Featured Research

from universities, journals, and other organizations

Human and soil bacteria swap antibiotic-resistance genes

Date:
August 30, 2012
Source:
Washington University School of Medicine
Summary:
Soil bacteria and bacteria that cause human diseases have recently swapped at least seven antibiotic-resistance genes, researchers at Washington University School of Medicine in St. Louis report Aug. 31 in Science.

Escherichia coli bacteria of the strain O157:H7. Soil bacteria and bacteria that cause human diseases have recently swapped at least seven antibiotic-resistance genes.
Credit: Janice Haney Carr

Soil bacteria and bacteria that cause human diseases have recently swapped at least seven antibiotic-resistance genes, researchers at Washington University School of Medicine in St. Louis report Aug. 31 in Science.

Related Articles


According to the scientists, more studies are needed to determine how widespread this sharing is and to what extent it makes disease-causing pathogens harder to control.

"It is commonplace for antibiotics to make their way into the environment," says first author Kevin Forsberg, a graduate student. "Our results suggest that this may enhance drug resistance in soil bacteria in ways that could one day be shared with bacteria that cause human disease."

Among the questions still to be answered: Did the genes pass from soil bacteria to human pathogens or vice versa? And are the genes just the tip of a vast reservoir of shared resistance? Or did some combination of luck and a new technique for studying genes across entire bacterial communities lead the scientists to discover the shared resistance genes?

Humans only mix their genes when they produce offspring, but bacteria regularly exchange genes throughout their lifecycles. This ability is an important contributor to the rapid pace of bacterial evolution. When a bacterial strain develops a new way to beat antibiotics, it can share the strategy not only with its descendants but also with other bacteria.

Earlier studies by other scientists have identified numerous resistance genes in strains of soil bacteria. However, unlike the seven genes described in this report, the earlier genes were dissimilar to their analogs in disease-causing bacteria, implying that they had crossed between the bacterial communities a long time ago.

Most of the antibiotics used to fight illness today originated from the soil. Bacteria use the antibiotics, in part, as weapons to compete with each other for resources and survival. Scientists have long acknowledged that gives environmental bacteria an evolutionary incentive to find ways to beat antibiotics.

"We wanted to try to get a broader sense of how often and extensively antibiotic-resistance genes are shared between environmental bacteria and pathogens," says senior author Gautam Dantas, PhD, assistant professor of pathology and immunology.

The researchers isolated bacteria from soil samples taken at various U.S. locations. The bacteria's DNA was broken into small chunks and randomly inserted into a strain of Escherichia coli that is vulnerable to antibiotics. Scientists treated the altered E. coli with multiple antibiotics.

"We knew that any E. coli that continued to grow after these treatments had picked up a gene from the soil bacteria that was helping it fight the antibiotics," Forsberg says.

Scientists took the DNA from soil bacteria out of the surviving E. coli and prepared it for high-throughput sequencing. Dantas' laboratory has developed techniques that make it possible to simultaneously sequence and analyze thousands of chunks of DNA from many diverse microorganisms. The DNA can be selected for a single function, such as antibiotic resistance.

When the scientists compared antibiotic-resistance genes found in the soil bacteria to disease-causing bacteria, they were surprised to find some genes were identical not only in the sections of the genes that code for proteins but also in nearby non-coding sections that help regulate the genes' activities.

Since bacteria have such large population sizes and rapid reproduction times, their DNA normally accumulates mutations and other alterations much more quickly than the DNA of humans. The lack of changes in the resistance genes identified in the study suggests that the transfers of the genes must have occurred fairly recently, according to Dantas.

In some soil bacteria, the genes are present in clusters that make the bacteria resistant to multiple classes of antibiotics, including forms of penicillin, sulfonamide and tetracycline.

"I suspect the soil is not a teeming reservoir of resistance genes," Dantas says. "But if factory farms or medical clinics continue to release antibiotics into the environment, it may enrich that reservoir, potentially making resistance genes more accessible to infectious bacteria."


Story Source:

The above story is based on materials provided by Washington University School of Medicine. The original article was written by Michael C. Purdy. Note: Materials may be edited for content and length.


Journal Reference:

  1. K. J. Forsberg, A. Reyes, B. Wang, E. M. Selleck, M. O. A. Sommer, G. Dantas. The Shared Antibiotic Resistome of Soil Bacteria and Human Pathogens. Science, 2012; 337 (6098): 1107 DOI: 10.1126/science.1220761

Cite This Page:

Washington University School of Medicine. "Human and soil bacteria swap antibiotic-resistance genes." ScienceDaily. ScienceDaily, 30 August 2012. <www.sciencedaily.com/releases/2012/08/120830141343.htm>.
Washington University School of Medicine. (2012, August 30). Human and soil bacteria swap antibiotic-resistance genes. ScienceDaily. Retrieved December 20, 2014 from www.sciencedaily.com/releases/2012/08/120830141343.htm
Washington University School of Medicine. "Human and soil bacteria swap antibiotic-resistance genes." ScienceDaily. www.sciencedaily.com/releases/2012/08/120830141343.htm (accessed December 20, 2014).

Share This


More From ScienceDaily



More Plants & Animals News

Saturday, December 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Researchers Test Colombian Village With High Alzheimer's Rates

Researchers Test Colombian Village With High Alzheimer's Rates

AFP (Dec. 19, 2014) In Yarumal, a village in N. Colombia, Alzheimer's has ravaged a disproportionately large number of families. A genetic "curse" that may pave the way for research on how to treat the disease that claims a new victim every four seconds. Duration: 02:42 Video provided by AFP
Powered by NewsLook.com
Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Monarch Butterflies Descend Upon Mexican Forest During Annual Migration

Reuters - Light News Video Online (Dec. 19, 2014) Millions of monarch butterflies begin to descend onto Mexico as part of their annual migration south. Rough Cut (no reporter narration) Video provided by Reuters
Powered by NewsLook.com
The Best Protein-Filled Foods to Energize You for the New Year

The Best Protein-Filled Foods to Energize You for the New Year

Buzz60 (Dec. 19, 2014) The new year is coming and nothing will energize you more for 2015 than protein-filled foods. Fitness and nutrition expert John Basedow (@JohnBasedow) gives his favorite high protein foods that will help you build muscle, lose fat and have endless energy. Video provided by Buzz60
Powered by NewsLook.com
Birds Might Be Better Meteorologists Than Us

Birds Might Be Better Meteorologists Than Us

Newsy (Dec. 19, 2014) A new study suggests a certain type of bird was able to sense a tornado outbreak that moved through the U.S. a day before it hit. 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:

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