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Microscopic Aquatic Predators Strongly Affect Infection Dynamics of a Globally Emerged Pathogen

Microscopic Aquatic Predators Strongly Affect Infection Dynamics of a Globally Emerged Pathogen | Biotic interactions | Scoop.it

Research on emerging infectious wildlife diseases has placed particular emphasis on host-derived barriers to infection and disease. This focus neglects important extrinsic determinants of the host/pathogen dynamic, where all barriers to infection should be considered when ascertaining the determinants of infectivity and pathogenicity of wildlife pathogens [1, 2 and 3]. Those pathogens with free-living stages, such as fungi causing catastrophic wildlife declines on a global scale [4], must confront lengthy exposure to environmental barriers before contact with an uninfected host [5, 6, 7 and 8]. Hostile environmental conditions therefore have the ability to decrease the density of infectious particles, reducing the force of infection and ameliorating the impact as well as the probability of establishing an infection [9]. Here we show that, in nature, the risk of infection and infectious burden of amphibians infected by the chytrid fungus Batrachochytrium dendrobatidis (Bd) have a significant, site-specific component, and that these correlate with the microfauna present at a site. Experimental infections show that aquatic microfauna can rapidly lower the abundance and density of infectious stages by consuming Bd zoospores, resulting in a significantly reduced probability of infection in anuran tadpoles. Our findings offer new perspectives for explaining the divergent impacts of Bd infection in amphibian assemblages and contribute to our understanding of ecosystem resilience to colonization by novel pathogens.

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Water Stress Strengthens Mutualism Among Ants, Trees, and Scale Insects

Water Stress Strengthens Mutualism Among Ants, Trees, and Scale Insects | Biotic interactions | Scoop.it

The strength of ecological interactions, measured as the costs or benefits sustained by each species, depends on the environmental context in which the interaction occurs. Stressful environmental conditions should favor trading between species that can produce a given resource or service at the lowest cost. Mutualisms, in which both interacting species incur a net benefit, may thus strengthen under stressful conditions. Here we examine an ant–plant mutualism, in which plants provide food and housing for ants and ants defend plants against leaf-eating insects, along a four-fold annual precipitation gradient comprising tropical sites in Mexico and Central America. We show that the strength of the mutualism, in terms of carbon investment by plants and leaf defense by ants, increases as water availability decreases. Carbon shortages are more frequent where water is scarce and increase the risk that plants will die if all of their leaves are eaten by herbivores. Trees appear to invest more in ant defenders when water is scarce to insure themselves against extreme herbivory. Water availability thus indirectly determines the outcomes of this ant–plant mutualism, which suggests that the increasing frequency of extreme climate events in the tropics will have important ecological consequences.

 

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Host and parasite diversity jointly control disease risk in complex communities

Host and parasite diversity jointly control disease risk in complex communities | Biotic interactions | Scoop.it

Ongoing losses of biodiversity underscore the need to understand how species loss affects infectious diseases. Recognizing that most communities include multiple hosts and pathogens, we tested how variation in host and parasite diversity influenced disease risk. By combining field surveys and experiments involving amphibian hosts and trematode parasites, we show that realistic changes in host and parasite richness inhibit transmission of the deadliest parasite, Ribeiroia ondatrae. Increased host richness consistently reduced infections by Ribeiroia and the total parasite community. Importantly, however, parasite richness further dampened pathogen transmission, and the most diverse assemblages reduced Ribeiroia transmission by >50%. These findings emphasize the “hidden” role of parasite communities in diversity–disease interactions and the value of a community-based approach to infectious disease.

Tom Nuhse's insight:

See also this nice review in Scitable:

Preston, D. & Johnson, P. (2012) Ecological Consequences of Parasitism. Nature Education Knowledge 3(10):47

http://www.nature.com/scitable/knowledge/library/ecological-consequences-of-parasitism-13255694

 

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Evolution of Camouflage Drives Rapid Ecological Change in an Insect Community

Evolution of Camouflage Drives Rapid Ecological Change in an Insect Community | Biotic interactions | Scoop.it
Tom Nuhse's insight:

Examples for ecological parameters driving evolution are plentiful, but until recently evolutionary changes have been thought too slow to influence community dynamics, population sizes etc. Farkas et al. manipulate the visibility of stick insects (Timema cristinae) to bird predators and show that maladaptation has -via the degree of predation- ripple effects on arthropod density and diversity as well as herbivory overall.

