Featured Research

from universities, journals, and other organizations

Dangerous strains of E. coli may linger longer in water than benign counterparts, study finds

Date:
June 13, 2013
Source:
University at Buffalo
Summary:
A toxin dangerous to humans may help E. coli fend off aquatic predators, enabling strains of E. coli that produce the toxin to survive longer in lake water than benign counterparts, a new study finds. The research may help explain why water quality tests don't always accurately capture health risks for swimmers.

he protist Tetrahymena hunts E. coli in this photo illustration, which features a microscope image of Tetrahymena (left).
Credit: Image courtesy of University at Buffalo

A toxin dangerous to humans may help E. coli fend off aquatic predators, enabling strains of E. coli that produce the toxin to survive longer in lake water than benign counterparts, a new study finds.

Researchers from the University at Buffalo and Mercyhurst University reported these results online June 7 in the journal Applied and Environmental Microbiology.

"The take-home lesson is that E. coli that produce Shiga toxin persisted longer in recreational water than E. coli that don't produce this toxin," said UB Professor of Biological Sciences Gerald Koudelka, PhD, who led the study. "This is because the toxin appears to help E. coli resist predation by bacterial grazers."

The findings have implications for water quality testing. They suggest that measuring the overall population of E. coli in a river or lake -- as many current tests do -- may be a poor way to find out whether the water poses a danger to swimmers.

Past research has shown that overall E. coli concentrations don't always correlate with the levels of dangerous, Shiga toxin-producing E. coli present in the water, Koudelka said. His new study provides one possible explanation for why this might be.

E. coli, short for Escherichia coli, is a bacteria found in human and animal intestines. Most types of E. coli are harmless. But those that produce Shiga toxin can make people very sick, causing symptoms such as hemorrhagic diarrhea. Severe cases can lead to death.

In their new study, Koudelka and his colleagues obtained water samples from Presque Isle State Park and Mill Creek Stream, both in northern Pennsylvania. The water contained protists -- tiny, single-cellular creatures that feed on E. coli.

To test how Shiga toxin affects E. coli's survival, the scientists placed several different strains of E. coli into the water samples: three strains of Shiga toxin-encoding E. coli (STEC), and three strains of E. coli that did not produce the toxin.

The results: The toxin producers fared much better against the grazing protists than their toxin-free counterparts. Over 24 hours, STEC populations fell by an average of 1.4-fold, in contrast to 2.5-fold for the Shiga-free bacteria.

The STEC strain that produced the most Shiga toxin also lasted the longest, persisting in water for about 48 hours before declining in numbers.

Each E. coli strain was tested in its own experiment (as opposed to one big experiment that included all six). All of the STEC strains studied were ones that had previously caused illness in humans.

The findings add to evidence suggesting that current water quality tests may not capture the whole story when it comes to E. coli danger in recreational waters, Koudelka said.

"If you're only testing generally for fecal indicator bacteria, you could miss the danger because it's possible to have low levels of E. coli overall, but have most of that E. coli be of the STEC variety," he said. "This would be worse than having a large E. coli population but no STEC."

The opposite problem can also occur, Koudelka said.

"You could have high E. coli populations in a lake, but absolutely no STEC," he said. "This is the economic part of it: It's a problem because you might have a beach that's closed for days even though it's safe."

The study was funded by the National Science Foundation and Mercyhurst University, and the research is part of Koudelka's ongoing investigations into the lives of aquatic microbes, including bacteria and protists. He is particularly interested in how one species may help regulate the level of others through predation and other interactions. Koudelka's work has shown that Shiga and other dangerous toxins probably arose as antipredator defenses in what he calls a "microbiological arms race," and not to kill humans.


Story Source:

The above story is based on materials provided by University at Buffalo. The original article was written by Charlotte Hsu. Note: Materials may be edited for content and length.


Journal Reference:

  1. S. A. Mauro, H. Opalko, K. Lindsay, M. P. Colon, G. B. Koudelka. The microcosm mediates the persistence of Shiga toxin producing E. coli (STEC) in freshwater ecosystems. Applied and Environmental Microbiology, 2013; DOI: 10.1128/AEM.01281-13

Cite This Page:

University at Buffalo. "Dangerous strains of E. coli may linger longer in water than benign counterparts, study finds." ScienceDaily. ScienceDaily, 13 June 2013. <www.sciencedaily.com/releases/2013/06/130613133618.htm>.
University at Buffalo. (2013, June 13). Dangerous strains of E. coli may linger longer in water than benign counterparts, study finds. ScienceDaily. Retrieved September 30, 2014 from www.sciencedaily.com/releases/2013/06/130613133618.htm
University at Buffalo. "Dangerous strains of E. coli may linger longer in water than benign counterparts, study finds." ScienceDaily. www.sciencedaily.com/releases/2013/06/130613133618.htm (accessed September 30, 2014).

Share This



More Plants & Animals News

Tuesday, September 30, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Earth Has Lost Half Its Vertebrate Wildlife Since 1970: WWF

Earth Has Lost Half Its Vertebrate Wildlife Since 1970: WWF

Newsy (Sep. 30, 2014) A new study published by the World Wide Fund for Nature found that more than half of the world's wildlife population has declined since 1970. Video provided by Newsy
Powered by NewsLook.com
California University Designs Sustainable Winery

California University Designs Sustainable Winery

Reuters - US Online Video (Sep. 27, 2014) Amid California's worst drought in decades, scientists at UC Davis design a sustainable winery that includes a water recycling system. Vanessa Johnston reports. Video provided by Reuters
Powered by NewsLook.com
Argentina Worries Over Decline of Soybean Prices

Argentina Worries Over Decline of Soybean Prices

AFP (Sep. 27, 2014) The drop in price of soy on the international market is a cause for concern in Argentina, as soybean exports are a major source of income for Latin America's third largest economy. Duration: 01:10 Video provided by AFP
Powered by NewsLook.com
Mama Bear, Cubs Hang out in California Backyard

Mama Bear, Cubs Hang out in California Backyard

Reuters - US Online Video (Sep. 27, 2014) A mama bear and her two cubs climb trees, wrestle and take naps in the backyard of a Monrovia, California home. Vanessa Johnston reports. Video provided by Reuters
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:

Strange & Offbeat Stories


Plants & Animals

Earth & Climate

Fossils & Ruins

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