Use Of The Entomopathogenic Nematode Symbiont Photorhabdus Luminescens As A Biocontrol Agent B-Factors Affecting The Cell-Free Filtrates From The Bacterium 1 (original) (raw)
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Catrina: The International Journal Of Environmental Sciences
Integrated Pest Management (IPM) is today a widely accepted strategy for reducing overdependence on chemical insecticides and to reduce their potentially negative environmental and economic effects. Photorhabdus is a gram-negative enteric bacterium that is found in association with entomopathogenic nematodes of the family Heterorhabditidae. The nematodes infect a variety of soil insect pests. Upon entering an insect host, the nematode releases Photorhabdus spp. cells from its intestinal tract, and the bacteria quickly establish a lethal septicemia. When grown in yeast salt broth, in the absence of the nematodes, the bacteria produce a toxin protein that is lethal when fed to the hemolymph of several insect species. Broth cultures of five isolates of Photorhabdus (A, B, C, D, E) were lethal to the nymphs of Galleria mellonella when mixed different concentrations (5,10 and 20 ml) from suspension bacterial cell with two kind of media (wheat bran and fine sand) as compared to broth alone (control). Results obtained showed that, after one day the mortality reached 100 % on sand inoculated with 20 ml cells suspension of the isolates A, C and D. A hyperbolic relationship was observed between different isolates, type of media, doses and time intervals. These bacterial cells were also recovered from the abdominal haemocoele indicating that bacterial symbionts do have a free-living existence and can enter in the haemocoele in the absence of nematode vector.
Journal of Zhejiang University Science, 2005
The entomopathogenic bacterium, Xenorhabdus nematophila was isolated from the hemolymph of Galleria mellonella infected with Steinernema carpocapsae. The bacterial cells and its metabolic secretions have been found lethal to the Galleria larvae. Toxic secretion in broth caused 95% mortality within 4 d of application whereas the bacterial cells caused 93% mortality after 6 d. When filter and sand substrates were compared, the later one was observed as appropriate. Similarly, bacterial cells and secretion in broth were more effective at 14% moisture and 25 °C temperature treatments. Maximum insect mortality (100%) was observed when bacterial concentration of 4×10 6 cells/ml was used. Similarly, maximum bacterial cells in broth (95%) were penetrated into the insect body within 2 h of their application. However, when stored bacterial toxic secretion was applied to the insects its efficacy declined. On the other hand, when the same toxic secretion was dried and then dissolved either in broth or water was proved to be effective. The present study showed that the bacterium, X. nematophila or its toxic secretion can be used as an important component of integrated pest management against Galleria.
2010
The oral toxicity of 5 Photorhabdus spp. strains collected in different regions of Korea was determined in the larvae of Plodia interpunctella, Galleria mellonella, Lucilia caesar, and Culex pipiens pallens. When diet or water containing culture media containing 1 of the 5 different strains was ingested by immature insects, the first instar larvae of both G. mellonella and L. caesar and young larvae of C. pipiens pallens died within 3-5 days after treatment. However, mortality of P. interpunctella neonate larvae was slightly slower and reached 94.4%-100% within 7 days after treatment. The mortality rate of a control group given a diet containing water, the medium without cultured bacteria, or Escherichia coli culture medium was not affected. The mortality rates were 100%, 45.3%, 2.8%, and 0% for Galleria, Lucilia, Plodia, and Culex, respectively, in another control group given a culture medium of Photorhabdus luminescens ssp. laumondii (TT01). In addition, culture media containing Photorhabdus strains significantly inhibited molting of third instar Plodia larvae by as much as 88% 7 days after treatment, whereas molting inhibition was reduced by 0%, 4%, and 20% following treatments with water, E. coli, or TT01 culture media, respectively. Our results suggest that the oral administration of Photorhabdus bacterial medium was highly effective for controlling various immature insects.
