Assignment of the δ‐endotoxin gene of <i>Bacillus thuringiensis</i> var. <i>israelensis</i> to a specific plasmid by curing analysis

Ward, E.S.; Ellar, D.J.

doi:10.1016/0014-5793(83)80673-5

Cited by 74 publications

(39 citation statements)

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“…The protein is solubilized at the alkaline pHs that occur in the intestines of susceptible insect larvae and is then cleaved by proteases into peptides which produce the toxic effects (29). Crystal formation is not a stable characteristic (6,30). Synthesis of the paracrystalline protoxin is controlled by large plasmids (11,12,30), the maintenance of which is sensitive to frequency of transfer (6) and incubation conditions, such as temperature (30).…”

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“…Crystal formation is not a stable characteristic (6,30). Synthesis of the paracrystalline protoxin is controlled by large plasmids (11,12,30), the maintenance of which is sensitive to frequency of transfer (6) and incubation conditions, such as temperature (30). Interestingly, to some researchers, strains of B. thurine'ensis are virtually indistinguishable phenotypically from Bacillus cereus except for crystal formation (5, 13, 26), but other workers have observed distinct differences between the two taxa (8, 15).…”

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DNA Relatedness among Bacillus thuringiensis Serovars

Nakamura

1994

International Journal of Systematic Bacteriology

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The genetic relationships of Bacillus cereus and of the Bacillus thuringiensis serovars were assessed from measurements of DNA reassociation. A study of 8 to 10 strains each of 13 of the most commonly encountered serovars revealed that the levels of intragroup DNA relatedness for most serovars ranged from 90 to 100%. In contrast, B. thuringiensis serovars canadensis and kenyae consisted of two DNA relatedness groups, each of which exhibited levels of intragroup relatedness of 80% or higher and levels of intergroup relatedness of 60 to 70%. Analyses of DNA relatedness performed with all of the serovars revealed that the taxa were segregated into 11 phena differentiated from each other at about the 65% level; within each phenon the level of relatedness was 80% or higher. Three phena contained strains belonging to more than one serovar; B. thuringiensis serovars alesti and dendrolimus clustered in phenon 1, serovars aizawai, kurstaki, galleriae, and morrisoni clustered in phenon 7, and serovar darmstadiensis and some strains of serovar kenyae clustered in phenon 11.The levels of DNA relatedness between B. cereus and B. thuringiensis strains ranged between 65 and 70%. My results suggest that many of the B. thuringiensis serovars are genetically distinct but closely related.Bacillus thuringiensis was first isolated by Ishiwata (17) in 1901 from diseased silkworms, the larvae of the moth Bombyx mori (L.). A subsequent isolation was made by Berliner (4) in 1911 from diseased larvae of the Mediterranean flour moth, Anagasta kuehniella (Zeller). Discovery of the biocidal activity on the larvae of many lepidopterids suggested that B. thuringiensis could be used as a biological control agent for protection of crops and forests from insects.A striking morphological and taxonomically distinguishing characteristic of B. thuringiensis is the formation of parasporal crystals. These parasporal bodies consist of crystallized protein which is responsible for the insecticidal activity of the organism (1, 16). The protein is solubilized at the alkaline pHs that occur in the intestines of susceptible insect larvae and is then cleaved by proteases into peptides which produce the toxic effects (29). Crystal formation is not a stable characteristic (6,30). Synthesis of the paracrystalline protoxin is controlled by large plasmids (11,12,30), the maintenance of which is sensitive to frequency of transfer (6) and incubation conditions, such as temperature (30). Interestingly, to some researchers, strains of B. thurine'ensis are virtually indistinguishable phenotypically from Bacillus cereus except for crystal formation (5, 13, 26), but other workers have observed distinct differences between the two taxa (8, 15).de Barjac and Bonnefoi (7) noted that B. thuringz*ensis strains could be divided into 24 serovars on the basis of the immunological reactions of the flagellum antigen. Numerical analyses of phenotypic characteristics failed to differentiate the serovars from each other and B. cereus from B. thuringiensis (3). Opinions regarding the...

