The Microbiome and Bone

Abstract

Eukaryotic organisms evolved in environments containing bacteria and archea. Findings over the past decade have demonstrated that the physiology of vertebrates is greatly influenced by the microbes that reside in the body– a population of organisms known as the microbiome. The composition of the gut microbiome has co‐evolved with vertebrates leading, to species‐specific populations linked to vertebrate phylogeny. Bones are among the most visually compelling parts of vertebrate anatomy and are integral to the interpretation of phylogeny in the fossil record. A connection between the microbiome and bone morphology therefore has the potential to have substantial influence on the interpretation of the fossil record. Here I provide an introduction to the microbiome, including the state of the art in the field and current concepts regarding how the gut microbiome may influence distant organs such as bone. The effects of the gut microbiome on bone morphology were established in the first animals studies using antibiotics in the 1930s but only recently have studies attempted to explain the connection between the gut microbiome and bone. Laboratory studies over the past few years have described profound effects of changes in the composition of the gut microbiome on cortical and cancellous bone morphology. These studies suggest that the gut microbiome can regulate whole bone length and appositional bone growth leading to changes in cortical bone morphology. Additionally, recent studies in mice suggest that, in some cases, a bone phenotype can be transferred from one mouse strain to another by transfer of the gut microbiota alone. Together with recent studies suggesting co‐adaptation of commensal microbes and their hosts, these studies suggest regulation of bone morphology by the microbiome.