The fate of Bacillus thuringiensis var. israelensis in B. thuringiensis var. israelensis-killed pupae of Aedes aegypti

Kamal Khawaled, Eitan Ben-Dov, Arieh Zaritsky, Ze'ev Barak

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Carcasses of mosquito larvae killed by Bacillus thuringiensis var. israelensis allow its complete growth cycle (germination, vegetative growth, and sporulation), thus becoming toxic themselves to scavenging larvae. In this study, we demonstrate that the bacterium is capable of inducing death of Aedes aegypti pupae and of recycling in the resulting carcasses. B. thuringiensis var. israelensis-killed pupae were obtained by treating 40-hr-old synchronized fourth instar larvae with a low dose of spores (8000/ml). The fraction of dead pupae was reduced by higher or lower spore concentrations as well as by treating younger or older larval populations (both fourth instar): Increased proportions of dead larvae were obtained at higher concentration or by earlier treatment, whereas lower concentrations or later treatment resulted in more living pupae. Multiplication of B. thuringiensis var. israelensis is shown to occur in the carcasses of dead pupae. The number of spores in each pupal carcass followed a similar kinetic as in larval carcasses, but the final yield was about 10-fold higher, apparently reflecting the difference in dry weight between the two mosquito developmental stages (426 μg vs 83 μg, respectively). The specific larvicidal activity in a homogenized dead pupa was similar to that of B. thuringiensis var. israelensis powder, LC50 of about 600 spores/ml.

Original languageEnglish
Pages (from-to)312-316
Number of pages5
JournalJournal of Invertebrate Pathology
Volume56
Issue number3
DOIs
StatePublished - 1 Jan 1990

Keywords

  • Aedes aegypti larvae
  • Bacillus thuringiensis var. israelenis
  • pupicidal activity
  • spore recycling
  • δ-endotoxin

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics

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