About

Contemporary biology considers macroorganisms as entities inseparable from their internal and epibiotic microbial symbionts collectively referring to them as holobionts. According to the phylosymbiosis theory, the biology of a holobiont is characterized by an interdependence of the implicated parties to such degree that the evolution of the macroorganism cannot be accounted for without considering the co-evolution of its microbiomes. In fact, with regards to us humans, it is estimated that 37% of our genome is evolutionarily derived from prokaryotes. The holobiont concept includes the sum of prokaryotic and unicellular eukaryotic (microbiotic) species found at a microorganism. Microorganisms along with their sphere of influence form the microbiome. Life for macroorganisms without certain microorganisms and their functions is practically impossible, and interruptions in their ecophysiology might even lead to humanitarian crisis events.

Microorganisms develop symbiotic (e.g. commensalistic) relations with macroorganisms or may act allelopathically against them, while the initiation, the functionality and the termination of such relations is regulated by external factors and the biological traits of the implicated holobiont parties. Microorganisms are mostly important for the protection/defense, nutrition and well-being of their hosts, while their presence is sometimes necessary for the successful completement of their biological cycles.
Host-linked microbiome structure and function follows common principles among a broad range of animal and plant host organisms, while special mechanisms are developed in particular host organism cases. Those biological relations may be partly dictated by macroecological relations, whereas there are opened questions in particular cases. However, the continuous technological progress which started a couple of decades ago, and which involves multiple scientific fields, is synched with microbiome discoveries resulting in a high-speed innovation progress in that field. Finally, current microbiome study is by nature integrated, involving fields like microbiology, ecology, genetics, evolution, bioinformatics and statistics and thus demands from students in a high degree the development of critical attitude towards experimental design, analysis and presentation of associated research outcomes.

Beyond higher animal and plant hosts, recent research based on omics approaches has revealed tri-partite relations between plants-fungi-bacteria (e.g. plants-mycorrhizae-fungal endosymbiotic bacteria), or plants-fungi-insects, and also relations of viruses with other micro-/macro-organisms. Besides these we are aware of microbe-microbe interactions that were developed within the context of reciprocal rewards, or as parasitic between pray and predator. The study of the above, their governing principles, and the evolutionary relation between organisms interacting with each other, are state of the art study fields in microbial ecology and microbiology. Moreover, the study of the function of plant and animal responses under the prism of their consideration as holobionts instead of independent entities, is constantly gaining ground in associated literature, delineating the role of associated interactions in both host ecophysiology and its applied aspects like e.g. plant and animal production.