Featured Research

from universities, journals, and other organizations

Life scientists, colleagues differentiate microbial good and evil

Date:
January 9, 2014
Source:
University of California - Los Angeles
Summary:
To safely use bacteria in biotechnology and agriculture, where bacteria can help to fertilize plants, understanding the differences between harmful and healthy bacterial strains is vital. One member of a family of bacteria called Burkholderiaceae is known as a potential bioterrorist agent and not used in agriculture. Can the microbial good and evil be told apart? Yes, biologists report.

Burkholderia silvatlantica on root of a honey locust plant.
Credit: Michelle R. Lum

To safely use bacteria in agriculture to help fertilize crops, it is vital to understand the difference between harmful and healthy strains. The bacterial genus Burkholderia, for example, includes dangerous disease-causing pathogens -- one species has even been listed as a potential bioterrorist agent -- but also many species that are safe and important for plant development.

Can the microbial good and evil be told apart? Yes, UCLA life scientists and an international team of researchers report Jan. 8 in the online journal PLOS ONE.

"We have shown that a certain group of Burkholderia, which have just been discovered in the last 12 years as plant-growth promoting bacteria, are not pathogenic," said the study's senior author, Ann Hirsch, a professor of molecular, cell, and developmental biology in the UCLA College of Letters and Science. "This opens up the possibility of using these particular species for promoting plant growth through the process of nitrogen fixation, particularly in areas of climate change. This will have a major impact, especially on people in the developing world in producing protein-rich crops."

Nitrogen fixation is a process by which helpful bacteria that have entered the roots of plants convert nitrogen in the atmosphere into ammonia, which helps the plants thrive. The findings of Hirsch and her colleagues indicate that several recently discovered Burkholderia species, including Burkholderia tuberum, could be used -- cautiously -- in nitrogen fixing. These species, the scientists discovered, lack those genes that make other Burkholderia species harmful agents of infection.

"Bacteria that fix atmospheric nitrogen into ammonia, such as Burkholderia,are critical for plant growth," said Hirsch, whose laboratory studies many aspects of the complex symbiosis between plants and bacteria. "We're especially interested in these recently described Burkholderia species because they are found primarily in the dry and acidic soils of the Southern Hemisphere, making them potentially important for agriculture in less productive areas."

For their study, the UCLA life scientists performed a bioinformatics analysis of four symbiotic Burkholderia species, all of which fix nitrogen and one, B. tuberum, which "nodulates legumes." They found a strong distinction between genes in these beneficial strains and in pathogenic strains. They searched for genes typically involved in infection -- for attaching to and invading cells or for secreting toxins. Unlike their dangerous cousins, the four symbiotic Burkholderia species did not have genes associated with the virulence systems found in the pathogenic species.

Burkholderia were first discovered as plant pathogens in 1949 by Walter Burkholder, who identified them as the agent causing onion-skin rot. Later, Burkholderia species were identified as the causative agent of the disease melioidosis, a public health threat, especially in tropical countries like Thailand and in parts of Australia. B. pseudomallei, which causes melioidosis, is classified by the Centers for Disease Control and Prevention as a potential bioterrorist agent.

Other Burkholderia belong to the Burkholderia cepacia complex, a group of related bacteria that are not true pathogens but can cause "opportunistic" or hospital-acquired infections in people with weakened immune systems or with cystic fibrosis. Although some members of the Burkholderia cepacia complex have been used to protect plants from dangerous fungal infections, their potential to cause infection has resulted in severe limits on their use in agriculture.

It wasn't until many decades after Burkholder's discovery that closely related Burkholderia species were found to enter plant roots not as pathogens but as helpful symbionts -- generating root nodules in which the bacteria provide nitrogen fertilizer to the plant. Bacteria that cause the formation of these nodules in legumes, such as soybeans, alfalfa and peanuts, are crucial to sustainable agricultural systems, Hirsch said.

Although the nodulating, symbiotic species of Burkholderia are related to the more dangerous species, a detailed analysis of their evolutionary relationships published earlier this year by Hirsch and her colleagues showed that the two groups have a distinct evolutionary lineage.