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DNA Relatedness among Bacillus thuringiensis Serovars

Nakamura

1994

International Journal of Systematic Bacteriology

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“…This subspecies has been reported to contain up to 10 plasmids (8,21). Two of the small plasmids, pTX14-1 and pTX14-3, have been cloned and characterized (3,6,30), a 75-MDa plasmid has been shown to encode the toxin genes (14,21,39,45), and the transfer functions have been ascribed to a 135-MDa plasmid (21) (presumedly the same as pXO16 [36]). …”

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Mobilization of small plasmids in Bacillus thuringiensis subsp. israelensis is accompanied by specific aggregation

1993

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Mobilizations of pBC16 and pAND006, containing the replicon of the Bacillus thuringiensis subsp. israelensis plasmid pTX14-3, between strains of B. thuringiensis subsp. israelensis were examined. Transconjugants appeared after a few minutes and reached a maximum frequency after approximately 2 h. Plasmid pBC16 was mobilized at a frequency approximately 200 times that of pAND006. However, pAND006 was consistently transferred, suggesting that the replicon of pTX14-3 is sufficient to sustain mobilization in B. thuringiensis subsp. israelensis. A specific protease-sensitive coaggregation between strains of B. thuringiensis subsp. israelensis was found to be unambiguously correlated with plasmid transfer. Two aggregation phenotypes, Agr+ and Agr-, were identified in this subspecies. Aggregation disappeared when the optical density of the mating mixture at 600 nm exceeded approximately 1, and it did not reappear upon dilution. Aggregation was shown to involve interactions of cells with opposite aggregation phenotypes, and evidence of a proteinaceous molecule on the surface of the Agr-that is cells involved in aggregation formation is presented. Matings and selection for the presence of two antibiotic resistance plasmids followed by identification of the host cell revealed that mobilization was unidirectional, from the Agr+ cell to the Agr-cell. The aggregation phenotype was found to be transferred with high frequency ("100%) in broth matings, and the appearance of Agr-isolates from Agr+ strains suggested that the loci involved in aggregation formation are located on a plasmid. No excreted aggregation-inducing signals were detected in the supernatant or culture filtrate of either the donor, the recipient, or the mating mixture.Conjugation, the direct transfer of genes from one bacterial cell to another, is often mediated by large conjugative plasmids. These large plasmids are transferred at high frequency, and occasionally chromosomal genes and smaller nonconjugative plasmids are cotransferred by the transfer apparatus of the conjugative plasmids. In gram-negative bacteria many small nonconjugative plasmids can be transferred (mobilized) if an additional self-transmissible plasmid is present in the host (13, 46, 47). Recent reports have described similar mobilizations of small plasmids in gram-positive bacteria (2,5,26,34,40). The first studied and best understood of the conjugative plasmids is the F plasmid, which can replicate in Escherichia coli and certain closely related enteric bacteria. The mechanism of F plasmid-mediated conjugation involves physical contact of the cells and transfer of plasmid DNA brought about by the sex pilus (23). Studies of the gram-positive bacterium Enterococcus (formerly Streptococcus) faecalis suggest a mechanism quite different from that in the better-studied gram-negative systems. Pili do not play any role in conjugation between strains of this organism, but pheromone-induced aggregation between cells has been shown to be a major characteristic (11,15).

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“…Previous studies have discovered that most of the δ-endotoxin genes of B. thuringiensis are positioned on the megaplasmids (Gonzalez et al, 1982;Ward and Ellar, 1983) and/or occasionally, in the chromosome (Kronstad et al, 1983;Lereclus et al, 1993). Plasmid patterns of B. thuringiensis can be divided into two groups; the small plasmids and the megaplasmids.…”

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confidence: 99%