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Review
. 2015 Jan;8(1):9-22.
doi: 10.1111/eva.12231. Epub 2014 Nov 20.

Friend and foe: factors influencing the movement of the bacterium Helicobacter pylori along the parasitism-mutualism continuum

Derek Lin  1 , Britt Koskella  2
Affiliations
Review

Friend and foe: factors influencing the movement of the bacterium Helicobacter pylori along the parasitism-mutualism continuum

Derek Lin et al. Evol Appl. 2015 Jan.

Abstract

Understanding the transition of bacterial species from commensal to pathogen, or vice versa, is a key application of evolutionary theory to preventative medicine. This requires working knowledge of the molecular interaction between hosts and bacteria, ecological interactions among microbes, spatial variation in bacterial prevalence or host life history, and evolution in response to these factors. However, there are very few systems for which such broad datasets are available. One exception is the gram-negative bacterium, Helicobacter pylori, which infects upwards of 50% of the global human population. This bacterium is associated with a wide breadth of human gastrointestinal disease, including numerous cancers, inflammatory disorders, and pathogenic infections, but is also known to confer fitness benefits to its host both indirectly, through interactions with other pathogens, and directly. Outstanding questions are therefore why, when, and how this bacterium transitions along the parasitism-mutualism continuum. We examine known virulence factors, genetic predispositions of the host, and environmental contributors that impact progression of clinical disease and help define geographical trends in disease incidence. We also highlight the complexity of the interaction and discuss future therapeutic strategies for disease management and public health in light of the longstanding evolutionary history between the bacterium and its human host.

Keywords: antibiotic resistance; carcinogenic bacteria; gut microbiota; host–parasite coevolution; human health; microbiome; probiotics; virulence factors.

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Figures

Figure 1
Figure 1
Schematic summarizing the key genetic, ecological, and evolutionary factors known to influence the transition of Helicobacter pylori along the parasitism–mutualism continuum. Factors known to increase potential pathogenicity are in red, those that are involved in colonization and survival in the human host, but which have no direct evidence of conferring either cost or benefit to the host are in black, and factors that are thought to be associated with conferred benefits to the host (either directly or indirectly) are in green. Further factors that are predicted from theory but which have not been examined empirically are included in italics. Details of each association are discussed within the main text. References: (1) Oleastro and Ménard (2013); (2) Censini et al. (1996); (3) Maeda et al. (1998); (4) Persson et al. (2011); (5) Kodaman et al. (2014); (6) Gaddy et al. (2013); (7) Atherton et al. (1996); (8) León-Barúa et al. (2006); (9) Anderson and May (1982); (10) Eaton et al. (1992); (11) Ottemann and Lowenthal (2002); (12) Tsuda et al. (1994); (13) Gobert et al. (2001); (14) Bonis et al. (2010); (15) Salama et al. (2013); (16) Chen and Blaser (2007); (17) Arnold et al. (2011).
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