Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Newfound gene may help bacteria survive in extreme environments

26.07.2012
Resulting microbial lipids may also signify oxygen dips in Earth's history

In the days following the 2010 Deepwater Horizon oil spill, methane-eating bacteria bloomed in the Gulf of Mexico, feasting on the methane that gushed, along with oil, from the damaged well. The sudden influx of microbes was a scientific curiosity: Prior to the oil spill, scientists had observed relatively few signs of methane-eating microbes in the area.

Now researchers at MIT have discovered a bacterial gene that may explain this sudden influx of methane-eating bacteria. This gene enables bacteria to survive in extreme, oxygen-depleted environments, lying dormant until food — such as methane from an oil spill, and the oxygen needed to metabolize it — become available. The gene codes for a protein, named HpnR, that is responsible for producing bacterial lipids known as 3-methylhopanoids. The researchers say producing these lipids may better prepare nutrient-starved microbes to make a sudden appearance in nature when conditions are favorable, such as after the Deepwater Horizon accident.

The lipid produced by the HpnR protein may also be used as a biomarker, or a signature in rock layers, to identify dramatic changes in oxygen levels over the course of geologic history.

"The thing that interests us is that this could be a window into the geologic past," says MIT postdoc Paula Welander, who led the research. "In the geologic record, many millions of years ago, we see a number of mass extinction events where there is also evidence of oxygen depletion in the ocean. It's at these key events, and immediately afterward, where we also see increases in all these biomarkers as well as indicators of climate disturbance. It seems to be part of a syndrome of warming, ocean deoxygenation and biotic extinction. The ultimate causes are unknown."

Welander and Roger Summons, a professor of Earth, atmospheric and planetary sciences, have published their results this week in the Proceedings of the National Academy of Sciences.

A sign in the rocks

Earth's rocky layers hold remnants of life's evolution, from the very ancient traces of single-celled organisms to the recent fossils of vertebrates. One of the key biomarkers geologists have used to identify the earliest forms of life is a class of lipids called hopanoids, whose sturdy molecular structure has preserved them in sediment for billions of years. Hopanoids have also been identified in modern bacteria, and geologists studying the lipids in ancient rocks have used them as signs of the presence of similar bacteria billions of years ago.

But Welander says hopanoids may be used to identify more than early life forms: The molecular fossils may be biomarkers for environmental phenomena — such as, for instance, periods of very low oxygen.

To test her theory, Welander examined a modern strain of bacteria called Methylococcus capsulatus, a widely studied organism first isolated from an ancient Roman bathhouse in Bath, England. The organism, which also lives in oxygen-poor environments such as deep-sea vents and mud volcanoes, has been of interest to scientists for its ability to efficiently consume large quantities of methane — which could make it helpful in bioremediation and biofuel development.

For Welander and Summons, M. capsulatus is especially interesting for its structure: The organism contains a type of hopanoid with a five-ring molecular structure that contains a C-3 methylation. Geologists have found that such methylations in the ring structure are particularly well-preserved in ancient rocks, even when the rest of the organism has since disappeared.

Welander pored over the bacteria's genome and identified hpnR, the gene that codes for the protein HpnR, which is specifically associated with C-3 methylation. She devised a method to delete the gene, creating a mutant strain. Welander and Summons then grew cultures of this mutant strain, as well as cultures of wild, unaltered bacteria. The team exposed both strains to low levels of oxygen and high levels of methane over a two-week period to simulate an oxygen-poor environment.

During the first week, there was little difference between the two groups, both of which consumed methane and grew at about the same rate. However, on day 14, the researchers observed the wild strain begin to outgrow the mutant bacteria. When Welander added the hpnR gene back into the mutant bacteria, she found they eventually bounced back to levels that matched the wild strain.

Just getting by to survive

What might explain the dramatic contrast in survival rates? To answer this, the team used electron microscopy to examine the cellular structures in both mutant and wild bacteria. They discovered a stark difference: While the wild type was filled with normal membranes and vacuoles, the mutant strain had none.

The missing membranes, Welander says, are a clue to the lipid's function. She and Summons posit that the hpnR gene may preserve bacteria's cell membranes, which may reinforce the microbe in times of depleted nutrients.

"You have these communities kind of just getting by, surviving on what they can," Welander says. "Then when they get a blast of oxygen or methane, they can pick up very quickly. They're really poised to take advantage of something like this."

The results, Welander says, are especially exciting from a geological perspective. If 3-methylhopanoids do indeed allow bacteria to survive in times of low oxygen, then a spike of the related lipid in the rock record could indicate a dramatic decrease in oxygen in Earth's history, enabling geologists to better understand periods of mass extinctions or large ocean die-offs.

"The original goal was [to] make this a better biomarker for geologists," Welander says. "It's very meticulous [work], but in the end we also want to make a broader impact, such as learning how microorganisms deal with hydrocarbons in the environment."

This research was supported by NASA and the National Science Foundation.

Written by Jennifer Chu, MIT News Office

Caroline McCall | EurekAlert!
Further information:
http://www.mit.edu

More articles from Life Sciences:

nachricht 3D technology lets us look into the distant past
20.05.2019 | Eberhard Karls Universität Tübingen

nachricht Dangerous pathogens use this sophisticated machinery to infect hosts
20.05.2019 | California Institute of Technology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Self-repairing batteries

UTokyo engineers develop a way to create high-capacity long-life batteries

Engineers at the University of Tokyo continually pioneer new ways to improve battery technology. Professor Atsuo Yamada and his team recently developed a...

Im Focus: Quantum Cloud Computing with Self-Check

With a quantum coprocessor in the cloud, physicists from Innsbruck, Austria, open the door to the simulation of previously unsolvable problems in chemistry, materials research or high-energy physics. The research groups led by Rainer Blatt and Peter Zoller report in the journal Nature how they simulated particle physics phenomena on 20 quantum bits and how the quantum simulator self-verified the result for the first time.

Many scientists are currently working on investigating how quantum advantage can be exploited on hardware already available today. Three years ago, physicists...

Im Focus: Accelerating quantum technologies with materials processing at the atomic scale

'Quantum technologies' utilise the unique phenomena of quantum superposition and entanglement to encode and process information, with potentially profound benefits to a wide range of information technologies from communications to sensing and computing.

However a major challenge in developing these technologies is that the quantum phenomena are very fragile, and only a handful of physical systems have been...

Im Focus: A step towards probabilistic computing

Working group led by physicist Professor Ulrich Nowak at the University of Konstanz, in collaboration with a team of physicists from Johannes Gutenberg University Mainz, demonstrates how skyrmions can be used for the computer concepts of the future

When it comes to performing a calculation destined to arrive at an exact result, humans are hopelessly inferior to the computer. In other areas, humans are...

Im Focus: Recording embryonic development

Scientists develop a molecular recording tool that enables in vivo lineage tracing of embryonic cells

The beginning of new life starts with a fascinating process: A single cell gives rise to progenitor cells that eventually differentiate into the three germ...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

SEMANTiCS 2019 brings together industry leaders and data scientists in Karlsruhe

29.04.2019 | Event News

Revered mathematicians and computer scientists converge with 200 young researchers in Heidelberg!

17.04.2019 | Event News

First dust conference in the Central Asian part of the earth’s dust belt

15.04.2019 | Event News

 
Latest News

Cement as a climate killer: Using industrial residues to produce carbon neutral alternatives

20.05.2019 | Materials Sciences

When bees are freezing

20.05.2019 | Life Sciences

Machine learning speeds modeling of experiments aimed at capturing fusion energy on Earth

20.05.2019 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>