Genome complexity: Smallest gene count for life (Introduction)

by David Turell , Friday, March 25, 2016, 00:28 (2954 days ago) @ David Turell

Scientists, by knocking out genes, have cultured a living bacterium with a probably the smallest number of genes and live:-http://phys.org/news/2016-03-microbe-stripped-down-dna-hint-secrets.html-"Scientists have deleted nearly half the genes of a microbe, creating a stripped-down version that still functions, an achievement that might reveal secrets of how life works.-***-"The newly created bacterium has a smaller genetic code than does any natural free-living counterpart, with 531,000 DNA building blocks containing 473 genes.-***-"But even this stripped-down organism is full of mystery. Scientists say they have little to no idea what a third of its genes actually do.-"We're showing how complex life is, even in the simplest of organisms," researcher J. Craig Venter told reporters. "These findings are very humbling."-***-"The genome is not some one-and-only minimal set of genes needed for life itself. For one thing, if the researchers had pared DNA from a different bacterium they would probably have ended up with a different set of genes. For another, the minimum genome an organism needs depends on the environment in which it lives.-"And the new genome includes genes that are not absolutely essential to life, because they help the bacterial populations grow fast enough to be practical for lab work.-"The genome is "as small as we can get it and still have an organism that is ... useful," Hutchison said.-***-"The work began with a manmade version of a microbe that normally lives in sheep, called M. mycoides (my-KOY'-deez). It has about 900 genes. The scientists identified 428 nonessential genes, built their new genome without them, and showed that it was complete enough to let a bacterium survive.-Experts not involved with the work were impressed.-"'I find this paper really groundbreaking," said Jorg Stulke of the University of Goettingen in Germany, who is working on a similar project with a different bacterium. In an email, he said the researchers seem to have gotten at least very close to a minimum genome for M. mycoides."-Comment: Venter's point is very important. It emphasizes how difficult it is to originate life.