Abstract

Over the last three decades, studies in microbiology have exposed a world of diverse and dynamic interactions. Through metagenomic sequencing, complex bacterial communities became visible and proved important for many biological phenomena. As a result of discovering the connection between microorganisms and organisms’ survival, the notion of the holobiont has become prominent and has been suggested as a biological individual. The view of the holobiont as an individual, commonly known as the Hologenome Theory, focuses on the interactions and relations between the host and its symbionts in the host’s development and evolution. Today, the holobiont is at the heart of the debate on the nature of the biological individual, a debate which is connected to the same question about the nature of the individual organism.