Featured Research

from universities, journals, and other organizations

It pays to cooperate: Yeast cells that share food have survival edge over freeloading neighbors

Date:
November 13, 2012
Source:
Massachusetts Institute of Technology
Summary:
Yeast cells that share food have a survival edge over their freeloading neighbors -- particularly when there is bacterial competition.

Sacharomyces cerevisiae cells in DIC microscopy.
Credit: Image courtesy of Massachusetts Institute of Technology

Many species exhibit cooperative survival strategies -- for example, sharing food or alerting other individuals when a predator is nearby. However, there are almost always freeloaders in the population who will take advantage of cooperators. This can be seen even among microbes such as yeast, where "cheaters" consume food produced by their neighbors without contributing any of their own.

In light of this, evolutionary biologists have long wondered why cooperation remains a viable survival strategy, since there will always be others who cheat. Now, MIT physicists have found a possible answer to this question: Among yeast, cooperative members of the population actually have a better chance of survival than cheaters when a competing species is introduced into an environment.

This experimental setup, in which yeast must coexist with a bacterial competitor, more closely mimics natural environments, where species often have to compete with one another for scarce food and other resources.

"It's very difficult to study these things in the truly natural context," says Jeff Gore, an assistant professor of physics at MIT and senior author of the new study, which appears in the journal Molecular Systems Biology on Nov. 13. "These experiments can act as a bridge between single-species experiments and very complicated ecosystem dynamics that are out there."

Hasan Celiker, an MIT graduate student in electrical engineering and computer science, is the paper's lead author.

Cheaters do prosper, sometimes

Gore and Celiker studied a strain of yeast that relies on small sugars such as glucose and fructose for nourishment. When yeast cells are grown in a test tube containing sucrose, some secrete an enzyme that breaks the sucrose down into smaller sugars, most of which diffuse away and are available to any nearby yeast cell.

In 2009, Gore and colleagues published a study showing that in a stable population of these yeast, freeloaders dominate. Only 14 percent of the yeast cells cooperate by secreting metabolic enzymes, while the rest enjoy the bounty of others' work.

In the new study, the researchers wanted to bring their experimental system closer to the complexity of natural environments. "Our approach is to start with the most simple system you can," Gore says. "Then we'd like to try to understand these more complicated interactions between different species, so as a baby step in that direction, we added a bacterial competitor."

This bacterial competitor consumes much of the sugar produced by the cooperative yeast, and also competes for other resources, such as nutrients. After these bacteria were added, the percentage of cooperators in the yeast population increased to about 45 percent.

This isn't because the yeast "decide" to become more cooperative, as humans might when faced with an external threat, Gore says. It's determined purely by genetics. "That's the point of doing experiments with microbial populations: There should be a mechanism that we can understand," he says.

Extra competition

In this case, the researchers found two mechanisms at work. First, in the face of extra competition for sugars, the cooperators have a slight advantage over cheaters because they have slightly easier access to the sugar they produce themselves.

A related mechanism involves population density. When bacteria are present, the overall yeast population stays smaller and is forced to spread out more, making it harder for the freeloaders to find food.

"The cheater cells can really spread when there are a lot of other yeast, because there's a lot of sugar out there for them. If there aren't very many yeast, then it's challenging for cheaters to spread," Gore says.

Though the experiment does not precisely replicate natural conditions, it does show that it is important to try to get as close to those conditions as possible, Gore says.

"If you just study something in isolation, such as yeast in a test tube, you might conclude that cooperation is very unstable," he says. "But if you look at these populations in the wild, where their densities are limited and they have to interact with all these other species, you might come to very different conclusions for how difficult it is for the cooperative behavior to survive."

In future studies, Gore hopes to add further complexity to the experimental microbial ecosystems, including varying the size of the yeast habitat.


Story Source:

The above story is based on materials provided by Massachusetts Institute of Technology. The original article was written by Anne Trafton. Note: Materials may be edited for content and length.


Journal Reference:

  1. Hasan Celiker, Jeff Gore. Competition between species can stabilize public-goods cooperation within a species. Molecular Systems Biology, 2012; 8 DOI: 10.1038/msb.2012.54

Cite This Page:

Massachusetts Institute of Technology. "It pays to cooperate: Yeast cells that share food have survival edge over freeloading neighbors." ScienceDaily. ScienceDaily, 13 November 2012. <www.sciencedaily.com/releases/2012/11/121113134803.htm>.
Massachusetts Institute of Technology. (2012, November 13). It pays to cooperate: Yeast cells that share food have survival edge over freeloading neighbors. ScienceDaily. Retrieved April 17, 2014 from www.sciencedaily.com/releases/2012/11/121113134803.htm
Massachusetts Institute of Technology. "It pays to cooperate: Yeast cells that share food have survival edge over freeloading neighbors." ScienceDaily. www.sciencedaily.com/releases/2012/11/121113134803.htm (accessed April 17, 2014).

Share This



More Plants & Animals News

Thursday, April 17, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Change of Diet Helps Crocodile Business

Change of Diet Helps Crocodile Business

Reuters - Business Video Online (Apr. 16, 2014) Crocodile farming has been a challenge in Zimbabwe in recent years do the economic collapse and the financial crisis. But as Ciara Sutton reports one of Europe's biggest suppliers of skins to the luxury market has come up with an unusual survival strategy - vegetarian food. Video provided by Reuters
Powered by NewsLook.com
Could Even Casual Marijuana Use Alter Your Brain?

Could Even Casual Marijuana Use Alter Your Brain?

Newsy (Apr. 16, 2014) A new study conducted by researchers at Northwestern and Harvard suggests even casual marijuana use can alter your brain. Video provided by Newsy
Powered by NewsLook.com
Thousands Of Vials Of SARS Virus Go Missing

Thousands Of Vials Of SARS Virus Go Missing

Newsy (Apr. 16, 2014) A research institute in Paris somehow misplaced more than 2,000 vials of the deadly SARS virus. Video provided by Newsy
Powered by NewsLook.com
Raw: Three Rare White Tiger Cubs Debut at Zoo

Raw: Three Rare White Tiger Cubs Debut at Zoo

AP (Apr. 16, 2014) The Buenos Aires Zoo debuted a trio of rare white Bengal tiger cubs on Wednesday. (April 16) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins