Magazine article Science News

How Many Genes Does a Bacterium Need?

Magazine article Science News

How Many Genes Does a Bacterium Need?

Article excerpt

Take a look at today's bacteria. If push came to shove, how many of their genes could the microbes do without? Or to pose the query another way, what is the minimum number of genes sufficient for a modern bacterial cell?

In years past, such questions would have elicited replies no more scientific than calculations of how many angels can dance on the head of a pin. Yet in the last 15 months, researchers have unveiled the complete genetic complements of several single-celled organisms, including two bacteria. This new information has allowed investigators to take a serious stab at what were previously fanciful inquiries.

Relying largely upon a comparison of the bacteria whose full gene sets, or genomes, have been laid bare, two scientists now conclude that a mere 256 or so genes may be necessary and sufficient for the modern cell. Arcady R.

Mushegian and Eugene V. Koonin, both of the National Center for Biotechnology Information in Bethesda, Md., report their analysis in the Sept. 17

Proceedings of the National Academy of Sciences.

The researchers propose that determining the minimal genetic requirements of a modern single-celled organism may aid attempts to reconstruct the genome of the ancestral microorganism from which all current life presumably evolved. "Eventually, backwards extrapolation from the minimal gene set may lead close to the origin of life itself," Mushegian and Koonin write.

The two investigators constructed their minimal genome after examining the genes of Haemophilus influenzae and Mycoplasma genitalium, whose genomes were described last year (SN: 6/10/95, p. …

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