of a key enzyme in the fungus Cryptococcus neoformans – a common cause of infection of the central nervous system in patients such as organ transplant recipients who lack a functioning immune system -- led to a significant loss of fungal virulence in mice, the team found. That loss of virulence stemmed from the fungus's inability to launch a counterattack against components of the innate immune system, the body's first line of defense against infection, the study showed.
The Duke-based team -- led by HHMI geneticist Joseph Heitman, M.D., director of Duke's Center for Microbial Pathogenesis, and HHMI biochemist Jonathan Stamler, M.D. -- reported their findings in the Nov. 11, 2003, issue of Current Biology. The work was funded by the National Institutes of Allergy and Infectious Diseases and the Burroughs Wellcome Fund.
The "fungal defense" enzyme, called flavohemoglobin, is prevalent among many bacterial and fungal pathogens, Heitman said, which suggests that the findings in Cryptococcus are likely relevant to other infectious microbes. New drugs that target these enzymes might therefore represent effective treatments for a wide range of infectious diseases, he said.
The human immune system uses a two-pronged mechanism to fight infection: a rapid innate response and a slower adaptive response that depends on the production of antibodies. Key components of the innate immune system are "search-and-destroy" cells called macrophages that engulf and kill invading pathogens. Macrophages kill infectious microbes using a combination of oxidants, including hydrogen peroxide, nitric oxide and related molecules.
"The body must rely on macrophages of the innate immune system to protect itself before the adaptive immune system can respond to invasion," Heitman said. "While much is known about how pathogens defend themselves against hydrogen peroxide produced by the macrophages, this study is the first biologically relevant test of what microbes do to counteract nitric oxide and promote infection."
The researchers found that a mutant C. neoformans strain lacking the flavohemoglobin enzyme failed to break down nitric oxide in laboratory cultures. Fungus with the enzyme deficiency also ceased to grow when in the presence of nitric oxide, whereas ordinary fungus survived normally.
Mice infected with the flavohemoglobin-deficient C. neoformans survived for five days longer than those infected with the normally virulent strain. In contrast, the normal and mutant fungal strains were equally virulent in mice whose immune cells could not produce nitric oxide, the team reported.
The mutant fungus also failed to grow normally in laboratory dishes containing macrophage cells, further implicating the innate immune system in the loss of virulence exhibited by fungi lacking flavohemoglobin.
The team discovered a second enzyme, known as GSNO reductase, which also plays a role in defending the fungus against nitric oxide-related molecules produced by macrophages. Mutant fungal strains deficient in both enzymes were more severely impaired than those lacking flavohemoglobin only.
"By disabling either the fungal nitric oxide defense system or the immune system's ability to produce nitric oxide, we were able to tip the balance one way or the other – in favor of the fungal infection or the host," Heitman said. "That raises the possibility that we could treat infectious disease with drugs that either inhibit fungal defense enzymes or increase the innate immune system's ability to mount a nitrosative attack."
Collaborators on the study include Marisol de Jesus-Berrios, Ph.D., Gary Cox, M.D., Limin Liu, Ph.D., and Jesse Nussbaum, all of Duke.
--------------------------------------------------------------------------------
Adapted from materials provided by Duke University Medical Center.
ScienceDaily (Nov. 13, 2003) — DURHAM, N.C. – A newly discovered mechanism by which an infectious fungus evades the immune system could lead to novel methods to fight the fungus and other disease-causing microbes, according to Howard Hughes Medical Institute investigators at Duke University Medical Center.
Disruption of a key enzyme in the fungus Cryptococcus neoformans – a common cause of infection of the central nervous system in patients such as organ transplant recipients who lack a functioning immune system -- led to a significant loss of fungal virulence in mice, the team found. That loss of virulence stemmed from the fungus's inability to launch a counterattack against components of the innate immune system, the body's first line of defense against infection, the study showed.
The Duke-based team -- led by HHMI geneticist Joseph Heitman, M.D., director of Duke's Center for Microbial Pathogenesis, and HHMI biochemist Jonathan Stamler, M.D. -- reported their findings in the Nov. 11, 2003, issue of Current Biology. The work was funded by the National Institutes of Allergy and Infectious Diseases and the Burroughs Wellcome Fund.
