Effects of Growth Conditions on the Forms of Xenorhabdus nematophila: A Symbiotic Bacterium of the Entomopathogenic Steinernema carpocapsae

Abstract Steinernema carpocapsae is an entomopathogenic nematode (EPN) used in biological control of agricultural pest insects. It enters the hemocoel of its host via the intestinal tract and releases its symbiotic bacterium Xenorhabdus nematophila. In order to improve our knowledge about the physiological responses of its different hosts, we examined the transcriptional responses to EPN infestation of the fat body, the hemocytes and the midgut in the lepidopteran pest Spodoptera frugiperda. The tissues poorly respond to the infestation at an early time post-infestation of 8 h with only 5 genes differentially expressed in the fat body of the caterpillars. Strong transcriptional responses are observed at a later time point of 15 h post-infestation in all three tissues. Few genes are differentially expressed in the midgut but tissue-specific panels of induced metalloprotease inhibitors, immune receptors and antimicrobial peptides together with several uncharacterized genes are up-regulated in the fat body and the hemocytes. Among the most up-regulated genes, we identified new potential immune effectors, unique to Lepidoptera, which show homology with bacterial genes of unknown function. Altogether, these results pave the way for further functional studies of the responsive genes’ involvement in the interaction with the EPN.

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Studying the Symbiotic Bacterium Xenorhabdus nematophila in Individual, Living Steinernema carpocapsae Nematodes Using Microfluidic Systems

mSphere ◽

10.1128/msphere.00530-17 ◽

2018 ◽

Vol 3 (1) ◽

Cited By ~ 6

Author(s):

Matthew D. Stilwell ◽

Mengyi Cao ◽

Heidi Goodrich-Blair ◽

Douglas B. Weibel

Keyword(s):

Entomopathogenic Nematode ◽

Experimental System ◽

Symbiotic Bacterium ◽

Lessons Learned ◽

Steinernema Carpocapsae ◽

Infective Juvenile ◽

Xenorhabdus Nematophila ◽

Bacterial Populations ◽

Individual Host ◽

Host Microbe Interactions

This paper describes an experimental system for directly investigating population dynamics of a symbiotic bacterium,Xenorhabdus nematophila, in its host—the infective stage of the entomopathogenic nematodeSteinernema carpocapsae. Tracking individual and groups of bacteria in individual host nematodes over days and weeks yielded insight into dynamic growth and topology changes of symbiotic bacterial populations within infective juvenile nematodes. Our approach for studying symbioses between bacteria and nematodes provides a system to investigate long-term host-microbe interactions in individual nematodes and extrapolate the lessons learned to other bacterium-animal interactions.

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Histological observations by light and scanning electron microscopy of the Japanese pine sawyer, Monochamus alternatus, infected with the entomopathogenic nematode, Steinernema carpocapsae

Nematology ◽

10.1163/15685411-00003073 ◽

2017 ◽

Vol 19 (5) ◽

pp. 597-603

Author(s):

Yasuharu Mamiya ◽

Tugio Shoji

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Entomopathogenic Nematode ◽

Symbiotic Bacterium ◽

Steinernema Carpocapsae ◽

Xenorhabdus Nematophila ◽

Monochamus Alternatus ◽

Japanese Pine Sawyer ◽

Insect Reproduction ◽

Scanning Electron

Light (LM) and scanning electron microscopy (SEM) were used to study infection of adults and larvae of the Japanese pine sawyer,Monochamus alternatus, by infective juveniles (IJ) ofSteinernema carpocapsae(Mexican strain). The IJ entered the alimentary canal of both larvae and adults ofM. alternatusviathe anus. Entry through spiracles was not observed. Both larvae and adult died within 48 h after infection. SEM revealed the changes in the distribution and reproduction of the symbiotic bacterium,Xenorhabdus nematophila, in the insect body over time. The observations were consistent with the hypothesis that septicaemia was the main cause of insect death. Bacteria grew vigorously and were distributed widely in the insect body as soon as the IJ invaded the insect. Reproduction of the nematode within the insect followed the reproduction of the bacterium throughout the insect body.

