Interaction of avirulent transpositional mutants of Xenorhabdus nematophilus ATCC 19061 (Enterobacteriaceae) with the antibacterial systems of non-immune Galleria mellonella (Insecta) larvae.

Dunphy, Gary B.; Hurlbert, Ronald E.

doi:10.2323/jgam.41.409

Cited by 11 publications

(19 citation statements)

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“…X. nematophilus 19061 and avirulent mutants AV1, GF, and G (transpositional mutants of strain 19061 [7]), V. harveyi B392 and the autoinducer mutant D1 (4), and Escherichia coli were all grown at 27°C in Luria broth (LB) containing the appropriate antibiotics, if necessary. Luminescent X. nematophilus.…”

Section: Methodsmentioning

confidence: 99%

“…Endotoxin of virulent and avirulent (AV1) X. nematophilus inhibits the activation of the opsonin phenoloxidase in the prophenoloxidase cascade in insect hemolymph (7). However, AV1 has a leaky outer membrane that releases periplasmic enzymes activating phenoloxidase (7).…”

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confidence: 99%

“…Since insect mortality occurs at a critical concentration of X. nematophilus (6), a density-dependent global regulator may initiate the release of toxic factors (7). Identification of such a regulator could provide the foundation for not only understanding but also controlling virulence of X. nematophilus, which in turn may lead to the development of more effective insect pathogens (11).…”

mentioning

confidence: 99%

“…The high susceptibility of many insect species to infection coupled with the strong reproductive capacity and mobility of the bacteriumnematode complex provides considerable potential for the use of parasitic nematodes for control of insects (11,14). Invasion of the nematodes into the hemocoel of susceptible insect larvae results in the release of the bacteria into the hemolymph; growth of the bacteria and nematodes then results in the rapid death of the insect larvae.Virulence of X. nematophilus and related insect-pathogenic bacteria is due to the expression of an interactive polygenic system comprising tolerance and evasion of the antimicrobial factors of the insect hemolymph (6, 15), changes in bacterial surfaces (6), and the excretion of toxic lipases and lecithinases (7,19). Since insect mortality occurs at a critical concentration of X. nematophilus (6), a density-dependent global regulator may initiate the release of toxic factors (7).…”

mentioning

confidence: 99%

“…Virulence of X. nematophilus and related insect-pathogenic bacteria is due to the expression of an interactive polygenic system comprising tolerance and evasion of the antimicrobial factors of the insect hemolymph (6, 15), changes in bacterial surfaces (6), and the excretion of toxic lipases and lecithinases (7,19). Since insect mortality occurs at a critical concentration of X. nematophilus (6), a density-dependent global regulator may initiate the release of toxic factors (7).…”

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A homoserine lactone autoinducer regulates virulence of an insect-pathogenic bacterium, Xenorhabdus nematophilus (Enterobacteriaceae)

1997

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N-␤-Hydroxybutanoyl homoserine lactone (HBHL), the autoinducer of the luminescent system of Vibrio harveyi, has been identified as the first small compound to restore virulence to avirulent mutants of Xenorhabdus nematophilus. HBHL stimulated the level of lipase activity excreted by avirulent X. nematophilus and lowered the phenoloxidase activity in the hemolymph of insects infected with X. nematophilus, parameters that are both associated with insect pathogenesis. Moreover, mortality of the insects infected with avirulent X. nematophilus was restored upon injection with HBHL. Chloroform extraction of medium conditioned with wild-type but not avirulent X. nematophilus led to the isolation of a compound with the same chromatographic mobility as HBHL as well as the ability to stimulate the luminescence of a dim autoinducer-dependent mutant of V. harveyi. Transfer of the V. harveyi lux operon into avirulent and wild-type X. nematophilus generated dim and bright luminescent strains, respectively, which responded to HBHL and an agonist and antagonist in a manner analogous to their effects on the luminescence of dim autoinducer-deficient and bright wild-type strains of V. harveyi, indicating that similar HBHL-dependent regulatory systems exist in these two bacterial species.Xenorhabdus nematophilus is a major insect pathogen that exists in the intestines of the parasitic nematode Steinernema carpocapsae (family Steinernematidae) (1, 9). The high susceptibility of many insect species to infection coupled with the strong reproductive capacity and mobility of the bacteriumnematode complex provides considerable potential for the use of parasitic nematodes for control of insects (11,14). Invasion of the nematodes into the hemocoel of susceptible insect larvae results in the release of the bacteria into the hemolymph; growth of the bacteria and nematodes then results in the rapid death of the insect larvae.Virulence of X. nematophilus and related insect-pathogenic bacteria is due to the expression of an interactive polygenic system comprising tolerance and evasion of the antimicrobial factors of the insect hemolymph (6, 15), changes in bacterial surfaces (6), and the excretion of toxic lipases and lecithinases (7,19). Since insect mortality occurs at a critical concentration of X. nematophilus (6), a density-dependent global regulator may initiate the release of toxic factors (7). Identification of such a regulator could provide the foundation for not only understanding but also controlling virulence of X. nematophilus, which in turn may lead to the development of more effective insect pathogens (11). This paper reports the discovery that the ␤-hydroxybutanoyl homoserine lactone (HBHL) autoinducer, which causes induction of luminescence in the marine bacterium Vibrio harveyi (4), can restore virulence to avirulent mutants of X. nematophilus. The present results also demonstrate that HBHL or a closely related analog is excreted by wild-type and not by avirulent X. nematophilus. MATERIALS AND METHODSStrains and growth conditi...

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

mentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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