The "fungal defense" enzyme, called flavohemoglobin, is prevalent among many bacterial and fungal pathogens, Heitman said, which suggests that the findings in Cryptococcus are likely relevant to other infectious microbes. New drugs that target these enzymes might therefore represent effective treatments for a wide range of infectious diseases, he said.
The human immune system uses a two-pronged mechanism to fight infection: a rapid innate response and a slower adaptive response that depends on the production of antibodies. Key components of the innate immune system are "search-and-destroy" cells called macrophages that engulf and kill invading pathogens. Macrophages kill infectious microbes using a combination of oxidants, including hydrogen peroxide, nitric oxide and related molecules.
"The body must rely on macrophages of the innate immune system to protect itself before the adaptive immune system can respond to invasion," Heitman said. "While much is known about how pathogens defend themselves against hydrogen peroxide produced by the macrophages, this study is the first biologically relevant test of what microbes do to counteract nitric oxide and promote infection."
The researchers found that a mutant C. neoformans strain lacking the flavohemoglobin enzyme failed to break down nitric oxide in laboratory cultures. Fungus with the enzyme deficiency also ceased to grow when in the presence of nitric oxide, whereas ordinary fungus survived normally.
Mice infected with the flavohemoglobin-deficient C. neoformans survived for five days longer than those infected with the normally virulent strain. In contrast, the normal and mutant fungal strains were equally virulent in mice whose immune cells could not produce nitric oxide, the team reported.
The mutant fungus also failed to grow normally in laboratory dishes containing macrophage cells, further implicating the innate immune system in the loss of virulence exhibited by fungi lacking flavohemoglobin.
The team discovered a second enzyme, known as GSNO reductase, which also plays a role in defending the fungus against nitric oxide-related molecules produced by macrophages. Mutant fungal strains deficient in both enzymes were more severely impaired than those lacking flavohemoglobin only.
"By disabling either the fungal nitric oxide defense system or the immune system's ability to produce nitric oxide, we were able to tip the balance one way or the other – in favor of the fungal infection or the host," Heitman said. "That raises the possibility that we could treat infectious disease with drugs that either inhibit fungal defense enzymes or increase the innate immune system's ability to mount a nitrosative attack."
Collaborators on the study include Marisol de Jesus-Berrios, Ph.D., Gary Cox, M.D., Limin Liu, Ph.D., and Jesse Nussbaum, all of Duke.
--------------------------------------------------------------------------------
Adapted from materials provided by Duke University Medical Center.
Efficient Consumption Of Copper Allows Fungus To Infect The Brain
Efficient Consumption Of Copper Allows Fungus To Infect The Brain
ScienceDaily (Feb. 9, 2007) — Infection with the fungus Cryptococcus neoformans is a problem for individuals whose immune system is compromised (for example individuals with HIV and individuals who are taking chemotherapeutics to treat cancer). It can cause either cryptococcal pneumonia or, more seriously, meningoencephalitis.
In a study that appears online on February 8 in advance of publication in the March print issue of the Journal of Clinical Investigation, researchers from the University of Illinois at Chicago show that in mice, the infecting fungus must be adapted to grow in the presence of low levels of copper if it is to efficiently infect the brain and cause meningoencephalitis.
Peter Williamson and colleagues showed that C. neoformans lacking a protein that is essential for it to take up copper from its environment (Cuf1) are impaired in their ability to infect the brain and cause fatal meningoencephalitis.
By contrast, these mutant C. neoformans infect the lung as efficiently as C. neoformans expressing Cuf1. Consistent with this, bacteria expressing high levels of a protein controlled by Cuf1 (Ctr4) were found in the brain of mice and humans infected with C. neoformans.
This study indicates that one factor that can limit the growth of C. neoformans in the brain of mice and humans is low levels of copper, but that this is not a factor limiting growth in the lung. The authors therefore suggest that determining the level of Ctr4 expressed by the C. neoformans infecting an individual might help determine that individual’s risk of developing meningoencephalitis.
--------------------------------------------------------------------------------
Adapted from materials provided by Journal of Clinical Investigation, via EurekAlert!, a service of AAAS.
ScienceDaily (Feb. 9, 2007) — Infection with the fungus Cryptococcus neoformans is a problem for individuals whose immune system is compromised (for example individuals with HIV and individuals who are taking chemotherapeutics to treat cancer). It can cause either cryptococcal pneumonia or, more seriously, meningoencephalitis.
