A team of researchers has found in the depths of Yellowstone’s hot springs a type of unique photosynthesizing bacterium that is considered to belong to a new genus and species.
Founded by the National Science Foundation, the research provides further insight into how diverse the Yellowstone ecosystem is and how useful it can be for practical exploration. The results are published in the July 27, 2007, issue of Science in a paper led by Don Bryant of Penn State University and David M. Ward of Montana State University.
The odd bacterium has been named Candidatus chloracidobacterium ( Cab. ) thermophilum, and although scientists agree that it belongs to a new genus and species, it is also considered to be a part of Acidobacteria phylum, a poorly characterized phylum that was not previously known to include bacteria capable of photosynthesis. In biological taxonomy, a phylum is a taxon in the rank below kingdom and above class.
Researchers got the idea for their study from the fact that Yellowstone National Park is the world’s largest scientific reservoir that harbors what may be the world's largest diversity of thermophilic ( heat-loving ) microorganisms.
"Cab. thermophilum is the first photosynthesizing bacterium discovered in the Acidobacteria phylum," said Ronald Weiner, program director in NSF's Division of Molecular and Cellular Biosciences.
Chlorophyll-producing bacteria are so abundant that they perform half the photosynthesis on Earth. But only five of the 25 major groups, or phyla, of bacteria previously were known to contain members with this ability.
"The microbial mats give the hot springs in Yellowstone their remarkable yellow, orange, red, brown and green colors," says Bryant. Microbiologists are intrigued by Yellowstone's hot springs "because their unusual habitats house a diversity of microorganisms, but many are difficult or impossible to grow in the lab. Metagenomics has given us a powerful new tool for finding these hidden organisms and exploring their physiology, metabolism, and ecology."
Metagenomics (also Environmental Genomics, Ecogenomics or Community Genomics) is the study of genomes recovered from environmental samples as opposed to from clonal cultures, or, simply put, a means of studying organisms without having to culture them.
Bulk samples are collected from the environment, then DNA is isolated from the cells and sequenced by so-called shotgun sequencing on a very large scale. Analysis of the DNA sequences reveals what types of genes and organisms are present in the environment.
Cab. Thermopillum was found to live near the surface of the mats along with the green-blue algae, or cyanobacteria, at a temperature of about 50 to 66 degrees Celsius ( 122 to 151 degrees Fahrenheit ), where it could use light and oxygen.
The weird thing about Cab. Thermophillum was the discovery of some special light-harvesting antennae known as chlorosomes, which each contain about 250,000 chlorophylls. Researchers concluded Cab. Thermophillum belongs to a new species because no member of its potential phylum (Acidobacteria), or any aerobic microbe was known to make chlorosomes before this discovery.
"This is an excellent example of how metagenic information reveals how little we know about life on Earth," said Weiner.
"Finding a previously unknown, chlorophyll-producing microbe is the discovery of a lifetime for someone who has studied bacterial photosynthesis for as long as I have ( 35 years )," says Bryant. "I wouldn't have been as excited if I had reached into that mat and pulled out a gold nugget the size of my fist!"