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Category: Fungi and Fungal Pathogenesis; Bacterial Pathogenesis
Evolution of Helicobacter and Helicobacter Infections, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555815639/9781555814144_Chap37-1.gif /docserver/preview/fulltext/10.1128/9781555815639/9781555814144_Chap37-2.gifAbstract:
Skin, ears, eyes, vagina, mouth, and gastrointestinal mucosa are colonized with diverse microbial communities of bacteria, archaea, fungi, protozoa, and helminths. We know little about these colonizers and even less about the indigenous viruses and their ecologic role in microbial communities. Mechanisms that may permit lactic acid bacteria to reduce intestinal infections include lowering the gut pH to inhibit competing pathogens, secretion of natural antibiotics (e.g., lactobacilli and bifidobacteria species), improved immune stimulation, and blocking of adhesion sites in the gut needed by the pathogens. Competition for resources in the face of host responses, population density, and strain dominance surely affect the evolution of Helicobacter pylori as well as the downstream risks of disease. Host physiology allows higher density and more diverse colonization in some parts of the body than in others. A list of Helicobacter species isolated from animals and humans is provided in this chapter. H. pylori has numerous strain-specific restriction-modification (RM) systems that vary in activity and are regulated by mutation and recombination. A list of restriction endonucleases isolated from three H. pylori strains is also provided in the chapter. Transformation and mutation are important sources of variation of H. pylori to provide genetic substrate to respond to selection forces. In total, through endogenous mutation and horizontal gene transfer H. pylori is capable of maintaining great variability that confers the ability to colonize numerous different gastric niches and to survive gastric changes.
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Ages of life on Earth.
Schematic representation of host resource utilization by H. pylori populations.
Biphasic interaction of a coevolved symbiont microbe and its host. In the postproductive period symbiosis involves the microbial-induced demise of the host. Although deleterious for the individual, it is beneficial for the group.
Helicobacter species isolated from animals and humans
Restriction endonucleases isolated from three H. pylori strains a