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Xenorhabdus nematophila Requires an Intact iscRSUA-hscBA-fdx Operon To Colonize Steinernema carpocapsae Nematodes

Journal of Bacteriology ◽

10.1128/jb.185.12.3678-3682.2003 ◽

2003 ◽

Vol 185 (12) ◽

pp. 3678-3682 ◽

Cited By ~ 13

Author(s):

Eric C. Martens ◽

Joseph Gawronski-Salerno ◽

Danielle L. Vokal ◽

Molly C. Pellitteri ◽

Megan L. Menard ◽

...

Keyword(s):

Steinernema Carpocapsae ◽

Xenorhabdus Nematophila ◽

Coordinated Expression

ABSTRACT An insertion between iscA and hscB of the Xenorhabdus nematophila iscRSUA-hscBA-fdx locus, predicted to encode Fe-S assembly machinery, prevented colonization of Steinernema carpocapsae nematodes. The insertion disrupted cotranscription of iscA and hscB, but did not reduce hscBA expression, suggesting that X. nematophila requires coordinated expression of the isc-hsc-fdx locus for colonization.

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Partner-specific induction of Spodoptera frugiperda immune genes in response to the entomopathogenic nematobacterial complex Steinernema carpocapsae-Xenorhabdus nematophila

Developmental & Comparative Immunology ◽

10.1016/j.dci.2020.103676 ◽

2020 ◽

Vol 108 ◽

pp. 103676

Author(s):

Louise Huot ◽

Audrey Bigourdan ◽

Sylvie Pagès ◽

Jean-Claude Ogier ◽

Pierre-Alain Girard ◽

...

Keyword(s):

Spodoptera Frugiperda ◽

Steinernema Carpocapsae ◽

Xenorhabdus Nematophila ◽

Immune Genes ◽

Specific Induction

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The Xenorhabdus nematophila nilABC Genes Confer the Ability of Xenorhabdus spp. To Colonize Steinernema carpocapsae Nematodes

Journal of Bacteriology ◽

10.1128/jb.00123-08 ◽

2008 ◽

Vol 190 (12) ◽

pp. 4121-4128 ◽

Cited By ~ 36

Author(s):

Charles E. Cowles ◽

Heidi Goodrich-Blair

Keyword(s):

Sequence Analysis ◽

Host Range ◽

Range Expansion ◽

Genetic Locus ◽

Host Tissue ◽

Steinernema Carpocapsae ◽

Genetic Element ◽

Xenorhabdus Nematophila ◽

Host Range Expansion ◽

Species Specific

ABSTRACT Members of the Steinernema genus of nematodes are colonized mutualistically by members of the Xenorhabdus genus of bacteria. In nature, Steinernema carpocapsae nematodes are always found in association with Xenorhabdus nematophila bacteria. Thus, this interaction, like many microbe-host associations, appears to be species specific. X. nematophila requires the nilA, nilB, and nilC genes to colonize S. carpocapsae. In this work, we showed that of all the Xenorhabdus species examined, only X. nematophila has the nilA, nilB, and nilC genes. By exposing S. carpocapsae to other Xenorhabdus spp., we established that only X. nematophila is able to colonize S. carpocapsae; therefore, the S. carpocapsae-X. nematophila interaction is species specific. Further, we showed that introduction of the nilA, nilB, and nilC genes into other Xenorhabdus species enables them to colonize the same S. carpocapsae host tissue that is normally colonized by X. nematophila. Finally, sequence analysis supported the idea that the nil genes were horizontally acquired. Our findings indicate that a single genetic locus determines host specificity in this bacteria-animal mutualism and that host range expansion can occur through the acquisition of a small genetic element.

