Xiong Xiyan, Loo Sara L, Tanaka Mark M
School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
Evolution and Ecology Research Centre, University of New South Wales, Sydney, NSW 2052, Australia.
Evol Hum Sci. 2022 Sep 2;4:e41. doi: 10.1017/ehs.2022.38. eCollection 2022.
Humans harbour diverse microbial communities, and this interaction has fitness consequences for hosts and symbionts. Understanding the mechanisms that preserve host-symbiont association is an important step in studying co-evolution between humans and their mutualist microbial partners. This association is promoted by vertical transmission, which is known to be imperfect. It is unclear whether host-microbial associations can generally be maintained despite 'leaky' vertical transmission. Cultural practices of the host are expected to be important in bacterial transmission as they influence the host's interaction with other individuals and with the environment. There is a need to understand whether and how cultural practices affect host-microbial associations. Here, we develop a mathematical model to identify the conditions under which the mutualist can persist in a population where vertical transmission is imperfect. We show with this model that several factors compensate for imperfect vertical transmission, namely, a selective advantage to the host conferred by the mutualist, horizontal transmission of the mutualist through an environmental reservoir and transmission of a cultural practice that promotes microbial transmission. By making the host-microbe association more likely to persist in the face of leaky vertical transmission, these factors strengthen the association which in turn enables host-mutualist co-evolution.
人类体内存在着多样的微生物群落，这种相互作用对宿主和共生体的健康状况都会产生影响。了解维持宿主 - 共生体关联的机制是研究人类与其互利微生物伙伴共同进化的重要一步。垂直传播促进了这种关联，不过已知其并不完美。尚不清楚尽管垂直传播存在“漏洞”，宿主 - 微生物关联是否总体上仍能维持。宿主的文化习俗在细菌传播中预计起着重要作用，因为它们会影响宿主与其他个体以及与环境的相互作用。有必要了解文化习俗是否以及如何影响宿主 - 微生物关联。在此，我们构建了一个数学模型，以确定在垂直传播不完美的种群中互利共生体能够持续存在的条件。我们用这个模型表明，有几个因素可以弥补不完美的垂直传播，即互利共生体赋予宿主的选择优势、互利共生体通过环境库进行的水平传播以及促进微生物传播的文化习俗的传播。通过使宿主 - 微生物关联在垂直传播存在漏洞的情况下更有可能持续存在，这些因素加强了这种关联，进而推动宿主 - 互利共生体的共同进化。
