Chapter 27
The Importance of Being Symbiont
and the Role of Symbiosis as a Driving Force
in Evolution
Francisco Carrapiço
Abstract We live in a symbiotic world where many living forms, from the simplest
to the most complex ones, have associations with microorganisms. Thus, symbiosis
plays a very important role in the origin, organization, and evolution of life. Given
their role in the association, symbionts are among the key actors in this interplay.
Traditionally, the symbiont is seen as a supporting actor, with a secondary role in the
play, whereas the host is understood as having the leading role. However, bacteria
and, more recently, viruses have gradually come to be seen as important elements of
these symbiotic relationships or consortia, and as one of the key factors in the
evolution and organization of the web of life, as well as its health and disease. The
gut microbiome, namely in humans, is another important case study to understand
the importance of symbionts. Misunderstood and diabolized for a long time, the
human gastrointestinal microbiome represents a challenge and an opportunity to
understand in a holistic way how the human body works and the effects that it has on
our health. This could be the beginning of a new paradigm in science, namely in
biology and medicine, that remains almost unexplored and that challenges the
traditional concept of organism.
27.1 Introduction
Evolution is traditionally considered a gradual process essentially consisting of
natural selection, conducted on minimal phenotypical variations that are the result
of mutations and genetic recombinations to form new species (Darwin 1859;
Dawkins 1976; Huxley 1942; Mayr 1942, 1982, 2001; Wilson 1975). This is the
case even in models of evolutionary change, such as the punctuated equilibria, which
can be considered as a rupture with the neo-Darwinian tenets (Eldredge and Gould
F. Carrapiço (*)
Centro de Ecologia, Evolução e Alterações Ambientais and Centro de Filosofia das Ciências,
Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Lisbon,
Portugal
e-mail: fcarrapico@fc.ul.pt
© Springer Nature Switzerland AG 2021
C. J. Hurst (ed.), Microbes: The Foundation Stone of the Biosphere, Advances in
Environmental Microbiology 8, https://doi.org/10.1007/978-3-030-63512-1_27
595
The Importance of Being Symbiont
and the Role of Symbiosis as a Driving Force
in Evolution
Francisco Carrapiço
Abstract We live in a symbiotic world where many living forms, from the simplest
to the most complex ones, have associations with microorganisms. Thus, symbiosis
plays a very important role in the origin, organization, and evolution of life. Given
their role in the association, symbionts are among the key actors in this interplay.
Traditionally, the symbiont is seen as a supporting actor, with a secondary role in the
play, whereas the host is understood as having the leading role. However, bacteria
and, more recently, viruses have gradually come to be seen as important elements of
these symbiotic relationships or consortia, and as one of the key factors in the
evolution and organization of the web of life, as well as its health and disease. The
gut microbiome, namely in humans, is another important case study to understand
the importance of symbionts. Misunderstood and diabolized for a long time, the
human gastrointestinal microbiome represents a challenge and an opportunity to
understand in a holistic way how the human body works and the effects that it has on
our health. This could be the beginning of a new paradigm in science, namely in
biology and medicine, that remains almost unexplored and that challenges the
traditional concept of organism.
27.1 Introduction
Evolution is traditionally considered a gradual process essentially consisting of
natural selection, conducted on minimal phenotypical variations that are the result
of mutations and genetic recombinations to form new species (Darwin 1859;
Dawkins 1976; Huxley 1942; Mayr 1942, 1982, 2001; Wilson 1975). This is the
case even in models of evolutionary change, such as the punctuated equilibria, which
can be considered as a rupture with the neo-Darwinian tenets (Eldredge and Gould
F. Carrapiço (*)
Centro de Ecologia, Evolução e Alterações Ambientais and Centro de Filosofia das Ciências,
Departamento de Biologia Vegetal, Faculdade de Ciências, Universidade de Lisboa, Lisbon,
Portugal
e-mail: fcarrapico@fc.ul.pt
© Springer Nature Switzerland AG 2021
C. J. Hurst (ed.), Microbes: The Foundation Stone of the Biosphere, Advances in
Environmental Microbiology 8, https://doi.org/10.1007/978-3-030-63512-1_27
595