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Mechanisms of specificity of association between the nematode Steinernema scapterisci and its symbiotic bacterium

Parasitology ◽

10.1017/s0031182096008669 ◽

1997 ◽

Vol 114 (5) ◽

pp. 483-488 ◽

Cited By ~ 17

Author(s):

P. S. GREWAL ◽

M. MATSUURA ◽

V. CONVERSE

Keyword(s):

Galleria Mellonella ◽

Entomopathogenic Nematode ◽

Symbiotic Bacterium ◽

Bacterial Symbiont ◽

Steinernema Carpocapsae ◽

Infective Juvenile ◽

Symbiotic Bacteria ◽

Bacterial Symbionts ◽

First Report ◽

Successful Isolation

We suggest a new mechanism for the maintenance of specificity of the association between the entomopathogenic nematode Steinernema scapterisci and its symbiotic bacteria. We evaluated the development and reproduction of infective and non-infective juvenile S. scapterisci in monoxenic combinations with its symbiotic bacteria, Xenorhabdus sp. ‘S’ and with the bacterial symbiont of Steinernema carpocapsae and Steinernema riobravis. Although development of non-infective stages occurred on all Xenorhabdus spp., the development of infective juveniles to the 4th stage (‘dauer’ recovery) was significantly delayed and reduced with X. nematophilus and Xenorhabdus sp. ‘R’, the bacterial symbionts of S. carpocapsae and S. riobravis, respectively. ‘Dauer’ recovery improved significantly when the cultures of X. nematophilus and Xenorhabdus sp. ‘R’ were supplemented with cell-free filtrates from Xenorhabdus sp. ‘S’. The infective juvenile S. scapterisci produced in all 3 cultures were virulent to Galleria mellonella larvae, confirming successful retention of Xenorhabdus from other steinernematids in their intestine. In fact, S. scapterisci infective juveniles containing X. nematophilus or Xenorhabdus sp. ‘R’ were more virulent to G. mellonella than those containing their natural symbiont, Xenorhabdus sp. ‘S’. We believe that this is the first demonstration of the symbiont-specific exit of infective juveniles from the ‘dauer’ phase which represents the finest level of specificity of bacteria–nematode association. This is also the first report of successful isolation of the natural symbiont of S. scapterisci.

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Early Colonization Events in the Mutualistic Association between Steinernema carpocapsae Nematodes and Xenorhabdus nematophila Bacteria

Journal of Bacteriology ◽

10.1128/jb.185.10.3147-3154.2003 ◽

2003 ◽

Vol 185 (10) ◽

pp. 3147-3154 ◽

Cited By ~ 109

Author(s):

Eric C. Martens ◽

Kurt Heungens ◽

Heidi Goodrich-Blair

Keyword(s):

Fluorescent Protein ◽

Ex Vivo ◽

Entomopathogenic Nematode ◽

Steinernema Carpocapsae ◽

Infective Juvenile ◽

Bacterial Cells ◽

Biological Interactions ◽

Xenorhabdus Nematophila ◽

Molecular Events ◽

Final Population

ABSTRACT The bacterium Xenorhabdus nematophila is a mutualist of the entomopathogenic nematode Steinernema carpocapsae. During its life cycle, the bacterium exists both separately from the nematode and as an intestinal resident of a nonfeeding nematode form, the infective juvenile (IJ). The progression of X. nematophila from an ex vivo existence to a specific and persistent colonization of IJs is a model to understand the mechanisms mediating the initiation and maintenance of benign host-microbe interactions. To help characterize this process, we constructed an X. nematophila strain that constitutively expresses green fluorescent protein, which allowed its presence to be monitored within IJs. Using this strain, we showed that few bacterial cells initiate colonization of an individual IJ and that these grow inside the lumen of the IJ intestine in a reproducible polyphasic pattern during colonization. In accordance with these two observations, we demonstrated that the final population of bacteria in a nematode is of predominantly monoclonal origin, suggesting that only one or two bacterial clones initiate or persist during colonization of an individual nematode. These data suggest that X. nematophila initiates IJ colonization by competing for limited colonization sites or resources within the nematode intestine. This report represents the first description of the biological interactions occurring between X. nematophila and S. carpocapsae during the early stages of the colonization process, provides insights into the physiology of X. nematophila in its host niche, and will facilitate interpretation of future data regarding the molecular events mediating this process.

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