The Cytotoxic Fimbrial Structural Subunit of
            <i>Xenorhabdus nematophila</i>
            Is a Pore-Forming Toxin

Banerjee, Jyotirmoy; Singh, Jitendra; Joshi, Mohan C.; Ghosh, Shubhendu; Banerjee, Nirupama

doi:10.1128/jb.00787-06

Cited by 24 publications

(18 citation statements)

References 37 publications

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“…The ⌬cpxR1 mutant strain has altered production of several exoenzymes with known or suspected roles in X. nematophila virulence for insects and bioconversion of the insect carcass, including increased hemolysin (8,74) and protease (9) secreted activities, as well as increased transcripts of genes encoding these activities (Table 3). Of particular note is the finding that the ⌬cpxR1 mutant exhibited an increase in expression of mrxA (Table 3) encoding a pilin subunit (32) with pore-forming toxin activity (3). MrxA is present in X. nematophila outer membrane vesicles (OMVs) that are toxic to insects.…”

Section: Role Of X Nematophila Cpxr In Host Interactionsmentioning

confidence: 99%

CpxRA Regulates Mutualism and Pathogenesis in Xenorhabdus nematophila

Herbert

Cowles

Goodrich-Blair

2007

Appl Environ Microbiol

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The CpxRA signal transduction system, which in Escherichia coli regulates surface structure assembly and envelope maintenance, is involved in the pathogenic and mutualistic interactions of the entomopathogenic bacterium Xenorhabdus nematophila. When ⌬cpxR1 cells were injected into Manduca sexta insects, the time required to kill 50% of the insects was twofold longer than the time observed for wild-type cells and the ⌬cpxR1 cells ultimately killed 16% fewer insects than wild-type cells killed. During mutualistic colonization of Steinernema carpocapsae nematodes, the ⌬cpxR1 mutant achieved colonization levels that were only 38% of the wild-type levels. ⌬cpxR1 cells exhibited an extended lag phase when they were grown in liquid LB or hemolymph, formed irregular colonies on solid medium, and had a filamentous cell morphology. A mutant with a cpxRp-lacZ fusion had peaks of expression in the log and stationary phases that were conversely influenced by CpxR; the ⌬cpxR1 mutant produced 130 and 17% of the wild-type ␤-galactosidase activity in the log and stationary phases, respectively. CpxR positively influences motility and secreted lipase activity, as well as transcription of genes necessary for mutualistic colonization of nematodes. CpxR negatively influences the production of secreted hemolysin, protease, and antibiotic activities, as well as the expression of mrxA, encoding the pilin subunit. Thus, X. nematophila CpxRA controls expression of envelope-localized and secreted products, and its activity is necessary for both mutualistic and pathogenic functions.

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Section: Role Of X Nematophila Cpxr In Host Interactionsmentioning

confidence: 99%

CpxRA Regulates Mutualism and Pathogenesis in Xenorhabdus nematophila

Herbert

Cowles

Goodrich-Blair

2007

Appl Environ Microbiol

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“…Oral administration of purified Pit protein results in an inhibition of growth with the larvae of Spodoptera litura and H. armigera, but did not kill the insects; however the injectable activity of the toxin was much greater. In Xenorhabdus the type 1 fimbrial protein, MrxA, recently implicated in nematode colonisation was previously identified as a putative pore-forming toxin which targets hemocytes thus preventing phagocytosis [59,60]. The same group also identified an insecticidal pilin subunit associated with outer membrane vesicles (OMVs) which appear to bleb from X. nematophilus [123,124].…”

Section: A Host Of Other Insecticidal Toxinsmentioning

confidence: 99%

“…Three phenethylamide compounds, purified from the culture broth of X. nematophila have demonstrable cytotoxicity towards hemocytes and may induce apoptosis by activating cytochrome c-dependent caspase-3 [57,58]. In addition a type 1 fimbrial protein, MrxA, has been shown to be toxic to cultured hemocytes and is able to form pores in cell membranes [59,60]. Bacteria unable to produce this protein showed reduced hemocyte toxicity in the larval hemocoel during early stage of infection and delayed larval mortality [60].…”

Section: Evasion Of the Cellular Responsementioning

confidence: 99%

Overview of the Basic Biology of Bacillus thuringiensis with Emphasis on Genetic Engineering of Bacterial Larvicides for Mosquito Control

Federici¹

2013

TOTNJ

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Insect pathogens are an excellent source of novel insecticidal agents with proven toxicity. In particular, bacteria from the genera Photorhabdus and Xenorhabdus are proving to be a genomic goldmine, encoding a multitude of insecticidal toxins. Some are highly specific in their target species, whilst others are more generalist, but all are of potential use in crop protection against insect pests. These astounding bacterial species are also turning out to be equipped to produce a vast range of anti-microbial compounds which could be of use to medical science. This review will cover the current knowledge of the lifecycles of the two genera and the potential role of the toxins in their biology, before a more in depth exploration of some of the best studied toxins and their potential use in agriculture.