In a study that appears online on February 8 in advance of publication in the March print issue of the Journal of Clinical Investigation, researchers from the University of Illinois at Chicago show that in mice, the infecting fungus must be adapted to grow in the presence of low levels of copper if it is to efficiently infect the brain and cause meningoencephalitis.
Peter Williamson and colleagues showed that C. neoformans lacking a protein that is essential for it to take up copper from its environment (Cuf1) are impaired in their ability to infect the brain and cause fatal meningoencephalitis.
By contrast, these mutant C. neoformans infect the lung as efficiently as C. neoformans expressing Cuf1. Consistent with this, bacteria expressing high levels of a protein controlled by Cuf1 (Ctr4) were found in the brain of mice and humans infected with C. neoformans.
This study indicates that one factor that can limit the growth of C. neoformans in the brain of mice and humans is low levels of copper, but that this is not a factor limiting growth in the lung. The authors therefore suggest that determining the level of Ctr4 expressed by the C. neoformans infecting an individual might help determine that individual’s risk of developing meningoencephalitis.
--------------------------------------------------------------------------------
Adapted from materials provided by Journal of Clinical Investigation, via EurekAlert!, a service of AAAS.
Taking The Fungal Route Through The Soil
Taking The Fungal Route Through The Soil
ScienceDaily (Feb. 21, 2007) — Fungal hyphae play a greater role in the spread of bacteria in the soil than was previously suspected. This is the finding reported by scientists from the Helmholtz Centre for Environmental Research (UFZ) in the scientific journal Environmental Science & Technology. For the first time, scientists have been able to prove that bacteria are able to travel through the soil on the mucous membrane of living fungi.
The experiments could help speed up the remediation of contaminated land using bacteria that break down harmful substances. Air and a lack of moisture create a barrier to the mobility of bacteria in the soil, preventing them from spreading and delaying the breakdown of pollutants.
Everything is just a question of contacts
It looks like a giant green ball of wool. With a bit of imagination the photo could also be likened to a huge motorway interchange with countless roads and junctions passing over and under each other on different levels. But what Leipzig-based microbiologist Dr Lukas Y. Wick is observing so intently on his screen is in fact a photograph of a mycelium taken with a confocal laser scanning microscope. The thread-like hyphae have a diameter of just 10 micrometres – one-seventh of the diameter of a human hair.
Nevertheless, fungi are some of the world’s greatest biomass producers. A single gram of field soil can contain up to 100 metres of mycelium. Wick’s actual research objects are much smaller still. He is interested in soil bacteria. Bacteria can weaken the human organism, but they can also be useful, e.g. by breaking down pollutants.
“For the bacterium a harmful substance is not harmful,” explains Wick. “It simply breaks down the carbon compounds, producing the energy and substances that it needs to live.” But before it can do this it has to get at its ‘food’. Air and lack of moisture present insurmountable obstacles. “This is why certain pollutants are broken down so slowly in the soil. Often it is not a lack of biochemical capacity, but rather a lack of contacts.” The scientists at the UFZ are therefore studying the paths followed by the bacteria.
Probably the world’s largest motorway network
Mycelia appear to act as a kind of underground highway for bacteria. This is the conclusion reached by Lukas Wick and his team. In the laboratory experiment they succeeded in demonstrating that the bacteria move through the soil on the mycelium. The ingredients: one pollutant, separating layers made of glass pellets, uncontaminated soil and a bacterium called Pseudomonas putida. The bacteria have to fight their way through all these layers to reach the phenanthrene, their ‘food’. This polycyclic aromatic hydrocarbon is a widespread pollutant produced during every combustion process: at petrol stations, in car exhausts, during forest fires, in cigarette smoke and in old municipal gas works.
“We deliberately make the bacteria work their way upwards against gravity so that people can’t say there could be a small amount of water trickling down and carrying the bacteria with it,” says Wick. “We have tried to rule out any doubts and objections from potential critics.” The bacteria made it to the top only in places where there was a mycelium running through the soil. In the identical parallel experiment without a mycelium the bacteria were unable to surmount the barriers. “With this paper we have shown that there is an infrastructure.”
Just follow your nose
The bacteria in this laboratory experiment are so-called chemotactic bacteria. This means that they measure the concentration of their ‘target chemical’ and then move towards where the concentration is higher – as if on autopilot.
