The hologenome concept: we need to incorporate function

Abstract

Are we in the midst of a paradigm change in biology and have animals and plants lost their individuality, i.e., are even so-called 'typical' organisms no longer organisms in their own right? Is the study of the holobiont-host plus its symbiotic microorganisms-no longer optional, but rather an obligatory path that must be taken for a comprehensive understanding of the ecology and evolution of the individual components that make up a holobiont? Or are associated microbes merely a component of their host's environment, and the holobiont concept is just a beautiful idea that does not add much or anything to our understanding of evolution? This article explores different aspects of the concept of the holobiont. We focus on the aspect of functional integration, a central holobiont property, which is only rarely considered thoroughly. We conclude that the holobiont comes in degrees, i.e., we regard the property of being a holobiont as a continuous trait that we term holobiontness, and that holobiontness is differentiated in several dimensions. Although the holobiont represents yet another level of selection (different from classical individual or group selection because it acts on a system that is composed of multiple species), it depends on the grade of functional integration whether or not the holobiont concept helps to cast light on the various degrees of interactions between symbiotic partners.

What Is a Hologenomic Adaptation? Emergent Individuality and Inter-Identity in Multispecies Systems

“…198-233). Following the ideas of some biologists (Burke et al, 2011;Taxis et al, 2015;Catania et al, 2016;Louca et al, 2016;Doolittle and Booth, 2017;Lemanceau et al, 2017), we consider the nature of the holobiont to be such that it can support changes in its microbiome as long as the functions that the microbiome performs for the host are maintained.…”

Functional Integration and Individuality in Prokaryotic Collective Organisations

“…Several works have emphasised the importance of control and regulatory mechanisms in realising integration in different types of associations, from the development of multicellular systems (Arnellos et al 2014;Griesemer 2016 to the physiology of symbiotic relationships (Catania et al 2017;Bich 2019) 5 . Strassmann (2009, 2016), for example, have called into question the importance of spatial contiguity, the indivisibility of the parts, the development from a single lineage and the genetic uniformity among the members, to point out that it is the control of conflict and a high cooperation among the members of a society that are necessary for achieving a sufficient degree of functional integration.…”

Safety and risk assessment for the human superorganism

“…The human form is actually a composite organism, a holobiont, which includes a composite of cells and genomes (eukaryotic and microbial) (Catania et al 2016;Miller 2016). The human superorganism has trillions of microbial cells and a significant majority of microbial genes guarding the boundary between the human eukaryotic cells and the external environment (Dietert 2016a).…”