Genome Sequencing
Genome SequencingGenome Sequencing
Microbiology has entered the realm of genome sequencing. This biological revolution is opening up new dimensions in our view of life.
In 1995, a report on the entire DNA sequence for the genome of the bacteria Haemophilus influenzae was published . Although the genomes for a number of viruses had been completed before this, H. influenzae was the first free-living organism to have it's genome sequenced, and as such, this report remains a biological milestone. Since then, the entire genome sequences for over 10 microorganisms have been compiled and released and more are on their way. The completed microbial genomes include:
Haemophilus influenzae finished 1995
Mycoplasma genitalium finished 1995
Methanococcus jannaschii finished 1996
Synechocystis sp. finished 1996
Mycoplasma pneumoniae finished 1996
Saccharomyces cerevisiae finished 1997
Helicobacter pylori finished 1997
Escherichia coli finished 1997
Bacillus subtilis finished 1997
Archaeoglobus fulgidus finished 1997
The benefits of complete genome sequencing projects include a greater understanding of the organisms being sequenced and acknowledgment of the minimum complement of genes necessary for a free-living organism. Of the organisms that have already had their genomes sequenced, a number are of particular importance. For example, Mycoplasma genitalium has a complete nucleotide sequence that is only 580,070 base pairs long, and as such, is believed to be the smallest genome of any free-living organism. Because of it's unique size, this genome presents a way of studying a minimal functional gene set. In addition, complete genome sequencing projects are currently being carried out on a number of microbial pathogens in an attempt to better understand them. The inference of molecular structures, in particular genome sequences, have direct practical consequences in clinical microbiology. Data and analyses of clinically important microorganisms are being used to develop molecular diognostics as well as to guide research in the nature of these organisms. Information obtained from sequencing is also being used to provide enzymes for biotechnical and industrial applications.
The impact that genome sequencing has had, and will have, on our view of life only begins here. It appears that the time has come to move formal taxonomy and phylogenetic classification into line with the system emerging from molecular data.
Prior to the 1960's, evolutionary study had been confined to multicellular eucaryotes whose histories, at best, only cover about 20% of the total evolutionary time span. Plants and animals have complex morphologies, which served as the basis for their phylogenetic classification. In contrast, bacteria have morphologies that are too simple to be used in this way. Many early microbiologists avoided the area of phylogenetic classification for this reason, despite the fact that the history of the microbial world spans most of the Earth's existence. Those who did study the discipline created distorted schemes that are now under review.
Since the 1950's, molecular studies have been used to determine evolutionary relationships, although microbiology remained blind to the potential of this unique approach until rRNA sequences were shown to provide a key to procaryotic phylogeny in the 1970's. It would appear that genome sequencing has advanced the science...
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