“A bacterium is not a stupid creature – it has adapted to its environment and goes where there is food.” Only one type of bacteria was used in the model experiment. In nature, however, there are countless different bacteria, which gives rise to new questions: for which of them is it an advantage to be mobile and for which is it not? It will, therefore, be some time before the processes in the soil are fully understood.
The future aim of the Helmholtz researchers is to model microbial landscapes and to investigate what happens under the influence of different factors. For this they will make use of a tool that has already helped to predict the spread of rabies and the spread of resettled animal species – ecological modelling, which in future will also be able to provide forecasts about the spread of bacteria. This knowledge will make it easier to remediate contaminated soil, perhaps making the ‘fungal highway’ not only the largest in the world, but also the only one to help return nature to its original state.
--------------------------------------------------------------------------------
Adapted from materials provided by Helmholtz Centre For Environmental Research - UFZ.
ScienceDaily (Feb. 21, 2007) — Fungal hyphae play a greater role in the spread of bacteria in the soil than was previously suspected. This is the finding reported by scientists from the Helmholtz Centre for Environmental Research (UFZ) in the scientific journal Environmental Science & Technology. For the first time, scientists have been able to prove that bacteria are able to travel through the soil on the mucous membrane of living fungi.
The experiments could help speed up the remediation of contaminated land using bacteria that break down harmful substances. Air and a lack of moisture create a barrier to the mobility of bacteria in the soil, preventing them from spreading and delaying the breakdown of pollutants.
Everything is just a question of contacts
It looks like a giant green ball of wool. With a bit of imagination the photo could also be likened to a huge motorway interchange with countless roads and junctions passing over and under each other on different levels. But what Leipzig-based microbiologist Dr Lukas Y. Wick is observing so intently on his screen is in fact a photograph of a mycelium taken with a confocal laser scanning microscope. The thread-like hyphae have a diameter of just 10 micrometres – one-seventh of the diameter of a human hair.
Nevertheless, fungi are some of the world’s greatest biomass producers. A single gram of field soil can contain up to 100 metres of mycelium. Wick’s actual research objects are much smaller still. He is interested in soil bacteria. Bacteria can weaken the human organism, but they can also be useful, e.g. by breaking down pollutants.
“For the bacterium a harmful substance is not harmful,” explains Wick. “It simply breaks down the carbon compounds, producing the energy and substances that it needs to live.” But before it can do this it has to get at its ‘food’. Air and lack of moisture present insurmountable obstacles. “This is why certain pollutants are broken down so slowly in the soil. Often it is not a lack of biochemical capacity, but rather a lack of contacts.” The scientists at the UFZ are therefore studying the paths followed by the bacteria.
Probably the world’s largest motorway network
Mycelia appear to act as a kind of underground highway for bacteria. This is the conclusion reached by Lukas Wick and his team. In the laboratory experiment they succeeded in demonstrating that the bacteria move through the soil on the mycelium. The ingredients: one pollutant, separating layers made of glass pellets, uncontaminated soil and a bacterium called Pseudomonas putida. The bacteria have to fight their way through all these layers to reach the phenanthrene, their ‘food’. This polycyclic aromatic hydrocarbon is a widespread pollutant produced during every combustion process: at petrol stations, in car exhausts, during forest fires, in cigarette smoke and in old municipal gas works.
“We deliberately make the bacteria work their way upwards against gravity so that people can’t say there could be a small amount of water trickling down and carrying the bacteria with it,” says Wick. “We have tried to rule out any doubts and objections from potential critics.” The bacteria made it to the top only in places where there was a mycelium running through the soil. In the identical parallel experiment without a mycelium the bacteria were unable to surmount the barriers. “With this paper we have shown that there is an infrastructure.”
Just follow your nose
The bacteria in this laboratory experiment are so-called chemotactic bacteria. This means that they measure the concentration of their ‘target chemical’ and then move towards where the concentration is higher – as if on autopilot.
“A bacterium is not a stupid creature – it has adapted to its environment and goes where there is food.” Only one type of bacteria was used in the model experiment. In nature, however, there are countless different bacteria, which gives rise to new questions: for which of them is it an advantage to be mobile and for which is it not? It will, therefore, be some time before the processes in the soil are fully understood.