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“…MrxA was shown to be associated with outer membrane vesicles (OMVs) that exhibited oral toxicity toward the lepidopteran Helicoverpa armigera (25). Purified MrxA exhibited cytotoxic properties and recombinant MrxA displayed oral toxicity and functioned as a pore-forming toxin on targeted insect hemocytes (5,26).…”

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confidence: 99%

Role of Mrx Fimbriae of Xenorhabdus nematophila in Competitive Colonization of the Nematode Host

Snyder

Owen

et al. 2011

Appl Environ Microbiol

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Xenorhabdus nematophila engages in mutualistic associations with the infective juvenile (IJ) stage of specific entomopathogenic nematodes. Mannose-resistant (Mrx) chaperone-usher-type fimbriae are produced when the bacteria are grown on nutrient broth agar (NB agar). The role of Mrx fimbriae in the colonization of the nematode host has remained unresolved. We show that X. nematophila grown on LB agar produced flagella rather than fimbriae. IJs propagated on X. nematophila grown on LB agar were colonized to the same extent as those propagated on NB agar. Further, progeny IJs were normally colonized by mrx mutant strains that lacked fimbriae both when bacteria were grown on NB agar and when coinjected into the insect host with aposymbiotic nematodes. The mrx strains were not competitively defective for colonization when grown in the presence of wild-type cells on NB agar. In addition, a phenotypic variant strain that lacked fimbriae colonized as well as the wild-type strain. In contrast, the mrx strains displayed a competitive colonization defect in vivo. IJ progeny obtained from insects injected with comixtures of nematodes carrying either the wild-type or the mrx strain were colonized almost exclusively with the wild-type strain. Likewise, when insects were coinjected with aposymbiotic IJs together with a comixture of the wild-type and mrx strains, the resulting IJ progeny were predominantly colonized with the wild-type strain. These results revealed that Mrx fimbriae confer a competitive advantage during colonization in vivo and provide new insights into the role of chaperone-usher fimbriae in the life cycle of X. nematophila.Xenorhabdus nematophila is a host-adapted enteric bacterium that engages in mutualistic associations with specific entomopathogenic nematodes and is also pathogenic toward diverse insects (1,8,18,46). X. nematophila colonizes a specialized region of the anterior intestine (receptacle) of the infective juvenile (IJ) stage of the nematode (8, 41). The IJ enters the intestine of diverse insect hosts and subsequently invades the insect body cavity and releases X. nematophila into the insect blood (hemolymph). During early stages of infection, the bacteria adhere to connective tissue and musculature surrounding the insect midgut (36). X. nematophila proliferates in the hemolymph, where it inactivates the host immune response and produces an array of toxins and exoenzymes that are involved in killing the host. The bacteria also secrete antimicrobial compounds that suppress microbial competitors (16,22,33,35,48). Proliferation of Xenorhabdus in the insect establishes a nutrient base for nematode growth and reproduction. After several cycles of reproduction the nematodes develop into IJ progeny that are colonized by one or a few X. nematophila cells that multiply in the nematode receptacle, which is formed by 2 specialized intestinal cells (29,30,41). Almost all IJ progeny that emerge from the insect cadaver contain X. nematophila, though the level of colonization can vary considerably between ind...

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The Cytotoxic Fimbrial Structural Subunit of Xenorhabdus nematophila Is a Pore-Forming Toxin

Cited by 24 publications

References 37 publications

CpxRA Regulates Mutualism and Pathogenesis in Xenorhabdus nematophila

CpxRA Regulates Mutualism and Pathogenesis in Xenorhabdus nematophila

Overview of the Basic Biology of Bacillus thuringiensis with Emphasis on Genetic Engineering of Bacterial Larvicides for Mosquito Control

Role of Mrx Fimbriae of Xenorhabdus nematophila in Competitive Colonization of the Nematode Host

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