Journal of Plant Diseases and Protection, 2011
Entomopathogenic nematodes symbiotically associated with Photorhabdus spp. invade the larvae of susceptible insects and Photorhabdus bacteria are released into the insect hemolymph, which produce toxins and kill the insect larvae. In this study, five symbiotic bacteria isolates from soil nematodes, Heterorhabditis spp., have been reported. The bacteria were screened for insecticidal toxicity against larvae of Galleria mellonella. All were identified as different strains of Photorhabdus temperata via 16 s rDNA sequencing. The insecticidal activity was highest after 3-4 days of pure culture and the level of toxicity was higher in culture supernatant than in the cell pellet. The heat stability of the insecticidal activity was tested by heat treatments for 30 min at the range of 25°C to 100°C. Out of all isolated strains, P. temperata strains J4 and J5 produced heat-stable toxins. The supernatants extracted from the culture of these strains preserved up to 95% of insecticidal activity after heat treatment for 30 min at 80°C. The insecticidal activities of culture supernatants of all the selected strains were mostly maintained after proteinase K treatment. Based upon these findings, it can be inferred that the insecticidal toxins produced by Photorhabdus spp. were not pure protein substances.
International Journal of Experimental Research and Review, 2023
White grubs are a major polyphagous pest that imposes damage upon several plant species, mostly by feeding their roots. White grub larvae are one of the hazardous pests found in sugarcane. This problem causes a substantial drop in sugarcane crop productivity every year in India. In this research, white grub larvae were subjected to biocontrol using developed formulations of Photorhabdus bacteria, symbiotically associated with entomopathogenic nematodes under laboratory conditions. The Photorhabdus bacteria isolated from entomopathogenic nematode- Heterorhabditis indica have insecticidal activity towards insect pests by exerting an array of toxic effects. The main insecticidal activity, i.e., chitinase enzyme production by these bacteria, was associated with mortality of insect pests. In the present investigation, chitinase production by Photorhabdus bacteria was determined by DEAE column chromatography. The various bacterial formulations of Photorhabdus were examined for their insecticidal activity against the white grub larvae under laboratory conditions. Mortality of the white grub larvae was observed after 24–48 hours of exposure. The formulations of Photorhabdus showed statistically significant effects on mortality of larvae. The percent mortality of larvae after treatment with formulation 3 was highly significant compared to those treated with formulation 1 and 2. Formulation 3 expressed a significantly lower LD50 value, i.e., 121.31 CFU/mL, over formulations 1 and 2, i.e., 127.34 & 133.56 CFU/mL, respectively. Formulation 3 showed greater efficacy in killing white grub larvae at lower concentrations. The formulation 3 of Photorhabdus bacteria has great potential to kill white grub larvae under laboratory conditions and requires further evaluation for its promising use as a biocontrol agent by pot and field studies.
Assesment Of The Antagonistic Potential For The Bacterial Symbionts Of Entomopathogenic Nematodes
2012
Ten separate isolates of the entomopathogenic nematode-symbiotic bacteria, eight designed as Photorhabdus luminescens A, C, D, E, F, Kh1, Kh2, and HB and two isolates as P. luminescens akhurstii B and H, were obtained from the haemolymph of last instar Galleria mellonella larvae inoculated with infective juveniles of their corresponding Egyptian entomopathogenic nematode isolates, Heterorhabditis bacteriophora and H. indica. The bacterium-free filtrates were evaluated by mycelial plug on NBTA plates and a paper disc diffusion assays for their antifungal and antibacterial activity, respectively, against fifteen soil microorganisms. The tested fungi were Trichoderma harzianum, T. reesi, T. viride, T. reesi F418, Aspergillus flavus, A. niger, Fusarium solani, Saccharomyces cerevisiae. The tested bacteria were Bacillus subtillus, B. megatherm var phosphaticum, Staphylococcus aureus, Streptomycetes spp., Pseudomonas fluorescens, Rhizobium leguminosarum, Salmonella typhemurium. Growth of ...
