Division of labor in the test tube: Bacteria grow faster if they feed each other

Dec 02, 2013
Bacteria that divide their metabolic labor (left colony) grow faster than bacterial cells that produce all amino acids on their own (right colony). Credit: Samay Pande, Max Planck Institute for Chemical Ecology

The division of labor is more efficient than a struggle through life without help from others – this is also true for microorganisms. Researchers from Research Group Experimental Ecology and Evolution at the Max Planck Institute for Chemical Ecology and their colleagues at the Friedrich Schiller University in Jena, Germany came to this conclusion when they performed experiments with microbes. The scientists worked with bacteria that were deficient in the production of a certain amino acid and therefore depended on a partner to provide the missing nutrient. Bacterial strains that complemented each other's need by providing the required amino acid showed a fitness increase of about 20% relative to a non-deficient strain without partner. This result helps to explain why cooperation is such a widespread model of success in nature.

Ecology and evolution: close relatives

Each life form on our planet has to adapt to its environment as good as it can. Apart from getting used to climate conditions and food supply, each species must get along with other organisms in the habitat. In the course of evolution species adapt continuously to each other and to the environment by changing their genetic features. This is why cold resistant species live at the poles and heat resistant species in the deserts. Also nutritional needs and metabolic regulation underlie the principle of evolution. So let's take a look at the world of microbes in this context!

Microbial communities

"No matter where you look: Microbial communities can be found in almost every habitat you can think of," says Christian Kost, leader of the research group "Experimental Ecology and Evolution" at the Max Planck Institute for Chemical Ecology in Jena, Germany. Microbes often live in symbiosis with higher organisms, but they also cooperate with each other in order to optimally utilize the resources that are available to them. Interestingly, a look at the genome of cooperating shows that some of them are unable to perform all vital metabolic functions on their own. Instead, they rely on their cooperative partner. Their environment, that is to say other organisms, provides the nutrients they cannot produce themselves anymore. However, the result of the cooperation is a risky dependency: If one partner is lost, the other dies as well. Can such a dependency in fact be a trait that is selected for and which is maintained for a longer period in a bacterial population? Is this assumption compatible with Darwin's theory of the "survival of the fittest"? If so, cooperating partners should perform as good or even better than without partner in terms of fitness.

Synthetic Ecology: simulating ecological parameters in a test tube

To bring a naturally evolved symbiotic community from the real world into the lab to study such cooperation, is often very difficult. Therefore, scientists used a synthetic model: Escherichia coli bacteria were genetically modified in such a way that one bacterial strain was unable to produce a certain amino acid anymore, such as tryptophan, but produced all other in high concentrations. If this strain grows in a culture with another strain unable to produce arginine, another amino acid, both strains are able to feed each other. Amazingly, such co-culture experiments showed that the growth of these bacterial cells was increased by 20% in comparison to the unmodified wild-type strain that was able to produce all essential amino acid by itself. The inability of the deficient strain to produce an essential amino acid had a positive effect on its growth when a partner was present that compensated this loss. This can be explained by the considerably reduced energy costs both strains had to invest for producing the exchanged amino acids. Specializing on the production of certain, but not all necessary amino acids made the bacterial cells more efficient and thus resulted in faster growth. Interestingly, the two cooperating, amino acid exchanging strains even outcompeted a self-sustaining wild-type strain.

The research results from Christian Kost's lab illustrate why symbiotic relationships with bacteria are so prevalent. In the course of evolution, an association may get so close that the mutualistic partners merge into a new, multicellular organism.

Explore further: Top Japan lab dismisses ground-breaking stem cell study

More information: Pande, S., Merker, H., Bohl, K., Reichelt, M., Schuster, S., de Figueiredo, L., Kaleta, C., Kost, C. (2013). Fitness and stability of obligate cross-feeding interactions that emerge upon gene loss in bacteria. The ISME Journal. Advance online publication 28 November 2013; DOI: 10.1038/ismej.2013.211

add to favorites email to friend print save as pdf

Related Stories

Simplifying genetic codes to look back in time

Aug 24, 2012

(Phys.org)— Daisuke Kiga and co-workers at the Department of Computational Intelligence and Systems Science at Tokyo Institute of Technology, together with researchers across Japan, have shown that simpler versions of the ...

Recommended for you

Top Japan lab dismisses ground-breaking stem cell study

7 hours ago

Japan's top research institute on Friday hammered the final nail in the coffin of what was once billed as a ground-breaking stem cell study, dismissing it as flawed and saying the work could have been fabricated.

Research sheds light on what causes cells to divide

Dec 24, 2014

When a rapidly-growing cell divides into two smaller cells, what triggers the split? Is it the size the growing cell eventually reaches? Or is the real trigger the time period over which the cell keeps growing ...

Locking mechanism found for 'scissors' that cut DNA

Dec 24, 2014

Researchers at Johns Hopkins have discovered what keeps an enzyme from becoming overzealous in its clipping of DNA. Since controlled clipping is required for the production of specialized immune system proteins, ...

Scrapie could breach the species barrier

Dec 24, 2014

INRA scientists have shown for the first time that the pathogens responsible for scrapie in small ruminants (prions) have the potential to convert the human prion protein from a healthy state to a pathological ...

Extracting bioactive compounds from marine microalgae

Dec 24, 2014

Microalgae can produce high value health compounds like omega-3s , traditionally sourced from fish. With declining fish stocks, an alternative source is imperative. Published in the Pertanika Journal of Tr ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.