Chapter 4
Nematode-Bacterium Symbiosis
Abstract
Entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae are lethal insect
endoparasites signified by their mutualism with symbiotic bacteria in the genera Xenorhabdus and Photorhabdus, respectively. This association is an obligate mutualism in nature with each partner wanting the
other to complete its life cycle. Steinernema species form symbiosis with only one Xenorhabdus species,
whereas Photorhabdus species form symbiosis with many Heterorhabditis species. Steinernema carry their
symbiotic bacteria in a specialized vesicle called the receptacle. Heterorhabditis use their intestinal lumen to
harbor its symbiotic bacteria. These bacteria produce anti-immune proteins to help the nematode in
evading host defenses, and antimicrobials to subdue competitors.
Keywords Obligate mutualism, Gut, Intestinal lumen, Symbiosis, Nematode-bacterium complex
l
Entomopathogenic nematodes of the families Steinernematidae
and Heterorhabditidae are lethal insect endoparasites signified
by their mutualism with symbiotic bacteria in the genera Xenorhabdus and Photorhabdus, respectively.
l
This association is an obligate mutualism in nature with each
partner wanting the other to complete its life cycle.
l
There are no evidence for the isolation of Xenorhabdus and
Photorhabdus from soil assuming that these bacteria cannot
exist in the soil environment in the absence of their nematode
associates.
l
The genus Steinernema carry symbiotic bacteria in a specialized
vesicle called the receptacle, which is located in the anterior part
of the gut [67].
l
Heterorhabditis do not have such a specialized structure and use
their intestinal lumen to harbor its symbiotic bacteria in the
foregut and midgut [68].
l
The nematode infective juvenile carries between 0 and 2000 cells
of its symbiont bacterium in the anterior part of the intestine
[69, 70].
S. Sivaramakrishnan and M. Razia, Entomopathogenic Nematodes and Their Symbiotic Bacteria, Springer Protocols Handbooks,
https://doi.org/10.1007/978-1-0716-1445-7_4,
© The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature 2021
15
Nematode-Bacterium Symbiosis
Abstract
Entomopathogenic nematodes of the families Steinernematidae and Heterorhabditidae are lethal insect
endoparasites signified by their mutualism with symbiotic bacteria in the genera Xenorhabdus and Photorhabdus, respectively. This association is an obligate mutualism in nature with each partner wanting the
other to complete its life cycle. Steinernema species form symbiosis with only one Xenorhabdus species,
whereas Photorhabdus species form symbiosis with many Heterorhabditis species. Steinernema carry their
symbiotic bacteria in a specialized vesicle called the receptacle. Heterorhabditis use their intestinal lumen to
harbor its symbiotic bacteria. These bacteria produce anti-immune proteins to help the nematode in
evading host defenses, and antimicrobials to subdue competitors.
Keywords Obligate mutualism, Gut, Intestinal lumen, Symbiosis, Nematode-bacterium complex
l
Entomopathogenic nematodes of the families Steinernematidae
and Heterorhabditidae are lethal insect endoparasites signified
by their mutualism with symbiotic bacteria in the genera Xenorhabdus and Photorhabdus, respectively.
l
This association is an obligate mutualism in nature with each
partner wanting the other to complete its life cycle.
l
There are no evidence for the isolation of Xenorhabdus and
Photorhabdus from soil assuming that these bacteria cannot
exist in the soil environment in the absence of their nematode
associates.
l
The genus Steinernema carry symbiotic bacteria in a specialized
vesicle called the receptacle, which is located in the anterior part
of the gut [67].
l
Heterorhabditis do not have such a specialized structure and use
their intestinal lumen to harbor its symbiotic bacteria in the
foregut and midgut [68].
l
The nematode infective juvenile carries between 0 and 2000 cells
of its symbiont bacterium in the anterior part of the intestine
[69, 70].
S. Sivaramakrishnan and M. Razia, Entomopathogenic Nematodes and Their Symbiotic Bacteria, Springer Protocols Handbooks,
https://doi.org/10.1007/978-1-0716-1445-7_4,
© The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature 2021
15