The Niche of<i>Escherichia coli</i>
ASM Press eBooks, Apr 9, 2014
This chapter presents an overview of the habitats where Escherichia coli can be isolated. It revi... more This chapter presents an overview of the habitats where Escherichia coli can be isolated. It reviews some of the data that characterize the boundaries of its broad ecological niche. The genus Escherichia is not as genetically diverse as once thought and contains only three named species: E. albertii, E. fergusonii, and E. coli. The frequency of gene flow among the phylogenetic lineages and the phylogenetic scale at which it is occurring suggest that boundaries to gene flow among Escherichia species are minimal and also that clades may not occupy entirely different ecological niches. The chapter discusses the niche of E. coli . A human host typically harbors two or three genotypes, and together these genotypes represent the majority of the E. coli cells to be found in a sample. First, nine or more genotypes may be detected in a sample at a single point in time. Second, selective plating reveals the presence of genotypes that exist at very low frequencies. Finally, the number of samples that contain rare genotypes also indicates that there may be a rather large pool of genotypes. The high densities of E. coli in sand led many to speculate that, as in the tropics and subtropics, E. coli is an environmental organism even in some of the coldest temperate regions. E. coli is widespread among warm-blooded animals and humans, and the dynamics of its colonization of the gastrointestinal (GI) tract is dependent on a number of host and microbial determinants.
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Papers by Elizabeth Alm