Featured Research

from universities, journals, and other organizations

Microbiology: Free-for-all On The Leaf Surface

October 5, 2009
ETH Zurich
Scientists have examined the genes and proteins of bacteria that live on leaves to clarify which unicellular organisms are found on leaf surfaces and what they are doing there.

Electron microscope image of a leaf surface. Up to ten million unicellular organisms live on every square centimeter.
Credit: Image courtesy of ETH Zurich

For the first time, ETH Zurich scientists have examined the genes and proteins of bacteria that live on leaves to clarify which unicellular organisms are found on leaf surfaces and what they are doing there.

Related Articles

Bacteria are everywhere: in the ground, on the seabed, in boiling hot sources, in the gut. They are even on the surface of plants, and lots of them at that: one to ten million of the unicellular microorganisms live on every square centimeter of stem and foliage. At one billion square kilometers, the entire plant surface is estimated to be four times bigger than that of the earth, thus making the so-called phyllosphere “the largest biological surface inhabited by microorganisms”, as Julia Vorholt, a professor at the Institute of Microbiology at ETH Zurich, puts it. The bacteria in this ecosystem are so numerous that they influence the vital global carbon cycle.

Suitable methods previously lacking

For the layman, it is all the more astonishing that biologists still know so little about this habitat and its inhabitants. However, the scientists have been plagued by one fundamental problem: for decades, the methods simply did not exist to offer a realistic glimpse into the variety of microbial ecosystems. However, in recent years procedures from modern molecular biology have made it possible to gain an increasingly better understanding of the bacteria and their function in complex microbe communities. For instance, Julia Vorholt’s team of researchers has now for the first time analyzed worldwide the metagenome and the metaproteome of a natural bacterial biocoenosis on a grand scale – i.e. the genes and proteins of the bacteria – and thus obtained initial insights into microbial activity on foliage. “Two kinds of bacteria dominate this ecosystem”, explains Vorholt: members of the methylobacterium genus and unicellular organisms from the sphingomonas genus.

The scientists began by collecting leaves from soy and clover plants and mouse-ear cress (Arabidopsis thaliana), then washed the bacteria off and skillfully processed the samples using specifically established methods. The proteins in the complex mixtures were cut into small pieces and analyzed with what Vorholt refers to as “hyper-sensitive mass spectrometers from the Functional Genomics Center Zurich”. The scientists then compared the structure of the fragments with known protein structures in international databases. “This enables us to identify the proteins and get an indication of which proteins the bacteria need under the given environmental conditions”, stresses the microbiologist from ETH Zurich.

Genes and proteins unmask identity

In order to obtain clues about proteins not yet recorded in the databases, the scientists also analyzed the genomes of the bacteria community. The genes indicate which proteins might be produced in a cell – “might” because cells only convert part of their genes into proteins. Together, all the genome and proteome data reveal the identity of the microorganisms, their potential capabilities and activity on the leaf surface.

Result: whatever the plant, bacteria from the sphingomonas and methylobacterium genera and their proteins always dominated the scenery. In all, the researchers found over 20 bacteria genera with about 100 different species. In doing so, the team from ETH Zurich also discovered previously unknown proteins, “which appear to be important for most bacteria on the leaves of all three plants studied”, says Julia Vorholt.

The Zurich team also came across an equally abundant protein among the methylobacteria that is similar to a known protein and important for the unicellular organisms’ metabolism. Methylobacteria convert the methanol produced by the plants into carbon dioxide for energy and nourishment. Bacteria from the sphingomonas genus, however, are less specialized and utilize different food and energy sources, such as sugar for instance. At least, this is what the many transporter proteins discovered by the ETH-Zurich biologists suggest.

Give and take?

The most interesting of the proteins now serve as a spring board for new experiments. The questions: what is the relationship between the bacteria and the plants? Do they solely use them as a source of nourishment and energy? Or do they give the plants something in return? This is easily conceivable; after all, plants are exposed to harmful attacks from microorganisms on a daily basis – transferred by insects or in the air. It is perfectly feasible that the colonization by microbes like methylobacteria or sphingomonas could protect the plants from such attacks. “Maybe the bacteria even produce antibiotics to keep the plants healthy”, speculates Julia Vorholt.

Story Source:

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

Journal Reference:

  1. Delmotte et al. Community proteogenomics reveals insights into the physiology of phyllosphere bacteria. Proceedings of the National Academy of Sciences, 2009; 106 (38): 16428 DOI: 10.1073/pnas.0905240106

Cite This Page:

ETH Zurich. "Microbiology: Free-for-all On The Leaf Surface." ScienceDaily. ScienceDaily, 5 October 2009. <www.sciencedaily.com/releases/2009/09/090927160422.htm>.
ETH Zurich. (2009, October 5). Microbiology: Free-for-all On The Leaf Surface. ScienceDaily. Retrieved December 19, 2014 from www.sciencedaily.com/releases/2009/09/090927160422.htm
ETH Zurich. "Microbiology: Free-for-all On The Leaf Surface." ScienceDaily. www.sciencedaily.com/releases/2009/09/090927160422.htm (accessed December 19, 2014).

Share This

More From ScienceDaily

More Plants & Animals News

Friday, December 19, 2014

Featured Research

from universities, journals, and other organizations

Featured Videos

from AP, Reuters, AFP, and other news services

Navy Unveils Robot Fish

Navy Unveils Robot Fish

Reuters - Light News Video Online (Dec. 18, 2014) The U.S. Navy unveils an underwater device that mimics the movement of a fish. Tara Cleary reports. Video provided by Reuters
Powered by NewsLook.com
Kids Die While Under Protective Services

Kids Die While Under Protective Services

AP (Dec. 18, 2014) As part of a six-month investigation of child maltreatment deaths, the AP found that hundreds of deaths from horrific abuse and neglect could have been prevented. AP's Haven Daley reports. (Dec. 18) Video provided by AP
Powered by NewsLook.com
When You Lose Weight, This Is Where The Fat Goes

When You Lose Weight, This Is Where The Fat Goes

Newsy (Dec. 17, 2014) Can fat disappear into thin air? New research finds that during weight loss, over 80 percent of a person's fat molecules escape through the lungs. Video provided by Newsy
Powered by NewsLook.com
The Hottest Food Trends for 2015

The Hottest Food Trends for 2015

Buzz60 (Dec. 17, 2014) Urbanspoon predicts whicg food trends will dominate the culinary scene in 2015. Mara Montalbano (@maramontalbano) has the story. 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.


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


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