Featured Research

from universities, journals, and other organizations

Lack of energy an enemy to antibiotic-resistant microbes

Date:
February 11, 2013
Source:
Rice University
Summary:
Researchers "cured" a strain of bacteria of its ability to resist an antibiotic in an experiment that has implications for a long-standing public health crisis.

As a bacteria cell’s metabolic burden rises due to lack of nutrients or oxygen, its ability to transfer antibiotic-resistant genes to new generations declines. Rice University researchers were able to eliminate tetracycline resistance genes from a strain of bacteria found in the environment.
Credit: Alvarez Group/Rice University

Rice University researchers "cured" a strain of bacteria of its ability to resist an antibiotic in an experiment that has implications for a long-standing public health crisis.

Rice environmental engineer Pedro Alvarez and his team managed to remove the ability of the Pseudomonas aeruginosa microorganism to resist the antibiotic medication tetracycline by limiting its access to food and oxygen.

Over 120 generations, the starving bacteria chose to conserve valuable energy rather than use it to pass on the plasmid -- a small and often transmissible DNA element -- that allows it to resist tetracycline.

The researchers' results, reported this month in the American Chemical Society journal Environmental Science and Technology, are the latest in a long effort to understand the environmental aspects of antibiotic resistance, which threatens decades of progress in fighting disease.

"The propagation of antibiotic resistance has been perceived as a medical or microbiology-related problem," Alvarez said. "And it truly is a serious problem. But what many people miss is that it is also an environmental pollution problem. A lot of the antibiotic-resistant bacteria originate in animal agriculture, where there is overuse, misuse and abuse of antibiotics."

Alvarez contended that confined animal feeding operations (CAFOs) are potential sources of environmental contamination by antibiotics and the associated antibiotic-resistant genes that find their way into the ground, water and ultimately the food supply.

"We started with the hypothesis that microbes don't like to carry excess baggage," he said. "That means they will drop genes they're not using because there is a metabolic burden, a high energy cost, to keeping them."

The Rice researchers tested their theory on two strains of bacteria, P. aeruginosa, which is found in soil, and E. coli, which carries resistant genes directly from animals through their feces into the environment.

By slowly starving them of nutrients and/or oxygen through successive generations, they found that in the absence of tetracycline, both microbes dumped the resistance plasmid, though not entirely in the case of E. coli. But P. aeruginosa completely shed the genetic element responsible for resistance, which made it susceptible once again to antibiotics. When a high level of tetracycline was present, both microbes retained a level of resistance.

One long-recognized problem with antibiotics is that they tend to snatch defeat from the jaws of victory. If any antibiotic-resistant bacteria are part of a biological mix, whether in a person, an animal or in the environment, the weak microbes will die and the resistant will survive and propagate; this process is known by biologists as "selective pressure."

So there is incentive to eliminate the resistance plasmid from bacteria in the environment as close to the source as possible. The experiments point to possible remediation strategies, Alvarez said. "There are practical implications to what we did," he said. "If we can put an anaerobic barrier at the point where a lagoon drains into the environment, we will essentially exert selective pressure for the loss of antibiotic-resistant genes and mitigate the propagation of these factors."

An anaerobic barrier may be as cheap and simple as mulch in the drainage channel, he said. "If you have a CAFO draining through a channel, then put an anaerobic barrier in that channel. A mulch barrier will do." He said a mulch barrier only a meter thick could contact slow-moving groundwater for more than a month. "That may not kill the bacteria, but it's enough to have bacteria notice a deficiency in their ability to obtain energy from the environment and feel the stress to dump resistant genes."

Alvarez has been chipping away at the problem since moving to Rice from the University of Iowa in 2004, even without American funding for research. His study of the Haihe River in China, funded by the Chinese government and published last year, found tetracycline resistance genes are common in the environment there as well. "We tested water and river sediment and couldn't find a sample that didn't have them," he said.

"Our philosophy in environmental engineering is that an ounce of prevention is worth more than a pound of remediation," Alvarez said. "Prevention here is, basically, don't let these genes proliferate. Don't let them amplify in the environment. Stop them before they're released. And one easy way is to put up an anaerobic barrier."

Co-authors of the paper are Rice alumni Michal Rysz, now an environmental engineer at GSI Environmental Inc., Houston; William Mansfield, a scientist at the EPA in Dallas; and John Fortner, an assistant professor at Washington University, St. Louis. Alvarez is the George R. Brown Professor and chair of the Department of Civil and Environmental Engineering at Rice.


Story Source:

The above story is based on materials provided by Rice University. The original article was written by Mike Williams. Note: Materials may be edited for content and length.


Journal Reference:

  1. Michal Rysz, William R. Mansfield, John D. Fortner, Pedro J. J. Alvarez. Tetracycline Resistance Gene Maintenance under Varying Bacterial Growth Rate, Substrate and Oxygen Availability, and Tetracycline Concentration. Environmental Science & Technology, 2013; 130205085536002 DOI: 10.1021/es3035329

Cite This Page:

Rice University. "Lack of energy an enemy to antibiotic-resistant microbes." ScienceDaily. ScienceDaily, 11 February 2013. <www.sciencedaily.com/releases/2013/02/130211150747.htm>.
Rice University. (2013, February 11). Lack of energy an enemy to antibiotic-resistant microbes. ScienceDaily. Retrieved August 23, 2014 from www.sciencedaily.com/releases/2013/02/130211150747.htm
Rice University. "Lack of energy an enemy to antibiotic-resistant microbes." ScienceDaily. www.sciencedaily.com/releases/2013/02/130211150747.htm (accessed August 23, 2014).

Share This




More Plants & Animals News

Saturday, August 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Endangered Red Wolves Face Uncertain Future

Endangered Red Wolves Face Uncertain Future

AP (Aug. 22, 2014) A federal judge temporarily banned coyote hunting to save endangered red wolves, but local hunters say that the wolf preservation program does more harm than good. Meanwhile federal officials are reviewing its wolf program in North Carolina. (Aug. 22) Video provided by AP
Powered by NewsLook.com
Farm Resurgence Grows With Younger Crowd

Farm Resurgence Grows With Younger Crowd

AP (Aug. 22, 2014) New England farms are seeing a surge in younger farm hands as the 'buy local' food movement grows across the country. (Aug. 22) Video provided by AP
Powered by NewsLook.com
Drug Used To Treat 'Ebola's Cousin' Shows Promise

Drug Used To Treat 'Ebola's Cousin' Shows Promise

Newsy (Aug. 21, 2014) An experimental drug used to treat Marburg virus in rhesus monkeys could give new insight into a similar treatment for Ebola. Video provided by Newsy
Powered by NewsLook.com
Terrifying City-Dwelling Spiders Are Bigger And More Fertile

Terrifying City-Dwelling Spiders Are Bigger And More Fertile

Newsy (Aug. 21, 2014) According to a new study, spiders that live in cities are bigger, fatter and multiply faster. Video provided by Newsy
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