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HSC scientists develop technique to disrupt genes in simplest cell (6-4-99)

Microbiologists here are reporting a fundamental breakthrough--disruption of gene function in the simplest self-reproducing cell known to science. The cell, called Mycoplasma genitalium, causes several human health problems including urethritis and arthritis, and has been implicated in Gulf War Illnesses. Understanding gene function in this disease-causing bacterium could lead to better diagnostic tools and treatments.

"This little guy consists of fewer than 470 genes," said Joel B. Baseman, Ph.D., professor and chair of the Department of Microbiology at The University of Texas Health Science Center at San Antonio. "It is one-eighth the size of the E. coli bacterium in terms of its genetic machinery. We are reporting the first direct gene knockout of the smallest self-replicating cell."

For purposes of comparison, the most complex life-form on earth, the human being, is made up of billions of cells each containing an estimated 100,000 genes.

Scientists use the term "gene knockout" to indicate that the expression or activity of a gene has been disrupted. "Mycoplasmas are excellent model systems for study of gene function because of their extreme simplicity," Dr. Baseman said. "Others have tried to do what we have done, but failed."

The technique is called Targeted Gene Disruption Through Homologous Recombination. It involves introducing a plasmid--or extrachromosomal DNA--into M. genitalium to disrupt function of a specific gene called mg218.

The work is described in the April 1999 Proceedings of the National Academy of Sciences. Authors from the Health Science Centerís microbiology department are Subramanian Dhandayuthapani, Ph.D., assistant professor (lead author); Wanda G. Rasmussen, research associate; and Dr. Baseman.

Contact: Will Sansom