AMHERST, Mass. - A team of scientists at the University of Massachusetts led by microbial genetics professor Shiladitya DasSarma, in collaboration with noted molecular biotechnologist Leroy Hood of the Institute of Systems Biology (ISB), Seattle, Wash., has completed the genome sequence of Halobacterium species NRC-1, an "extremophilic" microorganism that grows best in an environment 10 times saltier than sea water. The achievement will be published in the Oct. 3 edition of the journal Proceedings of the National Academy of Sciences (PNAS).
This not only is the first genome project completed at UMass, according to University researchers, but the first genome of any halophile (salt-loving microbe) and one of the first of several dozen genome projects of whole organisms ever completed, according to The Institute for Genomic Research.
"Genome studies on Halobacterium should contribute toward some of the greatest unsolved mysteries of biology today, including our understanding of evolution as well as of the fundamental life process in higher cells," says DasSarma. "There is a tremendous genetic resource in the genomes of microorganisms. In fact, it is one of the last, largely untapped, natural resources on our planet."
DasSarma and Hood led a consortium of researchers from 12 universities and research centers in the U.S., Canada, and the U.K., on the three-year, $1.2-million project funded by the National Science Foundation (NSF). Participating institutions included Stanford University, University of Wisconsin, University of Pennsylvania, and the Marine Biological Laboratory at Woods Hole, Mass.
Halobacterium NRC-1 is a member of the archaea, the third branch of life in the biological world. Archaea are evolutionary relics, microorganisms that are among the most ancient forms of life, yet they represent a third of all living creatures. Astronomical numbers of Halobacterium—which are microscopic, rod-shaped organisms—can be found in bodies of very salty water, including the Great Salt Lake and the Dead Sea. The single-celled organism utilizes sunlight to synthesize energy, giving off a red byproduct, and has been harvested for commercial use for its light-sensitive properties. When a body of water turns bright pink or red, it is often a sign that millions of halobacteria are present. These microorganisms, and their red pigment, can remain in salt crystals left behind long after a lake dries up.
"The Halobacterium genome is one of the first and only genetically tractable archaea to be sequenced. As such, it represents the key to both unlocking the scientific mysteries of archaea and opening avenues of practical use of our natural genetic resources," says DasSarma.
According to DasSarma, this particular genome will serve as an excellent model for all organisms in the archaeon. "Some aspects of the biology of Halobacterium resemble higher cells called eukaryotes, especially the means by which cells turn genes on or off. An understanding of this genome will help us learn how cells regulate genes. We have not observed such a sophisticated regulatory network in such a primitive organism before."
DasSarma says that a handful of organisms in the archaea have been sequenced before, but this is the first halophile, or salt-loving organism. Because they can live under extreme conditions, Halobacterium are easy to culture. And, because they are completely harmless to humans, the study of this genome can be useful for teaching biological principles in colleges and schools, according to the UMass microbiologist.
DasSarma adds: "These tiny creatures will provide many insights into how more complex creatures manage life functions, including cell division, and the way cells transport proteins across biological membranes. Right now, several biomedical applications using Halobacterium are being investigated, including the development of orally administered vaccines, and the design of new antibiotics."
NSF program director Joanne Tornow says the foundation''s goal is to catalyze the development of similar genomic research. "Genomic projects have produced a great deal of data, but we''re just getting to the point where we can find answers to a lot of the most interesting biology questions," she said. "Every day, we learn more about functional, comparative, and structural genomics. This data will allow us to ask questions we couldn''t ask before."
Leroy Hood may be best known as the creator of DNA sequencing technology. Forty-three researchers, including the team leaders, participated in producing the manuscript outlining their findings. Wailap Victor Ng, a UMass alumnus currently on the faculty of ISB, was first author of the manuscript.