The Hologenome Concept - Human, Animal and Plant Microbiota (Relié)

Groundbreaking research over the last to years has given rise to the hologenome concept of evolution. This concept posits that the holohiont (host plus all of its associated microorganisms) and its hologenome (sum of the genetic information of the host and its symbiotic microorganisms), acting in concert, function as a unique biological entity and therefore as a level of selection in evolution, and so it was from the beginning.
All animals and plants harbor abundant and diverse microbiota, including viruses. Often the amount of symbiotic microorganisms and their combined genetic information far exceed that of their host. The microbiota with its microbiome, together with the host genome, can he transmitted from one generation to the next and thus propagate the unique properties of the holohiont. The microbial symbionts and the host interact in a cooperative way that affects the health of the holohiont within its environment.
Beneficial microbiota protects against pathogens, provides essential nutrients, catabolizes complex polysaccharides, renders harmful chemicals inert, and contributes to the performance of the immune system. In humans and animals, the microbiota also plays a role in behavior. The sum of these cooperative interactions characterizes the holohiont as a unique biological entity. Genetic variation in the hologenome can be brought about by changes in either the host genome or the microbial population genomes (microbiome).
Variation and evolution of holobionts include amplification of existing microbes and gaining novel microbiota in addition to horizontal gene transfer (HGT) between microbes and between microbes and hosts. Under environmental stress, the microbiome can change more rapidly and in response to more processes than the host organism alone and thus influences speciation and the evolution of holobionts. Prebiotics, probiotics, synbiotics and phage therapy are discussed as applied aspects of the hologenome concept.