<P> Bacterial genomes are generally smaller and less variant in size among species when compared with genomes of animals and single cell eukaryotes . Bacterial genomes can range in size anywhere from about 130 kbp to over 14 Mbp . A study that included, but was not limited to, 478 bacterial genomes, concluded that as genome size increases, the number of genes increases at a disproportionately slower rate in eukaryotes than in non-eukaryotes . Thus, the proportion of non-coding DNA goes up with genome size more quickly in non-bacteria than in bacteria . This is consistent with the fact that most eukaryotic nuclear DNA is non-gene coding, while the majority of prokaryotic, viral, and organellar genes are coding . Right now, we have genome sequences from 50 different bacterial phyla and 11 different archaeal phyla . Second - generation sequencing has yielded many draft genomes (close to 90% of bacterial genomes in GenBank are currently not complete); third - generation sequencing might eventually yield a complete genome in a few hours . The genome sequences reveal much diversity in bacteria . Analysis of over 2000 Escherichia coli genomes reveals an E. coli core genome of about 3100 gene families and a total of about 89,000 different gene families . Genome sequences show that parasitic bacteria have 500--1200 genes, free - living bacteria have 1500--7500 genes, and archaea have 1500--2700 genes . A striking discovery by Cole et al. described massive amounts of gene decay when comparing Leprosy bacillus to ancestral bacteria . Studies have since shown that several bacteria have smaller genome sizes than their ancestors did . Over the years, researchers have proposed several theories to explain the general trend of bacterial genome decay and the relatively small size of bacterial genomes . Compelling evidence indicates that the apparent degradation of bacterial genomes is owed to a deletional bias . </P> <P> As of 2014, there are over 30,000 sequenced bacterial genomes publicly available and thousands of metagenome projects . Projects such as the Genomic Encyclopedia of Bacteria and Archaea (GEBA) intend to add more genomes . </P> <P> The single gene comparison is now being supplanted by more general methods . These methods have resulted in novel perspectives on genetic relationships that previously have only been estimated . </P> <P> A significant achievement in the second decade of bacterial genome sequencing was the production of metagenomic data, which covers all DNA present in a sample . Previously, there were only two metagenomic projects published . </P>

How many base pairs in a bacterial genome