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Herbivore exploits orally secreted bacteria to suppress plant defenses

Herbivore exploits orally secreted bacteria to suppress plant defenses | Biotic interactions | Scoop.it

Larval drool has been dyed fluorescent green to show how colorado beetle larvae leave oral secretions at feeding sites

Tom Nuhse's insight:

Plants have two major defence pathways that can only be activated in an either-or fashion: a salicylate-based pathway to ward off biotrophic pathogens, and a jasmonate-based one to fight herbivores and necrotrophs. Chung et al show that Colorado beetle larvae distract plants by activating the "wrong" (salicylate-based) pathway via bacteria in their "drool". As a consequence, the "right" pathway (that would for example trigger production of proteins that give the larvae indigestion and suppress their growth) is actively blocked.

This is an interesting reversal of a trick some plant pathogenic bacteria use -activation of the jasmonate pathway to block the appropriate salicylate-defence.

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Fecal Shield | The Bug Geek

Fecal Shield | The Bug Geek | Biotic interactions | Scoop.it

Poop, not parasites

Tom Nuhse's insight:

A great piece of detective work on a creepy picture that's been circulating on the web- see eg http://t.co/aT7yeQk03Z

This bug is parasitised by one parasitoid wasp larva, not dozens. The rest of what looks like squirming larvae is actually poop.

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Crop Killing Pests on the March

Crop Killing Pests on the March | Biotic interactions | Scoop.it

  Climate change has provoked migration of crop killing pests, who are spreading towards the Earth's poles at an alarming annual rate of 3 kilometers According to a recent press release from the University of Exeter, global warming is stirring a change in the movement of crop killing pests, which are on the march towards the poles of the north and south.

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Caffeine in Floral Nectar Enhances Pollinator’s Memory of Reward

Caffeine in Floral Nectar Enhances  Pollinator’s Memory of Reward | Biotic interactions | Scoop.it
Tom Nuhse's insight:

It's impossible to resist the temptation to say "bees get a buzz from caffeine"....

Quote:

"low doses of caffeine are mildly rewarding and enhance cognitive performance and memory retention"

 

Original article here:

http://www.sciencemag.org/content/339/6124/1202.abstract?ijkey=fb0e5fde6632db2e013d5209881ad40392cf0fb3&keytype2=tf_ipsecsha

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Invasive Harlequin Ladybird Carries Biological Weapons Against Native Competitors

Invasive Harlequin Ladybird Carries Biological Weapons Against Native Competitors | Biotic interactions | Scoop.it
Tom Nuhse's insight:

The Asian Harlequin ladybird (Harmonia axyridis) has been introduced as a biocontrol agent against aphids into the US and Europe and is now considered one of the world’s most invasive insects. While it was first thought that high levels of the alkaloid harmonin protected the invader's eggs from predation by native coccinellids, we now know that fungal parasites (microsporidia) are the actual weapon.

 

http://www.sciencemag.org/content/340/6134/862.abstract?ijkey=71b6ce96339fed6d5b8c599ee1234e707f58f714&keytype2=tf_ipsecsha

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Exclusive: Fungal Wars of The World - The rejected Nature cover!

Exclusive: Fungal Wars of The World - The rejected Nature cover! | Biotic interactions | Scoop.it

In exclusive, here is the now famous cover that was "rejected" by Nature - as narrated in the Science article "Attack of the Clones":

 

"When Nature recently accepted a review co-authored by Sarah Gurr, the plant pathologist from the University of Oxford in the United Kingdom sent the journal a self-produced image to consider for its cover. It shows a fungus looking like one of those colossal, menacing tripods from H. G. Wells's War of the Worlds, stalking through a field, with bats, frogs, and toads fleeing before it in a crazed panic. “Fungal Wars of the World,” Gurr called it. The picture didn't make it, but many scientists agree with its message: Fungi have now become a greater global threat to crops, forests, and wild animals than ever before..."

 

The cover was designed by Prof. Sarah Gurr and PhD student Sarah McCraw, University of Oxford. Check Sarah Gurr's website at http://dps.plants.ox.ac.uk/plants/staff/sarahgurr.aspx


Via Kamoun Lab @ TSL, Mary Williams
Tom Nuhse's insight:

Emerging infectious diseases caused by fungi threaten bats, amphibia, potatoes, wheat, elms and ash trees. Chances are we haven't seen the half of it. See the original article here:

http://www.nature.com/nature/journal/v484/n7393/full/nature10947.html

 

... and a summary here:

http://www.sciencemag.org/content/337/6095/636.full

 

but let's not forget that some fungi are our friends:

http://www.sciencemag.org/content/337/6101/1452.1.full

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Dimethyl Disulfide Produced by the Naturally Associated Bacterium Bacillus sp B55 Promotes Nicotiana attenuata Growth by Enhancing Sulfur Nutrition

Dimethyl Disulfide Produced by the Naturally Associated Bacterium Bacillus sp B55 Promotes Nicotiana attenuata Growth by Enhancing Sulfur Nutrition | Biotic interactions | Scoop.it
Tom Nuhse's insight:

Coyote tobacco with defects in sulfur assimilation encourages growth of root-associated Bacillus- and receives a smelly sulfur metabolite in return.

