Optimal integration between host physiology and functions of the gut microbiome

Abstract

Host-associated microbial communities have profound impacts on animal physiological function, especially nutrition and metabolism. The hypothesis of ‘symmorphosis’, which posits that the physiological systems of animals are regulated precisely to meet, but not exceed, their imposed functional demands, has been used to understand the integration of physiological systems across levels of biological organization. Although this idea has been criticized, it is recognized as having important heuristic value, even as a null hypothesis, and may, therefore, be a useful tool in understanding how hosts evolve in response to the function of their microbiota. Here, through a hologenomic lens, we discuss how the idea of symmorphosis may be applied to host-microbe interactions. Specifically, we consider scenarios in which host physiology may have evolved to collaborate with the microbiota to perform important functions, and, on the other hand, situations in which services have been completely outsourced to the microbiota, resulting in relaxed selection on host pathways. Following this theoretical discussion, we finally suggest strategies by which these currently speculative ideas may be explicitly tested to further our understanding of host evolution in response to their associated microbial communities. This article is part of the theme issue ‘The role of the microbiome in host evolution’.

Is Gut Microbiota Dysbiosis a Predictor of Increased Susceptibility to Poor Outcome of COVID-19 Patients? An Update

“…It is now acknowledged that gut microbiota is responsible for regulating several hosts’ physiological functions [ 70 , 71 , 72 ]. Particularly, numerous studies have reported that intestinal microflora affects lung health through a bidirectional pathway designated as the “gut–lung axis” [ 73 , 74 , 75 ].…”

Antimicrobial peptides and the gut microbiome in inflammatory bowel disease

“…The appropriate maintenance of the gut microbiome is critical for health. In addition to offering competitive protection against pathogen growth, the microbiome regulates gut development[ 40 ] modulates digestion[ 41 ] and provides nutrients[ 42 ]. Thus, the microbiome must be carefully cultivated, without being permitted to proliferate excessively.…”

The role of the microbiome in host evolution

“…The complementary opinion article of McLaren & Callahan [4] argues that hosts are adapted to promote microbial taxa that confer pathogen resistance, generating what the authors aptly term 'cooperative immunity'. The interaction between host metabolism and the microbiome is considered by Fontaine & Kohl [5], who explore the value of optimality thinking, specifically symmorphosis which hypothesizes that host metabolism is structured by natural selection to match the functional demand of the association. Founded on current understanding of nutritional interactions between various animals and their microbiome, these authors predict specific testable patterns in selection pressures for microbiome-dependent regulation of host metabolic function.…”