Effect of antibiotics on the insecticidal activity of Bacillus thuringiensis

Ignoffo, Carlo M.; Garcia, C.; Couch, T. L.

doi:10.1016/0022-2011(77)90236-1

Cited by 15 publications

(9 citation statements)

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“…It is noteworthy that the antibiotic attenuation of B. thuringiensis was observed after using two antibiotics at lower concentrations than those used in similar studies (6,7), which used gentamicin, penicillin, rifampin, and streptomycin each at 500 g ml Ϫ1 of diet. It is known that dietary antibiotics can attenuate the toxicity of B. thuringiensis spore-crystal mixtures to many lepidopterans (5,16,17,19,21,25) and that such attenuation can eliminate spore synergism, leaving only the effect of Cry toxins (25,32). Therefore, it is proposed that a direct effect of residual antibiotics or an indirect effect such as an induction of a host xenobiotic detoxification response could reduce or eliminate any synergism associated with the germination of B. thuringiensis spores, leaving only the effect of Cry toxins.…”

Section: Discussionmentioning

confidence: 99%

Gut Bacteria Are Not Required for the Insecticidal Activity of Bacillus thuringiensis toward the Tobacco Hornworm, Manduca sexta

Johnston

Crickmore

2009

Appl Environ Microbiol

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It was recently proposed that gut bacteria are required for the insecticidal activity of the Bacillus thuringiensis-based insecticide, DiPel, toward the lepidopterans Manduca sexta, Pieris rapae, Vanessa cardui, and Lymantria dispar. Using a similar methodology, it was found that gut bacteria were not required for the toxicity of DiPel or Cry1Ac or for the synergism of an otherwise sublethal concentration of Cry1Ac toward M. sexta. The toxicities of DiPel and of B. thuringiensis HD73 Cry ؊ spore/Cry1Ac synergism were attenuated by continuously exposing larvae to antibiotics before bioassays. Attenuation could be eliminated by exposing larvae to antibiotics only during the first instar without altering larval sterility. Prior antibiotic exposure did not attenuate Cry1Ac toxicity. The presence of enterococci in larval guts slowed mortality resulting from DiPel exposure and halved Cry1Ac toxicity but had little effect on B. thuringiensis HD73 Cry ؊ spore/Cry1Ac synergism. B. thuringiensis Cry ؊ cells killed larvae after intrahemocoelic inoculation of M. sexta, Galleria mellonella, and Spodoptera litura and grew rapidly in plasma from M. sexta, S. litura, and Tenebrio molitor. These findings suggest that gut bacteria are not required for B. thuringiensis insecticidal activity toward M. sexta but that B. thuringiensis lethality is reduced in larvae that are continuously exposed to antibiotics before bioassay.Bacillus thuringiensis has long been regarded as a bona fide entomopathogen that can produce an array of virulence factors including insecticidal parasporal crystal (Cry) toxins, vegetative insecticidal proteins, phospholipases, immune inhibitors, and antibiotics (31). B. thuringiensis establishes lethal infections in many insect species after intrahemocoelic inoculation (9,10,14,26,31), and the insecticidal activity of Cry toxins, which lyse the intestinal epithelium, can be synergized by the presence of viable B. thuringiensis spores (31). In each instance, synergism has been attributed to hemocoelic infection by B. thuringiensis.A novel hypothesis (6, 7) proposed that B. thuringiensis is incapable of killing Lymantria dispar, Manduca sexta, Pieris rapae, or Vanessa cardui in the absence of gut bacteria. Prior exposure of L. dispar larvae to a combination of four antibiotics severely reduced the subsequent toxicity of the B. thuringiensis-based (spores and Cry toxins) bioinsecticide, DiPel (Valent BioSciences) (6). Both larval susceptibility to B. thuringiensis and the number of culturable gut bacteria were found to be negatively correlated with the concentration of antibiotics to which larvae were previously exposed. Furthermore, a total reduction in larval susceptibility was coincident with the elimination of any detectable gut bacteria. Experimental reinfection with Enterobacter sp. strain NAB3, found in the guts of some populations of L. dispar larvae, was found to rescue the toxicity of B. thuringiensis, whereas reinfection with Enterococcus casseliflavus and Staphylococcus xylosus did not. It was also sho...

