Friend and foe: the two faces of Xenorhabdus nematophila

Herbert, E; Goodrich-Blair, Heidi

doi:10.1038/nrmicro1706

Cited by 189 publications

(199 citation statements)

References 114 publications

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“…Several studies have indicated that X. nematophila causes immunosupression at different levels 56 . The cellular response is dampened through the killing of haemocytes within 3 hours of infection, probably by the toxic effects of cytolysin, lipopolysaccharide, toxins and fimbrial subunits 56 . The humoral response can also be suppressed by repressing AMP gene expression through a mechanism that remains to be characterized 57 .…”

Section: Box 2 | Insect Immune Responsementioning

confidence: 99%

Bacterial strategies to overcome insect defences

2008

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| Recent genetic and molecular analyses have revealed how several strategies enable bacteria to persist and overcome insect immune defences. Genetic and genomic tools that can be used with Drosophila melanogaster have enabled the characterization of the pathways that are used by insects to detect bacterial invaders and combat infection. Conservation of bacterial virulence factors and insect immune repertoires indicates that there are common strategies of host invasion and pathogen eradication. Long-term interactions of bacteria with insects might ensure efficient dissemination of pathogens to other hosts, including humans. R E V I E W S302 | APRIL 2008 | voLUME 6 www.nature.com/reviews/micro

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Section: Box 2 | Insect Immune Responsementioning

confidence: 99%

Bacterial strategies to overcome insect defences

2008

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“…This method was developed to study the pathogenicity of Xenorhabdus and Photorhabdus species, which typically associate with nematode vectors as a means to gain entry into the insect. Entomopathogenic nematodes typically infect larvae via natural digestive or respiratory openings, and release their symbiotic bacterial contents into the insect hemolymph (blood) shortly thereafter 10 . The injection method described here bypasses the need for a nematode vector, thus uncoupling the effects of bacteria and nematode on the insect.…”

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confidence: 99%

Rearing and Injection of <em>Manduca sexta</em> Larvae to Assess Bacterial Virulence

Hussa

Goodrich-Blair

2012

JoVE

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Manduca sexta, commonly known as the tobacco hornworm, is considered a significant agricultural pest, feeding on solanaceous plants including tobacco and tomato. The susceptibility of M. sexta larvae to a variety of entomopathogenic bacterial species [1][2][3][4][5] , as well as the wealth of information available regarding the insect's immune system [6][7][8] , and the pending genome sequence 9 make it a good model organism for use in studying host-microbe interactions during pathogenesis. In addition, M. sexta larvae are relatively large and easy to manipulate and maintain in the laboratory relative to other susceptible insect species. Their large size also facilitates efficient tissue/hemolymph extraction for analysis of the host response to infection.The method presented here describes the direct injection of bacteria into the hemocoel (blood cavity) of M. sexta larvae. This approach can be used to analyze and compare the virulence characteristics of various bacterial species, strains, or mutants by simply monitoring the time to insect death after injection. This method was developed to study the pathogenicity of Xenorhabdus and Photorhabdus species, which typically associate with nematode vectors as a means to gain entry into the insect. Entomopathogenic nematodes typically infect larvae via natural digestive or respiratory openings, and release their symbiotic bacterial contents into the insect hemolymph (blood) shortly thereafter 10 . The injection method described here bypasses the need for a nematode vector, thus uncoupling the effects of bacteria and nematode on the insect. This method allows for accurate enumeration of infectious material (cells or protein) within the inoculum, which is not possible using other existing methods for analyzing entomopathogenesis, including nicking 11 and oral toxicity assays 12 . Also, oral toxicity assays address the virulence of secreted toxins introduced into the digestive system of larvae, whereas the direct injection method addresses the virulence of wholecell inocula.The utility of the direct injection method as described here is to analyze bacterial pathogenesis by monitoring insect mortality. However, this method can easily be expanded for use in studying the effects of infection on the M. sexta immune system. The insect responds to infection via both humoral and cellular responses. The humoral response includes recognition of bacterial-associated patterns and subsequent production of various antimicrobial peptides 7 ; the expression of genes encoding these peptides can be monitored subsequent to direct infection via RNA extraction and quantitative PCR 13 . The cellular response to infection involves nodulation, encapsulation, and phagocytosis of infectious agents by hemocytes 6 . To analyze these responses, injected insects can be dissected and visualized by microscopy 13,14 . Video LinkThe video component of this article can be found at

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“…Humoral immune responses include the production of antimicrobial peptides that can lyse bacteria (47). In the insect hemocoel, bacterial survival depends on rapidly countering immunity and killing the host, and, indeed, X. nematophila can suppress insect immunity and produces virulence factors that contribute to insect host death (26,48). Preadaptive responses that prime Xenorhabdus expression of immunosuppressive activities and toxins while still within the IJ receptacle could provide a selective advantage.…”

Section: From the Ij To The Insectmentioning

confidence: 99%

Ready or Not: Microbial Adaptive Responses in Dynamic Symbiosis Environments

Cao

Goodrich‐Blair

2017

J Bacteriol

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In mutually beneficial and pathogenic symbiotic associations, microbes must adapt to the host environment for optimal fitness. Both within an individual host and during transmission between hosts, microbes are exposed to temporal and spatial variation in environmental conditions. The phenomenon of phenotypic variation, in which different subpopulations of cells express distinctive and potentially adaptive characteristics, can contribute to microbial adaptation to a lifestyle that includes rapidly changing environments. The environments experienced by a symbiotic microbe during its life history can be erratic or predictable, and each can impact the evolution of adaptive responses. In particular, the predictability of a rhythmic or cyclical series of environments may promote the evolution of signal transduction cascades that allow preadaptive responses to environments that are likely to be encountered in the future, a phenomenon known as adaptive prediction. In this review, we summarize environmental variations known to occur in some well-studied models of symbiosis and how these may contribute to the evolution of microbial population heterogeneity and anticipatory behavior. We provide details about the symbiosis between Xenorhabdus bacteria and Steinernema nematodes as a model to investigate the concept of environmental adaptation and adaptive prediction in a microbial symbiosis.

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Friend and foe: the two faces of Xenorhabdus nematophila

Cited by 189 publications

References 114 publications

Bacterial strategies to overcome insect defences

Bacterial strategies to overcome insect defences

Rearing and Injection of <em>Manduca sexta</em> Larvae to Assess Bacterial Virulence

Ready or Not: Microbial Adaptive Responses in Dynamic Symbiosis Environments

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