Featured Research

from universities, journals, and other organizations

Bacteria get new badge as planet's detoxifier

Date:
April 4, 2014
Source:
Desert Research Institute
Summary:
Amino acids, the fundamental building blocks of life, come in two forms that, like our left and right hand, have identical parts. But the two forms are not the same from a three dimensional perspective. One is the mirror image of the other. Proteins and enzymes in Earth organisms, without exception, all use L-forms. New evidence has demonstrated that Earth bacteria can do something that is quite unusual. Despite the fact that these bacteria are made of left-handed (L) amino acids, they are able to grow on right-handed (D) amino acids. The study takes a closer look at what these implications mean for studying organisms on Earth and beyond.

A study published this week in PLOS ONE authored by Dr. Henry Sun and his postdoctoral student Dr. Gaosen Zhang of Nevada based research institute DRI provides new evidence that Earth bacteria can do something that is quite unusual. Despite the fact that these bacteria are made of left-handed (L) amino acids, they are able to grow on right-handed (D) amino acids. This DRI study, funded by the NASA Astrobiology Institute and the NASA Exobiology Program, takes a closer look at what these implications mean for studying organisms on Earth and beyond.

Related Articles


"This finding is important because D-amino acids are slowly produced in soils through geochemical transformation of L amino acids. If they were allowed to accumulate, they would poison the environment for plants and animals. Our research shows that it is the bacteria that prevent D-amino acids from accumulating to toxic levels," explains Dr. Sun, who has studied microbial life in extreme environments in the Antarctic dry valleys, the Atacama Desert, and Death Valley.

Amino acids, the fundamental building blocks of life, come in two forms that, like our left and right hand, have identical parts. But the two forms are not the same from a three dimensional perspective. One is the mirror image of the other. Proteins and enzymes in Earth organisms, without exception, all use L-forms. As expected, soil bacteria are very efficient at consuming L-amino acids from the medium. The researchers then presented the same bacteria D-amino acids. To their surprise, these life-incompatible forms too were rapidly consumed.

"We are not saying that the D-amino acids are assimilated as is. If incorporated into proteins, this amount of D-amino acids would kill the organisms," says Dr. Sun. "Rather, we think that a conversion occurred in the bacteria that turned the D-amino acids back into L-forms. All bacteria carry a specialized enzyme known as racemase which converts amino acids from one form to another," adds Dr. Sun.

This then raises another question: If all organisms on Earth synthesize L-amino acids, where do D-amino acids come from? Amino acids have the property of being able to spontaneously flip from one form to another, a process called racemization. Racemization is very slow. Most organisms do not live long enough for this process to kill the proteins and, ultimately, the organisms themselves. In soils, however, amino acids can be sequestered for thousands or even millions of years, allowing racemization to accumulate. Eventually, the concentrated D-amino acids are released into the environments -- to the waiting bacteria, rather than poisoning plant and animal life.

Bacteriologists have known that bacteria contain racemases, but they have always assumed that the enzymes were invented for making D-amino acids. Unlike plants and animals, bacteria need a small amount of D-amino acids, not to incorporate into proteins, but to incorporate into cell walls to increase resistance and stability.

"But this cannot be the reason that bacteria invented the racemase. If D-amino acids are toxic, you have to invent a detoxification mechanism first before you go around and make more of the stuff. We think it is much more likely that the racemase originated initially as a detoxification enzyme. Only later, do bacteria, now immune to D-amino acid toxicity, start to make D-amino acids for constructive purposes. The D-amino acid-making function, therefore, is a secondary biological invention," says Dr. Sun.

"The implications of our study go beyond Earth. The steps that led to the invention of racemases on Earth would also exist on other planets, even if life uses D- instead of L-amino acids. This means that D-bacteria would also have to invent racemases and, as a result, would consume L-amino acids for nutrients. This creates a scenario that scientists charged with the duty of protecting Earth from foreign organisms haven't thought about," says Dr. Sun. "If D-bacteria ever visit us on Earth, they would compete with native bacteria for nutrients," he adds.


Story Source:

The above story is based on materials provided by Desert Research Institute. Note: Materials may be edited for content and length.


Journal Reference:

  1. Gaosen Zhang, Henry J. Sun. Racemization in Reverse: Evidence that D-Amino Acid Toxicity on Earth Is Controlled by Bacteria with Racemases. PLoS ONE, 2014; 9 (3): e92101 DOI: 10.1371/journal.pone.0092101

Cite This Page:

Desert Research Institute. "Bacteria get new badge as planet's detoxifier." ScienceDaily. ScienceDaily, 4 April 2014. <www.sciencedaily.com/releases/2014/04/140404085809.htm>.
Desert Research Institute. (2014, April 4). Bacteria get new badge as planet's detoxifier. ScienceDaily. Retrieved March 1, 2015 from www.sciencedaily.com/releases/2014/04/140404085809.htm
Desert Research Institute. "Bacteria get new badge as planet's detoxifier." ScienceDaily. www.sciencedaily.com/releases/2014/04/140404085809.htm (accessed March 1, 2015).

Share This


More From ScienceDaily



More Plants & Animals News

Sunday, March 1, 2015

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Whale-Watching Scientists Spot Baby Orca

Whale-Watching Scientists Spot Baby Orca

AP (Feb. 28, 2015) Researchers following endangered killer whales spotted a baby orca off the coast of Washington state, the third birth documented this winter but still leaving the population dangerously low. (Feb. 28) Video provided by AP
Powered by NewsLook.com
The Best Drinks for Your Health

The Best Drinks for Your Health

Buzz60 (Feb. 27, 2015) When it comes to health and fitness, there&apos;s lots of talk about what foods to eat, but there are a few liquids that can promote good nutrition. Krystin Goodwin (@krystingoodwin) has the healthiest drinks to boost your health! Video provided by Buzz60
Powered by NewsLook.com
Cherries, Snap Peas and More Tasty Spring Produce

Cherries, Snap Peas and More Tasty Spring Produce

Buzz60 (Feb. 27, 2015) From sweet cherries to sugar snap peas, spring is the peak season for some of the tastiest and healthiest produce. Krystin Goodwin (@Krystingoodwin) has the best seasonal fruits and veggies to spring in to good health! Video provided by Buzz60
Powered by NewsLook.com
The Best Foods to Battle Stress

The Best Foods to Battle Stress

Buzz60 (Feb. 26, 2015) If you&apos;re dealing with anxiety, there are a few foods that can help. Krystin Goodwin (@krystingoodwin) has the best foods to tame stress. Video provided by Buzz60
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