Symbiosis as the way of eukaryotic life: The dependent co-origination of the body.
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Date
2014-04
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Abstract
Molecular analyses of symbiotic relationships are challenging our biological definitions of individuality and
supplanting them with a new notion of normal part–whole relationships. This new notion is that of a ‘holobiont’, a
consortium of organisms that becomes a functionally integrated ‘whole’. This holobiont includes the zoological
organism (the ‘animal’) as well as its persistent microbial symbionts. This new individuality is seen on anatomical and
physiological levels, where a diversity of symbionts form a new ‘organ system’ within the zoological organism and
become integrated into its metabolism and development. Moreover, as in normal development, there are reciprocal
interactions between the ‘host’ organism and its symbionts that alter gene expression in both sets of cells. The immune
system, instead of being seen as functioning solely to keep microbes out of the body, is also found to develop, in part,
in dialogue with symbionts. Moreover, the immune system is actively involved in the colonization of the zoological
organism, functioning as a mechanism for integrating microbes into the animal-cell community. Symbionts have also
been found to constitute a second mode of genetic inheritance, providing selectable genetic variation for natural
selection. We develop, grow and evolve as multi-genomic consortia/teams/ecosystems.
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Evolution, holobiont, individuality, symbionts, symbiosis
Citation
Gilbert Scott F. Symbiosis as the way of eukaryotic life: The dependent co-origination of the body. Journal of Biosciences. 2014 Apr; 39 (2): 201-209.