Differences between the pathogenic processes induced by Steinernema and Heterorhabditis (Nemata: Rhabditida) in Pseudaletia unipuncta (Insecta: Lepidoptera)

Rosa, José S.; Cabral, C; Simões, Nélson

doi:10.1016/s0022-2011(02)00038-1

Cited by 20 publications

(18 citation statements)

References 32 publications

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“…Caroli et al (1996) showed that the penetration rate in heterorhabdı´tids is lower than in steinernematids infecting different insects. Rosa et al (2002) also observed a larger number of S. carpocapsae invaded larvae of the armyworm Pseudaletia unipuncta (Lepidoptera: Noctuidae) than H. bacteriophora. However, in our study Steinernema sp.…”

Section: Discussionmentioning

confidence: 83%

Laboratory efficacy against neonate larvae of the banana weevilCosmopolites sordidusof two indigenous entomopathogenic nematode species from the Canary Islands (Spain)

Padilla-Cubas

Hernández

Pino

2010

International Journal of Pest Management

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We evaluated the efficacy, against neonate larvae of the banana weevil, Cosmopolites sordidus (Germar) (Coleoptera, Curculionidae), of two indigenous entomopathogenic nematode species of the families Steinernematidae and Heterorhabditidae. The nematodes, isolated in the Canary Islands (Spain), were Heterorhabditis bacteriophora (TF19) and an undescribed species (TF135) of the Steinernema feltiae-group. Exposure of C. sordidus neonate larvae to 5 concentrations (2.5, 5, 25, 50 and 100 infective juveniles/cm 2 ) in Petri dishes with sterile sand resulted in 100% mortality, with each of the two nematode species at all concentrations tested. The lowest median lethal time (LT 50 ) for Steinernema sp. was 2.6 d at a dose of 25 infective juveniles/cm 2 and 3.6 d for H. bacteriophora at a dose of 2.5 and 5 infective juveniles/cm 2 . The penetration rate was also evaluated as an indicator of entomopathogenic nematode infectivity. The highest values for penetration rate were recorded at lowest concentrations of infection in Steinernema sp. and in H. bacteriophora, but rates differed regardless of the LT 50 . Our results suggest that these two nematode species may improve the biological control of neonate larvae of C. sordidus in banana crops.

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Section: Discussionmentioning

confidence: 83%

Laboratory efficacy against neonate larvae of the banana weevilCosmopolites sordidusof two indigenous entomopathogenic nematode species from the Canary Islands (Spain)

Padilla-Cubas

Hernández

Pino

2010

International Journal of Pest Management

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“…The species X. poinarii has been described as weakly virulent following its direct injection into insect hemolymph (Akhurst 1986; Converse and Grewal 1998; Rosa et al 2002; Ansari et al 2003). We investigated the virulence of X. poinarii strains AZ26 ( Xp_AZ26 ), CU01 ( Xp_CU01 ), Xp_G6 , NC33 ( Xp_NC33 ) and SK72 ( Xp_SK72 ) in insect larvae, by injecting 1,000 bacterial cells/larva directly into the hemocoel of S p .…”

Section: Resultsmentioning

confidence: 99%

“…By contrast, the St . glaseri – Xenorhabdus poinarii couple is virulent principally in a few coleopteran species, such as Popillia japonica and Cyclocephala hirta , suggesting a potentially narrow host specificity (Wang et al 1994; Converse and Grewal 1998; Rosa et al 2002; Fallon et al 2006). …”

Section: Introductionmentioning

confidence: 99%

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Attenuated Virulence and Genomic Reductive Evolution in the Entomopathogenic Bacterial Symbiont Species, Xenorhabdus poinarii

Ogier

Pagès

Bisch

et al. 2014

Genome Biology and Evolution

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Bacteria of the genus Xenorhabdus are symbionts of soil entomopathogenic nematodes of the genus Steinernema. This symbiotic association constitutes an insecticidal complex active against a wide range of insect pests. Unlike other Xenorhabdus species, Xenorhabdus poinarii is avirulent when injected into insects in the absence of its nematode host. We sequenced the genome of the X. poinarii strain G6 and the closely related but virulent X. doucetiae strain FRM16. G6 had a smaller genome (500–700 kb smaller) than virulent Xenorhabdus strains and lacked genes encoding potential virulence factors (hemolysins, type 5 secretion systems, enzymes involved in the synthesis of secondary metabolites, and toxin–antitoxin systems). The genomes of all the X. poinarii strains analyzed here had a similar small size. We did not observe the accumulation of pseudogenes, insertion sequences or decrease in coding density usually seen as a sign of genomic erosion driven by genetic drift in host-adapted bacteria. Instead, genome reduction of X. poinarii seems to have been mediated by the excision of genomic blocks from the flexible genome, as reported for the genomes of attenuated free pathogenic bacteria and some facultative mutualistic bacteria growing exclusively within hosts. This evolutionary pathway probably reflects the adaptation of X. poinarii to specific host.

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“…Photorhabdus sp. strain Az29 proved to be the most pathogenic against sixthinstar larvae of P. unipuncta, with a median lethal time of 40.6 h after injection of 200 CFU (42). These data enhanced our interest in the virulence factors released by Photorhabdus sp.…”

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confidence: 68%

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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Differences between the pathogenic processes induced by Steinernema and Heterorhabditis (Nemata: Rhabditida) in Pseudaletia unipuncta (Insecta: Lepidoptera)

Cited by 20 publications

References 32 publications

Laboratory efficacy against neonate larvae of the banana weevilCosmopolites sordidusof two indigenous entomopathogenic nematode species from the Canary Islands (Spain)

Laboratory efficacy against neonate larvae of the banana weevilCosmopolites sordidusof two indigenous entomopathogenic nematode species from the Canary Islands (Spain)

Attenuated Virulence and Genomic Reductive Evolution in the Entomopathogenic Bacterial Symbiont Species, Xenorhabdus poinarii

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

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