Journal of Asia-Pacific Entomology, 2017
Entomopathogenic nematodes are key players for insect pest control and constitute an environmentally friendly alternative for crop protection. The insecticidal activity of the family Heterorhabditidae relies on a tight symbiotic relationship with enterobacteria of the genus Photorhabdus, where the bacterial contribution towards the death of the host has been highlighted. In the present work, we report the identification and pathogenic characterization of Photorhabdus luminescens strain SL0708, which is the natural symbiont of Heterorhabditis indica SL0708. We evaluated the pathogenicity of whole bacterial cells and acellular extracts against both Spodoptera frugiperda larvae and Galleria mellonella. Phylogenetic analyses using a polygenic sequencing approach assigned the bacterial strain to Photorhabdus luminescens subsp. akhurstii and bioassays showed it is highly pathogenic for both insects. After 48 h of treatment with 1 × 10 3 − 1 × 10 4 CFU/larva, 100% mortality was attained. Furthermore, when intra-or extracellular bacterial extracts were injected into G. mellonella, a cumulative percent mortality of 63% and 100% was respectively obtained after 72 h. In contrast, a 10% and 93% mortality was achieved for S. frugiperda with intra and extracellular extracts, respectively highlighting the role of extracellular factors in pathogenicity. We detected extracellular activities potentially accounting for the high pathogenicity observed and these included; proteases, esterases, ureases, hemolysins and siderophores. Interestingly, S. frugiperda was more susceptible to P. luminescens SL0708 cells than G. mellonella, which contrasted to its higher resistance to H. indica SL0708 nematodes, which suggests that EPN biological control potential should also be evaluated based on bacterial symbiont pathogenicity.
Canadian Journal of Microbiology, 2011
Three bacteria, Alcaligenes faecalis, Flavobacterium sp., and Providencia vermicola, were isolated from dauer juveniles of Rhabditis blumi. The pathogenic effects of the bacteria against 4th instar larvae of Galleria mellonella were investigated. Providencia vermicola and Flavobacterium sp. showed 100% mortality at 48 h after haemocoelic injection, whereas A. faecalis showed less than 30% mortality. Dauer juveniles showed 100% mortality against G. mellonella larvae, whereas axenic juveniles, which do not harbor associated bacteria, exhibited little mortality. All of the associated bacteria were used as a food source for nematode growth, and nematode yield differed with bacterial species. Among the bacterial species, P. vermicola was most valued for nematode yield, showing the highest yield of 5.2 × 10 4 nematodes/mL in the plate. In bacterial cocultures using two of the three associated bacteria, one kind stimulated the other. The highest total bacterial yield of 12.6 g/L was obtained when the inoculum ratio of P. vermicola to A. faecalis was 10:1. In airlift bioreactors, the nematode growth rate increased with an increasing level of dissolved oxygen. The maximum nematode yield of 1.75 × 10 5 nematodes/mL was obtained at 192 h with an aeration rate of 6 vvm.
The Journal of General and Applied Microbiology, 1996
An antifoaming agent was produced by strains of Xenorhabdus nematophilus independent of the type of medium and lipid supplementation. The antifoam was heat stable and susceptible to inactivation at moderately acidic (pH 4-6) and alkaline (pH 7.5-8.0) values. The agent was soluble in chloroform and chloroform-methanol suspensions, resistant to proteolytic digestion, negatively-charged and hydrophobic and may be a lipopeptide. The level of antifoam varied with the bacterial strain and was not correlated with the onset of the stationary phase of strain OP 1-7 but it peaked during the early stationary phase for strain 19061. Antifoam release into broth required metabolizing cells and was associated with whole bacterial cells. Nematode growth, reproduction and infective juvenile production was enhanced by the antifoam. Because surfactants conducive to the dispersal of lipids produced similar effects, it is possible that the bacterial antifoam enhanced nematode nutrition directly by increasing the availability of lipids to the animals or indirectly by increasing bacterial activity.