Gut bacteria not required for Bacillus thuringiensis insecticidal activity towards the tobacco hornworm, Manduca sexta

Johnston, Paul R and Crickmore, Neil (2009) Gut bacteria not required for Bacillus thuringiensis insecticidal activity towards the tobacco hornworm, Manduca sexta. Applied and Environmental Microbiology, 75 (15). pp. 5094-5099. ISSN 0099-2240

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Abstract

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.

Item Type: Article
Schools and Departments: School of Life Sciences > Biochemistry
Subjects: Q Science
Depositing User: Paul Ronald Johnston
Date Deposited: 06 Feb 2012 21:29
Last Modified: 03 Oct 2012 12:48
URI: http://srodev.sussex.ac.uk/id/eprint/31469
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