The future aim of the Helmholtz researchers is to model microbial landscapes and to investigate what happens under the influence of different factors. For this they will make use of a tool that has already helped to predict the spread of rabies and the spread of resettled animal species – ecological modelling, which in future will also be able to provide forecasts about the spread of bacteria. This knowledge will make it easier to remediate contaminated soil, perhaps making the ‘fungal highway’ not only the largest in the world, but also the only one to help return nature to its original state.
--------------------------------------------------------------------------------
Adapted from materials provided by Helmholtz Centre For Environmental Research - UFZ.
Mutualism: Fungus Found That Needs Bacteria In Cytoplasm To Reproduce
Mutualism: Fungus Found That Needs Bacteria In Cytoplasm To Reproduce
ScienceDaily (Apr. 6, 2007) — Endosymbiotic relationships--in which one organism lives within another--are striking examples of mutualism, and can often significantly shape the biology of the participant species.
In new findings that highlight the extent to which a host organism can become dependent on its internal symbiont, researchers have identified a case in which the reproduction of a fungus has become dependent on bacteria that live within its cytoplasm. The findings, which appear online in the journal Current Biology on April 5th, are reported by Laila Partida and Christian Hertweck from the Leibniz Institute for Natural Product Research and Infection Biology in Jena, Germany.
The particular partnership under study is the symbiosis of the fungus Rhizopus microsporus and Burkholderia bacteria that live within its cells. The two species effectively team up to break down young rice plants for their nutrients, causing a plant disease known as rice seedling blight. Past work from the research group had revealed that the Burkholderia bacteria play a critical role in the virulence of the fungus against rice seedlings: The bacteria produce a plant poison known as rhizoxin, which has been shown to be the causative agent in rice seedling blight.
The researchers now report a second, striking benefit conferred on the fungus by its intracellular symbiont. When the bacteria are eliminated from the fungus with antibiotic treatment, the fungal cells are no longer able to form spores, suggesting that the bacterial symbiont is in fact required for this mode of fungal reproduction. Spore formation in fungi is a universal process that allows the rapid distribution of fungal cells. The new findings appear to represent the first known case in which spore formation--also known as vegetative reproduction--depends on the presence of another organism.
The researchers found that when both organisms were brought together to re-establish the symbiosis, sporulation was restored in the fungus.
In collaboration with researchers at the Leibniz Institute for Age Research, Jena, the team also made progress in understanding how the endosymbiotic bacteria influence reproduction by their host. Using a laser gun to introduce Burkholderia that had been specially labeled with a marker known as green fluorescent protein, the researchers were able to detect the bacteria within both mycelium--the vegetative portion of the fungus--and fungal spores.
On the basis of their findings, the authors conclude that the symbiont-dependent spore formation they observe is a means to maintain the symbiosis between the two species. Although the fungus has lost control over its reproduction, the endofungal bacteria in return provide a highly potent toxin for defending the habitat and accessing nutrients from decaying plants.
Partida-Martinez et al.: "Endosymbiont-Dependent Host Reproduction Maintains Bacterial-Fungal Mutualism." Publishing in Current Biology 17, 1--5, May 1, 2007. DOI 10.1016/j.cub.2007.03.039.
--------------------------------------------------------------------------------
Adapted from materials provided by Cell Press, via EurekAlert!, a service of AAAS.
ScienceDaily (Apr. 6, 2007) — Endosymbiotic relationships--in which one organism lives within another--are striking examples of mutualism, and can often significantly shape the biology of the participant species.
In new findings that highlight the extent to which a host organism can become dependent on its internal symbiont, researchers have identified a case in which the reproduction of a fungus has become dependent on bacteria that live within its cytoplasm. The findings, which appear online in the journal Current Biology on April 5th, are reported by Laila Partida and Christian Hertweck from the Leibniz Institute for Natural Product Research and Infection Biology in Jena, Germany.
The particular partnership under study is the symbiosis of the fungus Rhizopus microsporus and Burkholderia bacteria that live within its cells. The two species effectively team up to break down young rice plants for their nutrients, causing a plant disease known as rice seedling blight. Past work from the research group had revealed that the Burkholderia bacteria play a critical role in the virulence of the fungus against rice seedlings: The bacteria produce a plant poison known as rhizoxin, which has been shown to be the causative agent in rice seedling blight.