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Modelling the Evolutionary Dynamics of Viruses within Their Hosts: A Case Study Using High-Throughput Sequencing

Modelling the Evolutionary Dynamics of Viruses within Their Hosts: A Case Study Using High-Throughput Sequencing | Biotic interactions | Scoop.it

Photo courtesy of Southern IPM Center

Tom Nuhse's insight:

Competition, selection, genetic drift and Lotka-Volterra, all in a model system of potato virus Y and its host.

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FAO - News Article: Sting operation - jellyfish "blooms" may endanger fish stocks

FAO - News Article: Sting operation - jellyfish "blooms" may endanger fish stocks | Biotic interactions | Scoop.it
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Symbiotic bacteria appear to mediate hyena social odors

Symbiotic bacteria appear to mediate hyena social odors | Biotic interactions | Scoop.it
Tom Nuhse's insight:

Interesting experimental support for the fermentation hypothesis of animal communication. Symbiotic bacteria on the body surface and particularly in scent glands produce by anaerobic fermentation a cocktail of volatiles that co-varies with species, sex and reproductive state of hyenas. Empirical evidence for the fermentation hypothesis has previously been difficult to obtain; here, modern sequencing technology (again) reveals the level of diversity in microbial communities associated with animals.

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Symbiosis catalyses niche expansion and diversification

Symbiosis catalyses niche expansion and diversification | Biotic interactions | Scoop.it

Image by Jeffrey Joy, see Research Highlight in Nature http://www.nature.com/nature/journal/v494/n7436/full/494151c.html

 

Interactions between species are important catalysts of the evolutionary processes that generate the remarkable diversity of life. Symbioses, conspicuous and inherently interesting forms of species interaction, are pervasive throughout the tree of life. However, nearly all studies of the impact of species interactions on diversification have concentrated on competition and predation leaving unclear the importance of symbiotic interaction. Here, I show that, as predicted by evolutionary theories of symbiosis and diversification, multiple origins of a key innovation, symbiosis between gall-inducing insects and fungi, catalysed both expansion in resource use (niche expansion) and diversification. Symbiotic lineages have undergone a more than sevenfold expansion in the range of host-plant taxa they use relative to lineages without such fungal symbionts, as defined by the genetic distance between host plants. Furthermore, symbiotic gall-inducing insects are more than 17 times as diverse as their non-symbiotic relatives. These results demonstrate that the evolution of symbiotic interaction leads to niche expansion, which in turn catalyses diversification.

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Sustainable agriculture: possible trajectories from mutualistic symbiosis and plant neodomestication

Sustainable agriculture: possible trajectories from mutualistic symbiosis and plant neodomestication | Biotic interactions | Scoop.it
•  A more sustainable agriculture is required to accompany the human population growth.•  Crops have probably lost their ability to control bad versus good mutualists.•  Opportunities to make use of efficient mutualists for a plant neodomestication exist.•  An ecologically intensive agriculture taking advantage of native mutualists is likely.
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Horizontally Transmitted Symbionts and Host Colonization of Ecological Niches

Horizontally Transmitted Symbionts and Host Colonization of Ecological Niches | Biotic interactions | Scoop.it
Tom Nuhse's insight:

Pea aphids are famously host to vertically transmitted primary endosymbionts of the genus Buchnera, and the association is so close that the latter can be used to genotype the race of pea aphid. However, there are also a whole range of secondary symbionts that can be more or less freely exchanged. By identifying symbionts from more than 1100 aphid samples from around the world, Henry et al. show that secondary symbionts are a highly mobile "accessory" gene pool that is closely corelated with the ecological niche (host plant) occupied by the aphid host. By carefully analysing the phylogenies of symbionts and hosts, they show that colonisation with new bacterial lineages can facilitate the exploration of new habitats and food plants by the aphids.

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Bacteria from lean cage-mates help mice stay slim

Bacteria from lean cage-mates help mice stay slim | Biotic interactions | Scoop.it

The team took gut bacteria from four sets of human twins in which one of each pair was lean and one was obese, and introduced the microbes into mice bred to be germ-free. Mice given bacteria from a lean twin stayed slim, whereas those given bacteria from an obese twin quickly gained weight, even though all the mice ate about the same amount of food.

Tom Nuhse's insight:

Just another astonishing example for the deep impact of our gut microflora on our physiology and health. To be sure, gut microbiota are not the new "heavy bone structure" or "slow metabolism"; obesity in these mice depended on both microflora and diet.

