Scientists Explore Genome Of Methane-Breathing Microbe

TERRADAILY

Because of its unique characteristics, the bacteria Methylococcus capsulatus (above) has been attracting research interest since its discovery a couple of decades ago. As its name suggests, M. Capsulatus is a coccus, or roughly spherically shaped, encapsulated bacteria that is methanotrophic, or methane eating. Methanotropic bacteria can use simple organic materials, such as methane, the simplest of the hydrocarbons (CH4), together with certain minerals to make the building blocks of life (simple sugars, amino acids and fatty acids). Thus far, researchers have identified very few organisms capable of making these essential molecules. Most organisms, including us, need to ingest these basic molecuules in our diet or make them by breaking sown largerk, more complex molecules. The idea of an organism that naturally contains the biological pathways to make these fundamental molecules is very interesting. What can it tell us about the origins of life? What can it tell us about how to make such vitally important biological materials? How did it ever come to exist in such an extreme environment in the first place?

Rockville MD (SPX) Sep 22, 2004
The first complete genome sequence of a methane-breathing bacterium has revealed a surprising flexibility in its metabolism, suggesting an ability to live successfully in environments previously thought to be beyond its reach.

The genome sequence of Methylococcus capsulatus � a species typical of methane-breathing bacteria commonly found in soils, landfills, sediments and peat bogs � includes a full and at times redundant toolkit of genes for using methane as an energy and carbon source. Such methane-consuming microbes are called methanotrophs.

The study, to be published in the October issue of PLoS Biology and posted online this week, found an unexpected flexibility in M. capsulatus metabolic pathways, hinting that the bacterium is capable of responding to changes in its environment by functioning through different chemical pathways for using methane.

That finding, if confirmed by later experiments, may increase the bacterium's potential as a biotech workhorse.

Methanotrophs play an important role in the global energy cycle because they consume methane, a gas that is produced mostly by chemical processes in landfills, in the guts of ruminant livestock such as cows, and by oil and natural gas processing plants.

In recent years, environmental scientists have shown increasing interest in methanotrophs because their use of methane as a sole source of carbon and energy could possibly be harnessed to play an important role in efforts to reduce methane emissions that are generated by biological sources such as ruminants and landfills.

The PLoS Biology study found that M. capsulatus has multiple pathways for different stages in the oxidation of methane. They also found genes that suggest metabolic flexibility, including the microbe's likely ability to grow on sugars, to oxidize sulfur, and to live in reduced-oxygen environments.

"We now have a much better picture of the relationship between M. capsulatus and its environment," says Naomi Ward, the paper's first author. "It is important for us to know under what conditions methane can be removed from the ecosystem before it accumulates as a greenhouse gas."

Ward is an Assistant Investigator at The Institute for Genomic Research (TIGR), which led the genomic sequencing and conducted the analysis with scientific collaborators at the University of Bergen in Norway.

While noting that "there is a clear need for experimental validation" of the metabolic pathways suggested by the genome, the study's authors suggest that their analysis "deepens our understanding of methanotroph biology, its relationship to global carbon cycles, and its potential for biotechnological applications."

Johan Lillehaug, the Norwegian scientist who oversaw the University of Bergen's role in the project, says the genome analysis found that M. capsulatus has a novel strategy for scavenging copper, an essential element for regulating methane oxidation.

"We found that M. capsulatus is a good model for studying how microbes adapt to varying copper concentrations," he says, noting that M. capsulatus uses two separate systems � at high and low copper concentrations � for oxidizing methane.

Scientists say the organism's potential significance for biotechnology include the use of bacteriophage (viruses that infect bacteria) that have made a home in the genome. Such phages could be exploited to genetically manipulate M. capsulatus to more efficiently produce microbial protein for commercial animal feed.

The study's senior author, TIGR Investigator Jonathan Eisen, says the analysis of M. capsulatus also will help scientists learn more about some methane-fixing bacteria � those that live inside of animals such as clams and mussels in deep-sea methane seeps � that are extremely difficult to study. Such methane-fixing bacterial symbionts allow their host animals to feed off of the methane collected in seeps.

"The methane-fixing symbionts are very important ecologically but we know little about how they work since they live inside of animals and cannot be grown in pure cultures on their own,"says Eisen.

"Since the symbionts are closely related evolutionarily and biologically to Methylococcus capsulatus, we can now use the information gleaned from this genome sequence to make predictions about the symbionts."

TERRADAILY

Cold Sugar In Space Provides Clue To Molecular Origin Of Life

Socorro NM (SPX) Sep 21, 2004
Astronomers using the National Science Foundation's giant Robert C. Byrd Green Bank Telescope (GBT) have discovered a frigid reservoir of simple sugar molecules in a cloud of gas and dust some 26,000 light-years away, near the center of our Milky Way Galaxy.

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