Humans and our ancestors have evolved since the most ancient times with a commensal microbiota. The conservation of indicator species in a niche-specific manner across all of the studied human population groups suggests that the microbiota confer conserved benefits on humans. Nevertheless, certain of these organisms have pathogenic properties and, through medical practices and lifestyle changes, their prevalence in human populations is changing, often to an extreme degree. In this Essay, we propose that the disappearance of these ancestral indigenous organisms, which are intimately involved in human physiology, is not entirely beneficial and has consequences that might include post-modern conditions such as obesity and asthma.
"Similar improvement in host fitness has been reported for insects, in which endosymbiotic species of Burkholderia are acquired horizontally every generation (Kikuchi et al., 2007). Even in humans it has been shown that the disappearance of ancestral indigenous commensal microbiota, which is intimately involved in human physiology, is not beneficial and may have many health consequences (Sears, 2005; Blaser and Falkow, 2009). Protective mutualism conferred by horizontally transmitted microbes has been poorly studied in plants (except for mycorrhizal or rhizobial associations), especially in their native environments (Evans et al., 2003; Berlec, 2012). "
[Show abstract][Hide abstract] ABSTRACT: It has been shown that the disappearance of, or drastic changes in, ancestral and indigenous (or native) endosymbiotic microbiota can lead to many adverse health consequences. However, the effects of changes in beneficial endosymbionts in plants are poorly known (except for mycorrhizal and rhizobial associations). We sampled and compared endophytes from hundreds of trees belonging to the economically important genus Hevea, the source of natural rubber, in their native range in the Amazon basin and in plantations. We also conducted antagonism tests to determine the potential effects that some of these endophytes may have on selected plant pathogenic fungi. The natural and indigenous endosymbiotic mycota of the rubber tree (Hevea) contains a high diversity of beneficial fungi that may protect against pathogens (protective mutualism). In contrast, plantation trees have a reduced and different diversity of these beneficial fungi. We propose that abundance, and not just presence, of competitive fungal strains and species (i.e., Trichoderma and Tolypocladium) create a protective effect against pathogens in wild trees. This study provides support for the importance of mutualistic endosymbionts in plant health and ecosystem resilience, and calls for awareness of their potential loss by human-related activities.
"Co-habitation in humans leads to sharing of microbiota, which is enhanced when dogs also co-habit in the same house (Song et al., 2013). Ironically, hygiene measures aimed at reducing pathogen transmission may have had broad negative impacts on the transmission of commensals and may underlie the loss of diversity observed in the West (Blaser and Falkow, 2009). Who Are They? "
"A Helicobacter-macacae-like OTU was also exclusively detected in PNG samples as a core member. Deliberate eradication of Helicobacter pylori has led to a significant reduction of this species in westernized countries (Blaser and Falkow, 2009), and other species of this genus might also have been affected. However, PNGspecific core OTUs were not detected in data sets from other non-westernized samples and we therefore cannot conclude that they represent members of an ancestral microbiome. "
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