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Section: Discussionmentioning

confidence: 99%

Gut Bacteria Are Not Required for the Insecticidal Activity of Bacillus thuringiensis toward the Tobacco Hornworm, Manduca sexta

Johnston

Crickmore

2009

Appl Environ Microbiol

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“…Interestingly, the involvement of gut microbiota seems to be species-dependent [ 24 ]. In contrast, some scientists argued that the observed effect is mainly due to the residual antibiotic effect on Bt, resulting in a biased outcome of the experiments [ 7 , 25 , 26 ]. Additional studies performed by other groups found no experimental support for microbiota involvement in Bt toxicity, even on similar insect species [ 14 , 21 , 27 , 28 ].…”

Section: Introductionmentioning

confidence: 99%

Bacterial microbiota of Aedes aegypti mosquito larvae is altered by intoxication with Bacillus thuringiensis israelensis

et al. 2018

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BackgroundInsect microbiota is a dynamic microbial community that can actively participate in defense against pathogens. Bacillus thuringiensis (Bt) is a natural entomopathogen widely used as a bioinsecticide for pest control. Although Bt’s mode of action has been extensively studied, whether the presence of microbiota is mandatory for Bt to effectively kill the insect is still under debate. An association between a higher tolerance and a modified microbiota was already evidenced but a critical point remained to be solved: is the modified microbiota a cause or a consequence of a higher tolerance to Bt?MethodsIn this study we focused on the mosquito species Aedes aegypti, as no work has been performed on Diptera on this topic to date, and on B. thuringiensis israelensis (Bti), which is used worldwide for mosquito control. To avoid using antibiotics to cure bacterial microbiota, mosquito larvae were exposed to an hourly increasing dose of Bti during 25 hours to separate the most susceptible larvae dying quickly from more tolerant individuals, with longer survival.ResultsDenaturing gradient gel electrophoresis (DGGE) fingerprinting revealed that mosquito larval bacterial microbiota was strongly affected by Bti infection after only a few hours of exposure. Bacterial microbiota from the most tolerant larvae showed the lowest diversity but the highest inter-individual differences. The proportion of Bti in the host tissue was reduced in the most tolerant larvae as compared to the most susceptible ones, suggesting an active control of Bti infection by the host.ConclusionsHere we show that a modified microbiota is associated with a higher tolerance of mosquitoes to Bti, but that it is rather a consequence of Bti infection than the cause of the higher tolerance. This study paves the way to future investigations aiming at unraveling the role of host immunity, inter-species bacterial competition and kinetics of host colonization by Bti that could be at the basis of the phenotype observed in this study.Electronic supplementary materialThe online version of this article (10.1186/s13071-018-2741-8) contains supplementary material, which is available to authorized users.

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“…We used the antibiotic streptomycin (Sigma) to block germination of spores in spore-crystal formulations of B. thuringiensis. Inhibition of germination of B. thuringiensis spores by streptomycin has been demonstrated in several studies (2,13,14). To determine an appropriate concentration of streptomycin, we tested streptomycin at 0 (control), 10, 100, and 1,000 mg/liter against susceptible (LAB-P) larvae with and without spores from B. thuringiensis subsp.…”

Section: Methodsmentioning

confidence: 99%

Synergism between Bacillus thuringiensis Spores and Toxins against Resistant and Susceptible Diamondback Moths ( Plutella xylostella )

Liu

Tabashnik

Moar

et al. 1998

Appl Environ Microbiol

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We studied the effects of combinations of Bacillus thuringiensis spores and toxins on the mortality of diamondback moth (Plutella xylostella) larvae in leaf residue bioassays. Spores of B. thuringiensis subsp.kurstaki increased the toxicity of crystals of B. thuringiensis subsp. kurstaki to both resistant and susceptible larvae. For B. thuringiensis subsp.kurstaki, resistance ratios were 1,200 for a spore-crystal mixture and 56,000 for crystals without spores. Treatment of a spore-crystal formulation of B. thuringiensissubsp. kurstaki with the antibiotic streptomycin to inhibit spore germination reduced toxicity to resistant larvae but not to susceptible larvae. In contrast, analogous experiments withB. thuringiensis subsp.aizawai revealed no significant effects of adding spores to crystals or of treating a spore-crystal formulation with streptomycin. Synergism occurred between Cry2A and B. thuringiensis subsp. kurstaki spores against susceptible larvae and between Cry1C and B. thuringiensis subsp. aizawai spores against resistant and susceptible larvae. The results show thatB. thuringiensis toxins combined with spores can be toxic even though the toxins and spores have little or no independent toxicity. Results reported here and previously suggest that, for diamondback moth larvae, the extent of synergism between spores and toxins of B. thuringiensis depends on the strain of insect, the type of spore, the set of toxins, the presence of other materials such as formulation ingredients, and the concentrations of spores and toxins.

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Effect of antibiotics on the insecticidal activity of Bacillus thuringiensis

Cited by 15 publications

References 0 publications

Gut Bacteria Are Not Required for the Insecticidal Activity of Bacillus thuringiensis toward the Tobacco Hornworm, Manduca sexta

Gut Bacteria Are Not Required for the Insecticidal Activity of Bacillus thuringiensis toward the Tobacco Hornworm, Manduca sexta

Bacterial microbiota of Aedes aegypti mosquito larvae is altered by intoxication with Bacillus thuringiensis israelensis

Synergism between Bacillus thuringiensis Spores and Toxins against Resistant and Susceptible Diamondback Moths ( Plutella xylostella )

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