Genome content

The first thing that we note is that there is a lot of variation in genome content within individual phyla. Consider the birds for example. At one extreme, there are birds that have genomes containing 700 million (7x10 ) nucleotide base pairs and at the other extreme there are some that contain 2 billion (2 x 10 ) base pairs, a variation of about a factor of three. The variation is considerably greater for the amphibians 600 million base pairs at one end of the spectrum to 80 billion (8 x 10 ) at the other end. 

The two ways genome content may be reported are in absolute amounts and in arbitrary units. When expressing genome size in absolute terms, various units may be employed. The most common unit is pico-grams (1 pg is equal to 10 12 g). Other units that may be used are daltons and nucleotide pairs. One is able to convert from one unit to another based on the following equations 1 nucleotide pair = 660 daltons, and 1 pg = 0.965 X 109 nucleotide pairs. It should be noted that these conversions are only estimates and should be considered accordingly. 

Comparative genomic hybridization analyses have contributed greatly to our understanding of bacterial evolution, population genetics, and pathogenesis. Here, we describe a robust protocol for microarray-based comparison of genome content, which could be applied to any bacterial species of interest. 

The reference strain is representative of one of the sequenced strains encoded on the microarray, and the test strain represents a strain of unknown genomic content. 

Sequencing Technique that elucidates the sequence of the molecules that form an organism s genomic content... 

The behavior of strains is therefore linked to their genomic content but, although the mechanisms are not yet known, it also depends on the nature of the other strains (and cratainly species) sharing the same ecosystem. 

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