On the effect of inheritance of microbes in commensal microbiomes

Abstract

Background Our current view of nature depicts a world where macroorganisms dwell in a landscape full of microbes. Some of these microbes not only transit but establish themselves in or on hosts. Although hosts might be occupied by microbes for most of their lives, a microbe-free stage during their prenatal development seems to be the rule for many hosts. The questions of who the first colonizers of a newborn host are and to what extent these are obtained from the parents follow naturally. Results We have developed a mathematical model to study the effect of the transfer of microbes from parents to offspring. Even without selection, we observe that microbial inheritance is particularly effective in modifying the microbiome of hosts with a short lifespan or limited colonization from the environment, for example by favouring the acquisition of rare microbes. Conclusion By modelling the inheritance of commensal microbes to newborns, our results suggest that, in an eco-evolutionary context, the impact of microbial inheritance is of particular importance for some specific life histories.

Maternal transmission as a microbial symbiont sieve, and the absence of lactation in male mammals

“…We examine this in Fig. 5 , extending our model to allow a fixed per-capita rate e 0 > 0 at which hosts acquire the new symbiont from an environmental source 43 . An environmental input into the host’s microbial community is potentially important, and means that the community is no longer fixed for the lifetime of the host (we do not deal with direct horizontal transmission from host to host).…”

Maternal transmission as a microbial symbiont sieve, and the absence of lactation in male mammals

“…We examine this in Fig. 5, extending our model to allow a fixed per-capita rate e 0 > 0 at which hosts acquire the new symbiont from an environmental source [40] (note we do not account for direct horizontal transmission between hosts). When e 0 is sufficiently large, horizontal transmission floods any controls generated by vertical transmission.…”

“…Rather it is the restriction of vertical transmission to just one sex, usually females, that makes the symbiont sieve work. This restriction emerges from natural selection driven by deleterious symbionts themselves, and the pattern is so ubquitous in nature [30] that it is usually taken as given in research on the theory of symbiont transmission [27,[36][37][38][39][40].…”