The researchers now report a second, striking benefit conferred on the fungus by its intracellular symbiont. When the bacteria are eliminated from the fungus with antibiotic treatment, the fungal cells are no longer able to form spores, suggesting that the bacterial symbiont is in fact required for this mode of fungal reproduction. Spore formation in fungi is a universal process that allows the rapid distribution of fungal cells. The new findings appear to represent the first known case in which spore formation--also known as vegetative reproduction--depends on the presence of another organism.
The researchers found that when both organisms were brought together to re-establish the symbiosis, sporulation was restored in the fungus.
In collaboration with researchers at the Leibniz Institute for Age Research, Jena, the team also made progress in understanding how the endosymbiotic bacteria influence reproduction by their host. Using a laser gun to introduce Burkholderia that had been specially labeled with a marker known as green fluorescent protein, the researchers were able to detect the bacteria within both mycelium--the vegetative portion of the fungus--and fungal spores.
On the basis of their findings, the authors conclude that the symbiont-dependent spore formation they observe is a means to maintain the symbiosis between the two species. Although the fungus has lost control over its reproduction, the endofungal bacteria in return provide a highly potent toxin for defending the habitat and accessing nutrients from decaying plants.
Partida-Martinez et al.: "Endosymbiont-Dependent Host Reproduction Maintains Bacterial-Fungal Mutualism." Publishing in Current Biology 17, 1--5, May 1, 2007. DOI 10.1016/j.cub.2007.03.039.
--------------------------------------------------------------------------------
Adapted from materials provided by Cell Press, via EurekAlert!, a service of AAAS.
Fungi Respond To Climate Change
ScienceDaily (Apr. 25, 2007) — Climate change is dramatically altering the growing patterns of mushrooms, toadstools and other fungi, new research has found.
There are around 18,000 different species of fungi in the UK -- three times as many as all plants put together. They provide vital ecosystem services for the welfare of native trees and other plants, and are the natural recyclers of the planet, but until now their response to global climate change has not been examined.
A team from Cardiff University’s School of Biosciences working on a project led by Royal Holloway, University of London and with the Natural Environment Research Council Centre for Ecology and Hydrology studied more than 52,000 fungal fruiting records from nearly 1,400 localities collected in southern England between 1950 - 2005.
The study found that fungi are fruiting significantly earlier and for a longer period than ever before. In the 1950s fungi fruited over a period of around 33 days but this has more than doubled to nearly 75 days in the current decade.
Professor Lynne Boddy, Cardiff School of Biosciences said: "The increase in the overall fruiting period is dramatic, and much higher than equivalent spring data reported for plants, insects or birds."
The study found that the alteration in fungal fruiting mirrors changes in British temperatures that have occurred since 1975. The increase in late summer temperatures and autumnal rains has caused early season species to fruit earlier and late season species to continue to fruit later. Furthermore, climate warming seems to have caused significant numbers of species to begin fruiting in spring as well as autumn, suggesting increases in decay rates in forests.
--------------------------------------------------------------------------------
Adapted from materials provided by Cardiff University.
ScienceDaily (Apr. 25, 2007) — Climate change is dramatically altering the growing patterns of mushrooms, toadstools and other fungi, new research has found.
There are around 18,000 different species of fungi in the UK -- three times as many as all plants put together. They provide vital ecosystem services for the welfare of native trees and other plants, and are the natural recyclers of the planet, but until now their response to global climate change has not been examined.
A team from Cardiff University’s School of Biosciences working on a project led by Royal Holloway, University of London and with the Natural Environment Research Council Centre for Ecology and Hydrology studied more than 52,000 fungal fruiting records from nearly 1,400 localities collected in southern England between 1950 - 2005.
The study found that fungi are fruiting significantly earlier and for a longer period than ever before. In the 1950s fungi fruited over a period of around 33 days but this has more than doubled to nearly 75 days in the current decade.
Professor Lynne Boddy, Cardiff School of Biosciences said: "The increase in the overall fruiting period is dramatic, and much higher than equivalent spring data reported for plants, insects or birds."
The study found that the alteration in fungal fruiting mirrors changes in British temperatures that have occurred since 1975. The increase in late summer temperatures and autumnal rains has caused early season species to fruit earlier and late season species to continue to fruit later. Furthermore, climate warming seems to have caused significant numbers of species to begin fruiting in spring as well as autumn, suggesting increases in decay rates in forests.
--------------------------------------------------------------------------------
Adapted from materials provided by Cardiff University.
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