The harmful Burkholderia species are more resistant to antibiotics than the symbiotic and agricultural strains. In addition to the bioinformatics analysis in the current study, the team analyzed resistance to a panel of common antibiotics, and tested the potential of different Burkholderia species to cause infection in laboratory conditions.

Experiments testing the potential of the four symbiotic species to cause infection in the small nematode worm known as Caenorhabditis elegans and in human cells grown in culture verified the bioinformatics analysis, showing that the bacteria were not harmful.

"We used a variety of detailed experiments to make sure that the symbiotic species are safe to put into farmers' fields and home gardens, just like currently used nitrogen-fixing bacteria," Hirsch said. "Our goal is to have these newly discovered nitrogen-fixing bacteria be used for a more sustainable approach to agriculture in the future."

Co-authors of the PLOS ONE research included Annette Angus and Christina Agapakis, UCLA postdoctoral scholars in Hirsch's laboratory; Stephanie Fong, Paul Yang, Nannie Song and Stephanie Kano, former UCLA undergraduate researchers in Hirsch's laboratory; Shailaja Yerrapragada of the Baylor College of Medicine in Houston; Paulina Estrada-de los Santos of the department of microbiology at Mexico's Instituto Politécnico Nacional, Prolongación de Carpio y Plan de Ayala; Jésus Caballero-Mellado (now deceased) of the Genomic Sciences Center at the National Autonomous University of Mexico; Sergio de Faria of Brazil's Embrapa Agrobiologia; Felix Dakora of the chemistry department of Tshwane University of Technology in South Africa; and George


Story Source:

The above story is based on materials provided by University of California - Los Angeles. Note: Materials may be edited for content and length.


Journal Reference:

  1. Annette A. Angus, Christina M. Agapakis, Stephanie Fong, Shailaja Yerrapragada, Paulina Estrada-de los Santos, Paul Yang, Nannie Song, Stephanie Kano, Jésus Caballero-Mellado, Sergio M. de Faria, Felix D. Dakora, George Weinstock, Ann M. Hirsch. Plant-Associated Symbiotic Burkholderia Species Lack Hallmark Strategies Required in Mammalian Pathogenesis. PLoS ONE, 2014; 9 (1): e83779 DOI: 10.1371/journal.pone.0083779

Cite This Page:

University of California - Los Angeles. "Life scientists, colleagues differentiate microbial good and evil." ScienceDaily. ScienceDaily, 9 January 2014. <www.sciencedaily.com/releases/2014/01/140109092014.htm>.
University of California - Los Angeles. (2014, January 9). Life scientists, colleagues differentiate microbial good and evil. ScienceDaily. Retrieved July 28, 2014 from www.sciencedaily.com/releases/2014/01/140109092014.htm
University of California - Los Angeles. "Life scientists, colleagues differentiate microbial good and evil." ScienceDaily. www.sciencedaily.com/releases/2014/01/140109092014.htm (accessed July 28, 2014).

Share This




More Plants & Animals News

Monday, July 28, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Traditional African Dishes Teach Healthy Eating

Traditional African Dishes Teach Healthy Eating

AP (July 28, 2014) — Classes are being offered nationwide to encourage African Americans to learn about cooking fresh foods based on traditional African cuisine. The program is trying to combat obesity, heart disease and other ailments often linked to diet. (July 28) Video provided by AP
Powered by NewsLook.com
Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Asteroid's Timing Was 'Colossal Bad Luck' For The Dinosaurs

Newsy (July 28, 2014) — The asteroid that killed the dinosaurs struck at the worst time for them. A new study says that if it hit earlier or later, they might've survived. Video provided by Newsy
Powered by NewsLook.com
Raw: Sea Turtle Hatchlings Emerge from Nest

Raw: Sea Turtle Hatchlings Emerge from Nest

AP (July 27, 2014) — A live-streaming webcam catches loggerhead sea turtle hatchlings emerging from a nest in the Florida Keys. (July 27) Video provided by AP
Powered by NewsLook.com
Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Russia Saves Gecko Sex Satellite, Media Has Some Fun With It

Newsy (July 27, 2014) — The satellite is back under ground control after a tense few days, but with a gecko sex experiment on board, the media just couldn't help themselves. 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