In plants, the colonizing process can be initiated below ground in the root zone, around the germinating seed, the spermosphere, or originate from the above ground parts, the phyllosphere and the flower zone or anthosphere.
Within the hologenome theory, the holobiont has not only become the principal unit of natural selection but also the result of other step of integration that it is also observed at the cell (symbiogenesis, endosymbiosis) and genomic levels.
Targeted amplicon sequencing relies on having some expectations about the composition of the community that is being studied.
Co-evolution (also called "hologenome theory") proposes that an object of natural selection is not the individual organism, but the organism together with its associated organisms, including its microbial communities. The hologenome theory originated in studies on coral reefs.
Coral reefs are the largest structures created by living organisms, and contain abundant and highly complex microbial communities.
The symbiotic relationship between a host and its microbiota shapes the immune system of mammalians, In many animals, the immune system and microbiota engage in "cross-talk", exchanging chemical signals.
This allows the immune system to recognize the types of bacteria that are harmful to the host and combat them, while allowing the helpful bacteria to carry out their functions; in turn, the microbiota influence immune reactivity and targeting.
It should also evolve in such a way that it is conserved enough that primers can target genes from a wide range of organisms while evolving quickly enough to allow for finer resolution at the taxonomic level.
A common marker for human microbiome studies is the gene for bacterial 16S r RNA (i.e.
Extrapolating this hypothesis to other organisms, including higher plants and animals, led to the proposal of the "hologenome theory of evolution". shiloi was misidentified as the causative agent of coral bleaching, and that its presence in bleached O.
patagonica was simply that of opportunistic colonization.
Over the past several decades, major declines in coral populations have occurred.