Active resistance of entomophagous rhabditid Heterorhabditis bacteriophora to insect immunity

Jarosz, J.

doi:10.1017/s0031182098003011

Cited by 33 publications

(13 citation statements)

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“…In initial studies, this ability was attributed to the nematode, but Photorhabdus by itself multiplies rapidly escaping insect defenses (13,15). In insects infected with the nematode-bacterium complex, soluble immunodepression factors were found, suggesting that proteases could be mediators of this activity (28). In the present study we have shown that PrtA and PrtS inhibited the antibacterial activity, particularly in the in vitro cecropin A and B assays.…”

Section: Discussionsupporting

confidence: 47%

Purification and Characterization of Two Distinct Metalloproteases Secreted by the Entomopathogenic Bacterium Photorhabdus sp. Strain Az29

Cabral

Cherqui

Pereira

et al. 2004

Appl Environ Microbiol

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Photorhabdus sp. strain Az29 is symbiotic with an Azorean nematode of the genus Heterorhabditis in a complex that is highly virulent to insects even at low temperatures. The virulence of the bacteria is mainly attributed to toxins and bacterial enzymes secreted during parasitism. The bacteria secrete proteases during growth, with a peak at the end of the exponential growth phase. Protease secretion was higher in cultures growing at lower temperatures. At 10°C the activity was highest and remained constant for over 7 days, whereas at 23 and 28°C it showed a steady decrease. Two proteases, PrtA and PrtS, that are produced in the growth medium were purified by liquid chromatography. PrtA was inhibited by 1,10-phenantroline and by EDTA and had a molecular mass of 56 kDa and an optimal activity at pH 9 and 50°C. Sequences of three peptides of PrtA showed strong homologies with alkaline metalloproteases from Photorhabdus temperata K122 and Photorhabdus luminescens W14. Peptide PrtA-36 contained the residues characteristic of metzincins, known to be involved in bacterial virulence. In vitro, PrtA inhibited antibacterial factors of inoculated Lepidoptera and of cecropins A and B. PrtS had a molecular mass of 38 kDa and was inhibited by 1,10-phenanthroline but not by EDTA. Its activity ranged between 10 and 80°C and was optimal at pH 7 and 50°C. PrtS also destroyed insect antibacterial factors. Three fragments of PrtS showed homology with a putative metalloprotease of P. luminescens TTO1. Polyclonal antibody raised against PrtA did not recognize PrtS, showing they are distinct molecules.Photorhabdus spp. are non-free-living Enterobacteriaceae (6, 19). The entomopathogen species of Photorhabdus have a symbiotic relation with nematodes of the genus Heterorhabditis for transport with their infective juveniles (IJs). The IJs actively seek for an insect host, penetrating through its natural openings and cuticle. Inside the insect hemocoel, the bacteria are released and actively multiply avoiding the host defenses and causing an acute disease condition that is followed by insect death within 48 h. The bacteria also create the nutritional conditions and protective environment for the development of its nematode symbiont (2, 21).Bacteria of the Photorhabdus genus produce toxins and other potentially virulent factors (16). The characterized toxins are organized in pathogenic islands (53) and include the Tc complex, which is responsible for oral toxicity (9, 52), and the Mcf toxin, which causes loss of insect body turgor, followed by death (14). Among other potential virulence factors, there is a complex set of extracellular enzymes, including proteases, lipases, lecithinases, chitinases, and phosphatases (5,12,20). Proteases represent an important part of these enzymes, although their role on the virulence process is yet unclear. Until now, all extracellular proteases purified and characterized from Photorhabdus were classified as metalloproteases, but in reports on proteases from different strains it has been suggested that ther...

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Section: Discussionsupporting

confidence: 47%

Purification and Characterization of Two Distinct Metalloproteases Secreted by the Entomopathogenic Bacterium Photorhabdus sp. Strain Az29

Cabral

Cherqui

Pereira

et al. 2004

Appl Environ Microbiol

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“…Most insect antibacterial peptides are rich in Lys and Arg residues, the targets of trypsin-like peptidases. In addition, cecropin is degraded by enzymes produced specifically for this purpose by Bacillus larvae, Heterorhabditis bacteriophora and P. aeruginosa [109][110][111]. Attacins are destroyed by inhibitor A, an exoprotease produced by Bacillus thuringiensis at the beginning of the stationary growth phase [112].…”

Section: Stability and In Vivo Propertiesmentioning

confidence: 99%

Antibacterial peptides isolated from insects

2000

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“…within their intestine. Once a suitable host has been penetrated, the bacteria are released into the host's body cavity where they disable the immune system and cause the death of the host by septicaemia, usually within 48 h (Jarosz, 1998). This process creates a favourable environment for nematode growth and reproduction and enables the IJs to continue development through to adulthood.…”

Section: Introductionmentioning

confidence: 99%

Density-dependent fecundity and infective juvenile production in the entomopathogenic nematode, Heterorhabditis megidis

Ryder

Griffin

2002

Parasitology

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summaryThe entomopathogenic nematode Heterorhabditis megidis may undergo several rounds of reproduction within a single host. Infective juveniles (IJs) are formed within each generation during a process referred to as endotokia matricida, which involves the progressive consumption of the parent hermaphrodite or female by the developing IJs prior to emergence from the host cadaver. The present study examines the extent to which within-host population dynamics exhibit densitydependent variation. Particular attention is paid to the effect of infection density on the relative production of IJs and ' normal ', non-infective offspring within each generation and on the emergence of the IJs from the host. Fecundity was found to be negatively density dependent across generations. However, at high infection density the first generation hermaphrodites invested relatively more in IJs at the expense of producing non-infective offspring. It is suggested that this pattern resulted from an adaptive, phenotypically plastic allocation of reproductive investment between offspring types in response to increased competition. The F " and F # IJs were also shown to emerge from the host in relatively discrete pulses.

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Active resistance of entomophagous rhabditid Heterorhabditis bacteriophora to insect immunity

Cited by 33 publications

References 0 publications

Purification and Characterization of Two Distinct Metalloproteases Secreted by the Entomopathogenic Bacterium Photorhabdus sp. Strain Az29

Purification and Characterization of Two Distinct Metalloproteases Secreted by the Entomopathogenic Bacterium Photorhabdus sp. Strain Az29

Antibacterial peptides isolated from insects

Density-dependent fecundity and infective juvenile production in the entomopathogenic nematode, Heterorhabditis megidis

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