We also use bioinformatic approaches to glean evolutionary histories from bacterial genome data. Horizontal transfer has had a tremendous impact in the evolution of enteric bacterial genomes. We have developed biostatistical measures that can predict the rate of horizontal transfer based on genome sequence signatures. The introduction of novel functions by horizontal transfer, like the cob and pdu operons into Salmonella, allow rapid expansion into new niches. Saltation in phenotypic states may provide the environmental separation necessary for bacterial speciation.
Bacterial genomes have long been considered streamlined, that is reduced in size for rapid growth.
Yet natural variation in genome size within a species and the propensity for large duplications in growing strains both belie this conclusion. Rather, it is likely that bacterial genomes may be as large as is possible for a species to maintain, depending on its effective population size. Alternative pathways for siroheme biosynthesis in Klebsiella aerogenes . Methionine to cysteine recycling in Klebsiella aerogenes . The origins and ongoing evolution of viruses.