Occurrence of Natural
            <i>Bacillus thuringiensis</i>
            Contaminants and Residues of
            <i>Bacillus thuringiensis</i>
            -Based Insecticides on Fresh Fruits and Vegetables

Frederiksen, Kirsten; Rosenquist, Hanne; Jørgensen, Kirsten; Wilcks, Andrea

doi:10.1128/aem.72.5.3435-3440.2006

Cited by 71 publications

(51 citation statements)

References 28 publications

(37 reference statements)

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“…1×10 5 colony forming units (CFU)/g (Frederiksen et al, 2006;Stephan et al, 2014) and the application doses recommended by the manufacturers of Btk bioinsecticides, i.e. 5×10 5 to 2.5×10 6 CFU/cm² depending on the type of crop to treat.…”

Section: Resultsmentioning

confidence: 99%

Apoptosis restores cellular density by eliminating a physiologically or genetically induced excess of enterocytes in the Drosophila midgut

et al. 2017

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Using pathogens or high levels of opportunistic bacteria to damage the gut, studies in Drosophila have identified many signaling pathways involved in gut regeneration. Dying cells emit signaling molecules that accelerate intestinal stem cell proliferation and progenitor differentiation to replace the dying cells quickly. This process has been named 'regenerative cell death'. Here, mimicking environmental conditions, we show that the ingestion of low levels of opportunistic bacteria was sufficient to launch an accelerated cellular renewal program despite the brief passage of bacteria in the gut and the absence of cell death and this is is due to the moderate induction of the JNK pathway that stimulates stem cell proliferation. Consequently, the addition of new differentiated cells to the gut epithelium, without preceding cell loss, leads to enterocyte overcrowding. Finally, we show that a couple of days later, the correct density of enterocytes is promptly restored by means of a wave of apoptosis involving Hippo signaling and preferential removal of old enterocytes.

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Section: Resultsmentioning

confidence: 99%

Apoptosis restores cellular density by eliminating a physiologically or genetically induced excess of enterocytes in the Drosophila midgut

et al. 2017

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“…g 21 from cabbage products (Hendriksen & Hansen, 2006) to .10 4 c.f.u. g 21 on cucumbers and cherry tomatoes (Frederiksen et al, 2006). The infective dose of B. cereus diarrhoeal syndrome is 10 5 -10 8 total cells or spores (Stenfors Arnesen et al, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…The infective dose of B. cereus diarrhoeal syndrome is 10 5 -10 8 total cells or spores (Stenfors Arnesen et al, 2008). Frederiksen et al (2006) postulated that it is therefore conceivable that a human could consume an infective dose from such produce. A recent report analysed B. cereus-group strains isolated from 39 food poisoning outbreaks and determined that in four of the outbreaks only B. thuringiensis isolates were recovered from food samples (McIntyre et al, 2008), suggesting that B. thuringiensis can be responsible for food poisoning when B. cereus is implicated, because isolates are not routinely examined for the presence of crystal toxin genes or proteins (Granum, 2002;European Food Safety Authority, 2005 For many years, B. thuringiensis bioinsecticides have been considered safe and effective despite the presence of enterotoxin genes.…”

Section: Discussionmentioning

confidence: 99%

“…On: Fri, 11 May 2018 22:33:03 debate in the scientific community about whether B. thuringiensis on produce could cause food poisoning (Damgaard, 1995;Hansen & Hendriksen, 2001;Frederiksen et al, 2006, Rosenquist et al, 2005Kyei-Poku et al, 2007). Early toxicology studies of B. thuringiensis included tests on human volunteers who ingested 1 g (3610 9 B. thuringiensis spores) of the commercial product Thuricide daily for 5 days without any adverse health effects (Fisher and Rosner, 1959).…”

Section: Introductionmentioning

confidence: 99%

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A quadruple-enterotoxin-deficient mutant of Bacillus thuringiensis remains insecticidal

