Chapter 20
The Diazotroph as an Endophyte and How
a Diazotroph Interacts with Its Plant Host
Se-Chul Chun
Abstract The “diazotrophs” are dinitrogen-fixing (N 2 -fixing) microorganisms that
include members of the bacteria and archaea, and are functionally important
microbes that convert gaseous N 2 to ammonia (NH 3 ). There are endophytic
diazotrophic bacteria that live within plant tissues for at least part of the plants life
cycle without causing apparent disease. Diazotrophs are ubiquitous and have been
found in all species of plants studied to date. The diazotroph and plant relationships
have been much studied. Some diazotrophs may enhance host growth, nutrient
acquisition, and improve the plant’s ability to tolerate abiotic stresses such as
drought and salt. They may also induce plant resistance to insects, pathogens, and
herbivores. Recently, plant microbiome studies have attracted much attention as we
try to understand the dynamics underlying interactions of plants and microorganisms. The future is certain to bring even more genetic evidence on evolutionary
points of view regarding the diazotrophic bacteria and their hosts.
20.1 Introduction
The microorganisms are almost everywhere in our ecosystem. They are in every
form of life and every inorganic entity of its surrounding environment. The term
“diazotroph” refers to dinitrogen-fixing (N 2 -fixing) microorganisms that include
members of the bacteria and archaea, and are functionally important microbes that
convert gaseous N 2 to ammonia (NH 3 ) (Church and Böttjer 2013), playing critical
roles of geo-biochemical elemental cycling in ecosystems. Diazotrophs can be found
inside epidermal tissues of plants in which the microbes fix nitrogen from the air, or
these microbes can fix nitrogen while free living in soil. What are they doing inside
the plants? The diazotrophs reside in those environments where plant tissues offer
support for them to have a living space, and where the diazotrophs can possibly
receive nutrients such as carbohydrates. The plants benefit not only from the
S.-C. Chun (*)
Department of Environmental Health Science, Konkuk University, Seoul, Republic of Korea
e-mail: scchun@konkuk.ac.kr
© 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_20
391
The Diazotroph as an Endophyte and How
a Diazotroph Interacts with Its Plant Host
Se-Chul Chun
Abstract The “diazotrophs” are dinitrogen-fixing (N 2 -fixing) microorganisms that
include members of the bacteria and archaea, and are functionally important
microbes that convert gaseous N 2 to ammonia (NH 3 ). There are endophytic
diazotrophic bacteria that live within plant tissues for at least part of the plants life
cycle without causing apparent disease. Diazotrophs are ubiquitous and have been
found in all species of plants studied to date. The diazotroph and plant relationships
have been much studied. Some diazotrophs may enhance host growth, nutrient
acquisition, and improve the plant’s ability to tolerate abiotic stresses such as
drought and salt. They may also induce plant resistance to insects, pathogens, and
herbivores. Recently, plant microbiome studies have attracted much attention as we
try to understand the dynamics underlying interactions of plants and microorganisms. The future is certain to bring even more genetic evidence on evolutionary
points of view regarding the diazotrophic bacteria and their hosts.
20.1 Introduction
The microorganisms are almost everywhere in our ecosystem. They are in every
form of life and every inorganic entity of its surrounding environment. The term
“diazotroph” refers to dinitrogen-fixing (N 2 -fixing) microorganisms that include
members of the bacteria and archaea, and are functionally important microbes that
convert gaseous N 2 to ammonia (NH 3 ) (Church and Böttjer 2013), playing critical
roles of geo-biochemical elemental cycling in ecosystems. Diazotrophs can be found
inside epidermal tissues of plants in which the microbes fix nitrogen from the air, or
these microbes can fix nitrogen while free living in soil. What are they doing inside
the plants? The diazotrophs reside in those environments where plant tissues offer
support for them to have a living space, and where the diazotrophs can possibly
receive nutrients such as carbohydrates. The plants benefit not only from the
S.-C. Chun (*)
Department of Environmental Health Science, Konkuk University, Seoul, Republic of Korea
e-mail: scchun@konkuk.ac.kr
© 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_20
391