Origin of Life

Theories and evidence for chemical biopoieses

Minimal Genome

2001: Mycoplasma genitalium with 517 genes has the smallest gene complement of any independently replicating cell so far identified. Analysis suggests that 265 to 350 of the 480 protein-coding genes of M. genitalium are essential under laboratory growth conditions, including about 100 genes of unknown function. Science -- Abstracts: Hutchison et al. 286 (5447): 2165

2002: Here we show evidence of six species with a genome size smaller than Mycoplasma genitalium, the smallest bacterial genome reported thus far (580 kb). Our findings strongly suggest that the Buchnera genome is still experiencing a reductive process toward a minimum set of genes necessary for its symbiotic lifestyle. Extreme genome reduction in Buchnera spp.: Toward the minimal ...

2001: 2001: Genome Biology Full text The complexity of simplicity

Another Minimal Genome: Microbe Needs Just 271 Genes : Free Full Text : Modified: "A minimal genome is the smallest set of genes that an organism needs to live in a particular environment. While most microbes have hundreds or thousands of genes, some use only a fraction of these at any one time, depending on their surroundings."

The bacterium Bacillus subtilis needs just 271 genes to live in an experimental environment that is rich in nutrients, a new study has found. The calculated minimum of 271 genes is a small fraction of the organism's roughly 4,100 genes. To arrive at the number 271, the researchers grew thousands of B. subtilis cells and systematically inactivated one gene per cell.

The ideal test of a minimal genome would be to inactivate every non-essential gene in a single cell, but the technology to accomplish this does not yet exist. The vast majority of essential genes in B. subtilis belong to one of five categories, such as “information processing” and “protein synthesis.” Only a few essential genes could not be categorized because so little was known about them.

“One of the interesting aspects of the study was that we found so few essential genes of unknown function,“ says Dusko. “This shows that there are fewer holes in our understanding of the living cell than early studies led us to believe.”

Researchers hope ultimately to construct a minimal genome, using information about different microbes. Hundreds of "essential" genes in bacteria have been identified in recent years, providing a rough idea of what minimal genomes might look like.

The minimal genomes published to date range in number from about 260 genes to 670 genes, depending upon the organism, the environment in which it grows, and the strategy used to calculate which genes are essential."

Kobayashi, K. et al. Essential Bacillus subtilis genes. Proc Natl Acad Sci USA 100, 4678-4683 (April 15, 2003).

2005 : PEC (Profiling of E.coli Chromosome) : 250 genes minimal : 3,262,049 bp - genome map
: 3,262,049 bp - genome map

GENETICS:Ethical Considerations in Synthesizing a Minimal Genome -- Cho et al. 286 (5447): 2087 -- Science: "Researchers are attempting to model and eventually to create 'minimal organisms,' organisms with the smallest set of genes that allow for survival and reproduction. Although the ability to create such an organism is beyond current technology, the work of Hutchison et al., reported in this issue, represents an important step in the path toward the creation of such an organism. Here we identify ethical, social, and religious issues raised by this research. Issues discussed include the potential abuse of the technology (biological weapons, environmental problems), as well as the challenge it poses to our conception of the meaning of life."

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