2010

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Bacillus thuringiensis is the leading biopesticide used to control insect pests worldwide. Although they have a long record of safe use, under certain conditions commercial strains of B. thuringiensis have the ability to produce numerous putative enterotoxins that have been associated with food poisoning attributed to Bacillus cereus. Therefore, we designed a strategy to delete the genes encoding these toxins. B. thuringiensis strain VBTS 2477 contained genes encoding NHE, CytK-2 and three homologues of haemolysin BL (HBL, HBL a1 and HBL a2 ). This is the first report, to our knowledge, of a strain of B. cereus or B. thuringiensis containing three sets of hbl operons. The genes encoding HBL a1 and HBL a2 were 96-97 % identical to each other and 76-84 % identical to those encoding HBL. The hbl a2 operon was detected by PCR amplification only after hbl a1 was deleted. We used sequential gene replacement to replace the wild-type copies of the NHE and three HBL operons with copies that contained internal deletions that span the three genes in each operon. The insecticidal activity of the quadruple-enterotoxin-deficient mutant was similar to that of the wild-type strain against larvae of Trichoplusia ni, Spodoptera exigua and Plutella xylostella. This demonstrates that the genes for enterotoxins can be deleted, eliminating the possibility of enterotoxin production without compromising the insecticidal efficacy of a strain of B. thuringiensis. INTRODUCTIONBacillus thuringiensis has been used globally for over 50 years as a bioinsecticide for the control of insect pests in agriculture, forestry and public health. B. thuringiensis produces one or more crystal proteins during sporulation that are toxic to insect larvae upon ingestion. The toxins exhibit a narrow host spectrum, with an individual toxin typically affecting a subset of species within an insect order (Lepidoptera, Diptera, Coleoptera). Numerous studies show B. thuringiensis to be harmless to humans and mammals (Fisher & Rosner, 1959; US Environmental Protection Agency, 1998) and it has become increasingly popular as a method of insect control that is more environmentally friendly than synthetic chemical insecticides.B. thuringiensis is a Gram-positive spore-forming bacterium that is a member of the Bacillus cereus group. Phylogenetic studies and whole-genome sequencing reveal that B. thuringiensis and B. cereus are members of the same species group (Carlson et al., 1994;Helgason et al., 2000;Hill et al., 2004;Rasko et al., 2005). Both B. thuringiensis and B. cereus are found in soils, in the guts of invertebrates and associated with plants (Smith & Couche, 1991; Margulis et al., 1998;Martin & Travers, 1989;Jensen et al., 2003;Jara et al., 2006;Bizzarri & Bishop, 2007), and the only distinguishing phenotype is the production in B. thuringiensis of plasmid-encoded crystal toxins upon sporulation. Some strains of B. cereus are known to be foodpoisoning agents and opportunistic pathogens (Kotiranta et al., 2000). Pathogenic strains of B. cereus are responsibl...

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“…Conjugation, mobilization, and retromobilization were detected in all food types, emphasizing their possible ecological impact from contributing to the transfer and accumulation of harmful genetic traits, such as virulence or antibiotic resistance genes, among foodborne bacteria. It is important to keep in mind that bacteria such as B. thuringiensis are used as biopesticides on crops and could therefore be recovered in the food chain (15).…”

Section: Discussionmentioning

confidence: 99%

Plasmid Capture by the Bacillus thuringiensis Conjugative Plasmid pXO16

et al. 2009

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Conjugation, mobilization, and retromobilization are three related mechanisms of horizontal gene transfer in bacteria. They have been extensively studied in gram-negative species, where retromobilization, the capture of DNA from a recipient by a donor cell, was shown to result from two successive steps: the transfer of the conjugative plasmid from the donor to the recipient followed by the retrotransfer of the mobilizable plasmid to the donor. This successive model was established for gram-negative bacteria but was lacking experimental data from the gram-positive counterparts. In the present work, the mobilization and retromobilization abilities of the conjugative plasmid pXO16 from Bacillus thuringiensis subsp. israelensis were studied using the mobilizable plasmids pUB110 and pE194 and the "nonmobilizable" element pC194 lacking the mob and oriT features (all from Staphylococcus aureus). Experimental data suggested a successive model, since different retromobilization frequencies were observed between the small plasmids. More importantly, retromobilization was shown to be delayed by 50 and 150 min for pUB110 and pE194, respectively, compared to pXO16 conjugation. Natural liquid foods (cow milk, soy milk, and rice milk) were used to evaluate the putative ecological impact of these transfers. In cow and soy milk, conjugation, mobilization, and retromobilization were shown to occur at frequencies of 8.0 ؋ 10 ؊1 , 1.0 ؋ 10 ؊2 , and 1.2 ؋ 10 ؊4 transconjugants per recipient, respectively. These data are comparable to those obtained with LB medium and about 10-fold lower than in the case of rice milk. Taken together, these results emphasize the potential role of plasmid capture played by B. thuringiensis in natural environments.

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Occurrence of Natural Bacillus thuringiensis Contaminants and Residues of Bacillus thuringiensis -Based Insecticides on Fresh Fruits and Vegetables

Cited by 71 publications

References 28 publications

Apoptosis restores cellular density by eliminating a physiologically or genetically induced excess of enterocytes in the Drosophila midgut

Apoptosis restores cellular density by eliminating a physiologically or genetically induced excess of enterocytes in the Drosophila midgut

A quadruple-enterotoxin-deficient mutant of Bacillus thuringiensis remains insecticidal

Plasmid Capture by the Bacillus thuringiensis Conjugative Plasmid pXO16

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