Xenorhabdus nematophilus

Introduction

File:KhandelwalXn.jpg

A Thin section of an X. nematophilus cell, showing outer membrane blebs on the surface of the cell and in the surrounding area. B Negatively stained outer membrane vesicles in X. nematophilus cells showing electron-dense substances enclosed within.

Xenorhabdus nematophilus is a bacterium that exists in a symbiotic relationship with nematodes. Steinernema is the genus of nematodes that the bacterium resides in. The interaction is specific to each species. They are found ubiquitously in soil environments. Their ecological significance is particularly apparent in agriculture, as a form of biological control of pest insect species. The biological processes of the bacterium are matched by the needs of the nematode and vice versa. Together this mutualistic relationship results in the predation of insect species, such as those in the order Lepidoptera.

==Xenorhabdus nematophilus== Phases link to microbial processes. Entomopathogenic vs pathogenic

Xenorhabdus nematophilus is a bacterium

Biological interaction

The life cycle of the nematode is completed in a few days, and it results in thousands of new infective juveniles looking for hosts. Source: http://www.biocontrol.entomology.cornell.edu/pathogens/nematodes.html

The interaction between Xenorhabdus nematophilus and Steinernema carpocapsae is a specific mutualism.

Why S. carpocapsae needs X. nematophilus 1

The nematode is not a free living organism and requires a host for its life cycle to be completed. Only the infective juvenile stage of S. carpocapsae is able to move through the environment in order to find a new host.

Limited competition 1a

In the initial stages of infection of the insect host, X. nematophilus inhibits the growth of various fungal and bacterial competitors. The metabolites exuded by the bacterium are known to have antifungal, nematicidal, or insecticidal effects.

Effectively kills the host 1b

The Steinernema carpocapsae species of nematode is only free living during its juvenile stage. It is at this time that they are infective and seek out hosts. The nematode needs the bacterium to effectively kill the insect host and complete its life cycle. The bacteria provide nutrients for the nematode development.

Why the X. nematophilus needs S. carpocapsae 2

The bacterium X. nematophilus is not found in the soil environment. It cannot survive in water or soil for long by itself; it needs the nematode (Photorhabdus has the same characteristic).

Finds Host 2a

finds, enters/penetrates dispersal

Effectively kills the host 2b

The nematode allows the bacterium to enter the homocoel of the insect. DEFINE homocoel.

Interactions with other species 5

potato

negative/positive?. outcome?

fungi

X. nematophilus has antagonistic interactions with entomopathogenic fungi.

<<Provide details of the symbiosis or biological interaction. Is this a specific or general interaction? How do these interactions influence the host or other microbial populations, and their activities? How do these interactions influence other organisms (positive or negative influences)? What is the outcome of this interaction? Are there ecological consequences? Describe biological interactions using as many sections/subsections as you require. Look at other topics available in MicrobeWiki. Create links where relevant.>>

Niche

Xenorhabdus nematophilus is ubiquitous across all habitat types. Since it has been shown that Steinernematid (and Heterorhabditid) nematodes are exclusive to soil environments, and they have been isolated from every continent, excluding Antarctica. Entomopathogenic nematodes exist in a diverse range of soil habitats including farmland, forests, beaches, and deserts. A survey of entomopathogenic nematodes had confirmation of the nematodes in 2-25% of the sites sampled.

Key Microorganisms, Microbial Communities

A Entomopathogenic nematode, infective juevenile stage. B Infected Galleria mellonella (wax moth) larva with nematodes emerging. Source: http://www.biocontrol.entomology.cornell.edu/pathogens/nematodes.html

What specific kinds of microbes are typically involved in this interaction? Or associated with important processes? Describe key groups (genera, species) of microbes that we find in this environment, and any special adaptations they may have evolved to survive in this environment. List examples of specific microbes that represent key groups or are associated with important processes found in this environment. Add sections/subsections as needed. Look at other microbe listings in MicrobeWiki. Are some of the groups of microbes from your environment already described? Create links to other MicrobeWiki pages where possible.

Phases of X. nematophilus 1

X. nematophilus is believed to have phase I and phase II forms.

Microbial processes

What microbial processes are important for this microbial interaction? Does this microbial interaction have some ecosystem-level effects? Does this interaction affect the environment in any way? Describe critical microbial processes or activities that are important in this interaction, adding sections/subsections as needed. Look at other topics in MicrobeWiki. Are some of these processes already described? Create links where relevant.

Current Research

Biological Control

Agriculture

What factors allow for the bacteria to recognize environment?

The bacteria must have some mechanism by which to recognize whether it is in it’s host environment and regulate gene expression accordingly.

References

Shapiro-IIan, D. I.and Gaugler, R. "Rhabditida: Steinernematidae & Heterorhabditidae Biological Control, Nematodes". Cornell University, College of Agriculture and Life Sciences, Department of Entomology.

[Sample reference] Takai, K., Sugai, A., Itoh, T., and Horikoshi, K. "Palaeococcus ferrophilus gen. nov., sp. nov., a barophilic, hyperthermophilic archaeon from a deep-sea hydrothermal vent chimney". International Journal of Systematic and Evolutionary Microbiology. 2000. Volume 50. p. 489-500.

Edited by Chloe M. Mattia, a student of Angela Kent at the University of Illinois at Urbana-Champaign.