Microbe processes carbon via new metabolic pathway

Jan 21, 2011 by Lin Edwards report

(PhysOrg.com) -- A Dead Sea microbe has been found to use a previously unknown metabolic pathway to metabolize fats as a source of carbon to synthesize carbohydrates. This suggests there may be other undiscovered pathways and more ways to live in extreme habitats than previously believed.

Every organism known metabolizes carbon compounds to produce energy and the basic cellular building blocks. Humans and other do this via the Krebs cycle, in which acetyl coenzyme A (acetyl-CoA) plays an important role.

Vertebrates are unable to convert acetyl-CoA into malate, a precursor of other molecules such as sugars, but many plants and microorganisms can, via either the glyoxylate cycle or the ethylmalonyl-CoA pathway, which was discovered in 2007 by a team of scientists led by Dr. Ivan A. Berg of the University of Freiburg in Germany. The new microbe, a single-celled microorganism of the domain Archaea, was discovered by the same research team to use a third pathway that was previously unknown.

The researchers realized the microbe could not use the glyoxylate cycle because an essential enzyme in the cycle, isocitrate lyase, was missing. It could not use the ethylmalonyl-CoA pathway either because it lacks some of the genes necessary to synthesize the enzymes used in the cycle.

Over a period of two years the researchers analyzed the enzymes H. marismortui used when it was grown on a medium containing and determined it was using the methylaspartate cycle (named after an intermediate in the cycle to convert acetyl-CoA to malate. This cycle is longer and more complex than the other two pathways but it does have advantages for a microbe living in such salty conditions, since one of the intermediates in the cycle limits , which would draw water out of the cell in attempt to balance the across the cell membrane.

Dr. Berg said the discovery of the third means there could be others, and added that “the diversity of life is bigger than we know now.”

The discovery also sheds some light on evolutionary processes since the enzymes in the cycle are similar to those found in ancient bacteria, but are not present in other Archaea, which suggests H. marismortui’s ancestors obtained the genes by lateral gene transfer rather than evolving through a lengthy series of random mutations. Berg said there were few such examples where it is so clear how the metabolic pathway evolved, which he said makes the pathway “a kind of a wonder.”

Explore further: Team publishes evidence for natural alternative to antibiotic use in livestock

More information: A Methylaspartate Cycle in Haloarchaea, Science 21 January 2011: Vol. 331 no. 6015 pp. 334-337. DOI:10.1126/science.1196544

Related Stories

New insights into the origin of life on Earth

Dec 11, 2006

In an advance toward understanding the origin of life on Earth, scientists have shown that parts of the Krebs cycle can run in reverse, producing biomolecules that could jump-start life with only sunlight and a mineral present ...

Recommended for you

Researchers capture picture of microRNA in action

Oct 30, 2014

Biologists at The Scripps Research Institute (TSRI) have described the atomic-level workings of "microRNA" molecules, which control the expression of genes in all animals and plants.

Blocking a fork in the road to DNA replication

Oct 30, 2014

A team of Whitehead Institute scientists has discovered the surprising manner in which an enigmatic protein known as SUUR acts to control gene copy number during DNA replication. It's a finding that could shed new light on ...

Cell division, minus the cells

Oct 30, 2014

(Phys.org) —The process of cell division is central to life. The last stage, when two daughter cells split from each other, has fascinated scientists since the dawn of cell biology in the Victorian era. ...

A new method simplifies the analysis of RNA structure

Oct 30, 2014

To understand the function of an RNA molecule, similar to the better-known DNA and vital for cell metabolism, we need to know its three-dimensional structure. Unfortunately, establishing the shape of an RNA ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Negative
not rated yet Jan 21, 2011
"Microbe processes carbon via new metabolic pathway"

new? really???

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.