Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Microbes compete with animals for food by making it stink

03.11.2006
Microbes may compete with large animal scavengers by producing repugnant chemicals that deter higher species from consuming valuable food resources -- such as decaying meat, seeds and fruit, a new study suggests.

Ecologists have long recognized microbes as decomposers and pathogens in ecological communities. But their role as classic consumers who produce chemicals to compete with larger animals could be an important and common interaction within many ecosystems -- and one that scientists often overlook, according to the authors of a paper published this week in the journal Ecology.

"There is the notion that these spoiled resources are not that important," said Mark Hay, a Georgia Institute of Technology professor of biology, who led a team of graduate students conducting the research. "But when you total them up, they are appreciable, especially in marine ecosystems.

"Microbes that can hold onto these resources and use them for their own growth would be advantaged over microbes that could not prevent their resource from being consumed by animals," Hay added. "If microbes could produce chemicals that prevented crabs or fishes from using these resources, then those microbes should gain an advantage and become more abundant."

As part of an interdisciplinary graduate training program funded by the National Science Foundation, Hay, two of his faculty colleagues and four Ph.D. students tested this notion with a field and lab study they began at the Skidaway Institute of Oceanography near Savannah, Ga., in summer 2002. They were prompted by an assertion made in a paper published in 1977 by ecologist Dan Janzen, who suggested that microbes are rotting fruits, molding seeds and spoiling meat to make these resources repugnant to other animals, allowing microbes to consume them instead.

To test whether aged meat attracts fewer consumers than fresher meat, researchers baited crab traps with menhaden -- a fish typically used for bait -- that had been rotting in a pool of warm water – some of it for one day and the rest for two days. They also baited other traps with freshly thawed menhaden, which contained relatively few microbes. Then they set the traps in the marshes near Skidaway Island and caught hundreds of stone crabs, as well as other crab species, fishes and snails.

Many more animals were attracted to the freshly thawed bait than the rotten fish. "So we assumed that had to do with palatability," Hay said. "It could have been that the predators didn't smell the rotten fish, but that's not consistent with what we know about carrion on the roadway. It could have been that the predators smelled it, but didn't want it."

Counting the species found in the traps confirmed the level of attraction to the various forms of the bait, but it didn't necessarily test feeding, Hay noted. "It could be that the rotten food is just as good, but a lot of the good smells have leached out in the water, so maybe it's just food that's harder for predators to find," he explained.

Researchers assessed their questions about feeding by conducting laboratory experiments.

To eliminate food avoidance because of texture, they fed stone crabs, lesser blue crabs and striped hermit crabs noodle-like test foods made from pureed forms of either the freshly thawed menhaden or the rotten bait. Researchers found that, no matter the rotten bait's texture, stone crabs avoided eating the rotted, microbe-laden food, but readily consumed the freshly thawed menhaden containing few microbes.

"Even when the stone crabs were handed the rotten fish, they didn't want to eat it," Hay said.

Next, researchers tested whether microbes directly affected the palatability of microbe-laden, rotting food. They placed menhaden in two different pools for two days -- one group in seawater where microbes were allowed to grow naturally and the other in seawater with the antibiotic chloramphenicol added to suppress microbe growth. In the lab, stone crabs readily ate both freshly thawed menhaden and fish that had soaked in water with antibiotics, but refused to eat the rotten fish not protected from microbial attack.

To determine if reducing bacterial growth affected an animal's ability to find the bait, researchers also repeated the trapping experiment in the marsh, but used newly thawed fish, fish soaked in antibiotic treated water and fish aged without antibiotics. They found that both freshly thawed bait and aged, antibiotic-treated bait attracted animals more frequently than traps containing aged, microbe-laden menhaden.

Then researchers extracted various compounds from the microbe-laden bait to test whether chemicals produced by the microbes were indeed responsible for these feeding and attraction behaviors.

They found that chemical extracts composed of numerous compounds suppressed stone crab feeding when added to otherwise palatable fish flesh. But, of the several specific compounds they isolated and identified, none of the compounds by itself had this effect, Hay noted. So the researchers could not pinpoint a single compound causing the behaviors.

"But we can say the effect is chemical because we got rid of the nutrient and texture aspects of the bait and determined that it's something in this fraction of the bait's chemistry," Hay said. "It's either a complex mix of chemicals or perhaps something we destroyed during our lab test processes or maybe a chemical present in a very small amount that we failed to identify. There's uncertainty about this."

What's certain is that microbes are an omnipresent part of the ecosystem, Hay said. "They are not passively waiting on the bottom of the marsh floor for the rest of the community to deliver feces and other wastes that are not useful to anybody else," he added. "They are also trying to grab what they can at the start."

Hay hopes the research will make ecologists think more critically about the broad role of microbes in the ecosystem. Microbes are often omitted or relegated to a minor role in food web diagrams, but they should be depicted as direct competitors with larger animals, he said.

Jane Sanders | EurekAlert!
Further information:
http://www.gatech.edu

More articles from Ecology, The Environment and Conservation:

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

nachricht Value from wastewater
16.08.2017 | Hochschule Landshut

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Researchers devise microreactor to study formation of methane hydrate

23.08.2017 | Materials Sciences

ShAPEing the future of magnesium car parts

23.08.2017 | Automotive Engineering

New insights into the world of trypanosomes

23.08.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>