 

Original article in Science:

http://www.sciencemag.org/content/341/6150/1241214.full.pdf

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Microbiota-liberated host sugars facilitate post-antibiotic expansion of enteric pathogens

Microbiota-liberated host sugars facilitate post-antibiotic expansion of enteric pathogens | Biotic interactions | Scoop.it
Tom Nuhse's insight:

How a course of antibiotic treatment can pave the way for pathogenic Clostridium difficile and Salmonella typhimurium. In a diverse gut microflora, mono- and oligosaccharides released from the host's mucus-lined gut are very efficiently used and catabolised. Antibiotics can disrupt this nutrient network, and some pathogens are particularly good at exploiting the available sugars.

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BBC Radio 4 - The Life Scientific, John Pickett

BBC Radio 4 - The Life Scientific, John Pickett | Biotic interactions | Scoop.it
Jim Al-Khalili meets John Pickett, whose recent work on GM wheat caused a public debate.
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A Common Signaling Process that Promotes Mycorrhizal and Oomycete Colonization of Plants (2012)

A Common Signaling Process that Promotes Mycorrhizal and Oomycete Colonization of Plants (2012) | Biotic interactions | Scoop.it

The symbiotic association between plants and arbuscular mycorrhizal fungi is almost ubiquitous within the plant kingdom [1], and the early stages of the association are controlled by plant-derived strigolactone acting as a signal to the fungus in the rhizosphere [2–4] and lipochito-oligosaccharides acting as fungal signals to the plant [5]. Hyphopodia form at the root surface, allowing the initial invasion, and this is analogous to appressoria, infection structures of pathogenic fungi and oomycetes. Here, we characterize RAM2, a gene of Medicago truncatula required for colonization of the root by mycorrhizal fungi, which is necessary for appropriate hyphopodia and arbuscule formation. RAM2 encodes a glycerol-3-phosphate acyl transferase (GPAT) and is involved in the production of cutin monomers. Plants defective in RAM2 are unable to be colonized by arbuscular mycorrhizal fungi but also show defects in colonization by an oomycete pathogen, with the absence of appressoria formation. RAM2 defines a direct signaling function, because exogenous addition of the C16 aliphatic fatty acids associated with cutin are sufficient to promote hyphopodia/ appressoria formation. Thus, cutin monomers act as plant signals that promote colonization by arbuscular mycorrhizal fungi, and this signaling function has been recruited by pathogenic oomycetes to facilitate their own invasion.

 

http://kamounlab.dreamhosters.com/pdfs/CurrBiol_2012.pdf


Via Kamoun Lab @ TSL
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Persistent predator–prey dynamics revealed by mass extinction

Persistent predator–prey dynamics revealed by mass extinction | Biotic interactions | Scoop.it
Tom Nuhse's insight:

Lotka-Volterra dynamics not just for lynx and snowshoe hare.

 

original article

http://www.pnas.org/content/108/20/8335.abstract

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Gut Bacteria Allows Insect Pest to Foil Farmers

Gut Bacteria Allows Insect Pest to Foil Farmers | Biotic interactions | Scoop.it
Here is a lesson that we’re going to be taught again and again in the coming years: Most animals are not just animals. They’re also collections of microbes. If you really want to understand the ani...
Tom Nuhse's insight:

Gut bacteria are our friends, as we have come to realise. However, they are also our enemies' friends... Based mostly on metabolic "services" provided by bacterial symbionts, some Western Corn Rootworms have found ways of surviving the antiherbivory defences of soybean which is commonly planted in rotation with corn to disrupt the pest's life cycle.

Original research article:

http://www.pnas.org/content/early/2013/06/19/1301886110.abstract

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Mom Knows Best: The Universality of Maternal Microbial Transmission

Mom Knows Best: The Universality of Maternal Microbial Transmission | Biotic interactions | Scoop.it
PLOS Biology is an open-access, peer-reviewed journal that features works of exceptional significance in all areas of biological science, from molecules to ecosystems, including works at the interface with other disciplines.
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Vertebrates and invertebrates alike transmit "the right kind of " microbiome in ways that are often amount to "pseudo-vertical" transmission.

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Two strains of bacteria team up, thrive on limited resources

Two strains of bacteria team up, thrive on limited resources | Biotic interactions | Scoop.it
In a discovery that further demonstrates just how unexpected and unusual nature can be, scientists have found two strains of bacteria whose symbiotic relationship is unlike anything seen before.
Tom Nuhse's insight:

A rare example of a bacterial symbiosis in anoxic ocean sediments near Baja California. ALso interesting to consider: is it mutualism, syntrophy, commensalism? The jury is out.

Original article here:

http://www.nature.com/nature/journal/v500/n7461/full/nature12365.html#affil-auth

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