Development in Bacterial Genomic Size.
Genome is the totality of hereditary information of any organism in the decoded form. In molecular biology and genetics, today genome is the only tool which is helping in its development. As compared to genomes of animals and single cell eukaryotes, the size of the microbial genomes like bacteria is very less. The ranges of bacterial genome are from 130 kbp to 12500 kbp. The hereditary information is encoded either in the form of DNA or RNA. Many virus contains there genomic information within the RNA only. The non-coding sequence of the DNA as well as RNA along with genes forms genome. Today with the development in DNA sequencing technology, the correlation between the number of genes and the size of genome has been established. It is today known that the size of genome of bacteria is very small. There is small amount of DNA in the very compact form within the single cell bacteria.
Once research by scientist Cole et al had proved that with the evolution, there is large proportion of gene decay when compared with Leprosy bacillus to ancestral bacteria. Due to this degradation in genome, the genome size has gone down as compared to their ancestors. Many researches in this field are today also going on to find out the genome decay process as well as the method by which such decay happens. Many a times it has been found that this is due to deletion. It has also been found that many pathogens are exception to this degradation and may be one of the reasons for their pathogenicity. In Leprosy bacillus, the pseudo genes were higher than functional genes as compared to that found in their living ancestors.
As compared to genome size of major groups of life, the genome size within the various bacterial species is having little variation. In eukaryotic cells, the genome size is less relevance considering the number of functional genes than in eukaryotic species. This relation of genome size and number of genes in bacteria makes this subject interesting for research and scientific discussion. The evolution tells us that the bacteria were free living organism. During the course of evolution some bacteria become pathogens while some remain symbiotic. It has also been found that free living microorganisms are having largest genome out of the three other types of bacteria. The bacteria which have acquired the pathogenicity recently have fewer pseudogenes. Therefore it can be said that as like the lifestyle of humans affects their health, the lifestyle or environment in which bacteria live affects their genome size. Many recently developed pathogens and facultative microorganisms have smaller genome size than other free living organisms. In spite of this they have more number of pseudogenes as compared to any other form of bacteria. In case of obligate bacteria, they have smallest genome and the less number of pseudogenes irrespective of either they are symbionts or pathogens. Today the research is working on the question of relationship between life style of bacteria and its genome size.
But with the development of science and research today we are able to find out the facts which were hidden for several years may it be from smaller life not only like the size of bacteria but also from sizes lesser than it or may be it like hidden facts related to the genomic and to the lifestyle!
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