About: Bacillus thuringiensis is a(n) research topic. Over the lifetime, 9679 publication(s) have been published within this topic receiving 263032 citation(s).
Papers published on a yearly basis
Abstract: A classification for crystal protein genes of Bacillus thuringiensis is presented. Criteria used are the insecticidal spectra and the amino acid sequences of the encoded proteins. Fourteen genes are distinguished, encoding proteins active against either Lepidoptera (cryI), Lepidoptera and Diptera (cryII), Coleoptera (cryIII), or Diptera (cryIV). One gene, cytA, encodes a general cytolytic protein and shows no structural similarities with the other genes. Toxicity studies with single purified proteins demonstrated that every described crystal protein is characterized by a highly specific, and sometimes very restricted, insect host spectrum. Comparison of the deduced amino acid sequences reveals sequence elements which are conserved for Cry proteins. The expression of crystal protein genes is affected by a number of factors. Recently, two distinct sigma subunits regulating transcription during different stages of sporulation have been identified, as well as a protein regulating the expression of a crystal protein at a posttranslational level. Studies on the biochemical mechanisms of toxicity suggest that B. thuringiensis crystal proteins induce the formation of pores in membranes of susceptible cells. In vitro binding studies with radiolabeled toxins demonstrated a strong correlation between the specificity of B. thuringiensis toxins and the interaction with specific binding sites on the insect midgut epithelium. The expression of B. thuringiensis crystal proteins in plant-associated microorganisms and in transgenic plants has been reported. These approaches are potentially powerful strategies for the protection of agriculturally important crops against insect damage. Images
TL;DR: It is demonstrated that ingestion of double-stranded (ds)RNAs supplied in an artificial diet triggers RNA interference in several coleopteran species, most notably the western corn rootworm Diabrotica virgifera virgifiera LeConte, suggesting that the RNAi pathway can be exploited to control insect pests via in planta expression of a dsRNA.
Abstract: Commercial biotechnology solutions for controlling lepidopteran and coleopteran insect pests on crops depend on the expression of Bacillus thuringiensis insecticidal proteins1,2, most of which permeabilize the membranes of gut epithelial cells of susceptible insects3 However, insect control strategies involving a different mode of action would be valuable for managing the emergence of insect resistance Toward this end, we demonstrate that ingestion of double-stranded (ds)RNAs supplied in an artificial diet triggers RNA interference in several coleopteran species, most notably the western corn rootworm (WCR) Diabrotica virgifera virgifera LeConte This may result in larval stunting and mortality Transgenic corn plants engineered to express WCR dsRNAs show a significant reduction in WCR feeding damage in a growth chamber assay, suggesting that the RNAi pathway can be exploited to control insect pests via in planta expression of a dsRNA
TL;DR: In a laboratory assay, it is found that larvae of the monarch butterfly, Danaus plexippus, reared on milkweed leaves dusted with pollen from Bt corn, ate less, grew more slowly and suffered higher mortality than larvae rearing on leaves dusting with untransformed corn pollen or on leaves without pollen.
Abstract: Although plants transformed with genetic material from the bacterium Bacillus thuringiensis (Bt ) are generally thought to have negligible impact on non-target organisms1, Bt corn plants might represent a risk because most hybrids express the Bt toxin in pollen2, and corn pollen is dispersed over at least 60 metres by wind3. Corn pollen is deposited on other plants near corn fields and can be ingested by the non-target organisms that consume these plants. In a laboratory assay we found that larvae of the monarch butterfly, Danaus plexippus, reared on milkweed leaves dusted with pollen from Bt corn, ate less, grew more slowly and suffered higher mortality than larvae reared on leaves dusted with untransformed corn pollen or on leaves without pollen.
TL;DR: Recent evidence suggests that Cyt synergize or overcome resistance to mosquitocidal-Cry proteins by functioning as a Cry-membrane bound receptor, and compares them to the mode of action of other bacterial PFT.
Abstract: Bacillus thuringiensis Cry and Cyt protein families are a diverse group of proteins with activity against insects of different orders - Lepidoptera, Coleoptera, Diptera and also against other invertebrates such as nematodes. Their primary action is to lyse midgut epithelial cells by inserting into the target membrane and forming pores. Among this group of proteins, members of the 3-Domain Cry family are used worldwide for insect control, and their mode of action has been characterized in some detail. Phylogenetic analyses established that the diversity of the 3-Domain Cry family evolved by the independent evolution of the three domains and by swapping of domain III among toxins. Like other pore-forming toxins (PFT) that affect mammals, Cry toxins interact with specific receptors located on the host cell surface and are activated by host proteases following receptor binding resulting in the formation of a pre-pore oligomeric structure that is insertion competent. In contrast, Cyt toxins directly interact with membrane lipids and insert into the membrane. Recent evidence suggests that Cyt synergize or overcome resistance to mosquitocidal-Cry proteins by functioning as a Cry-membrane bound receptor. In this review we summarize recent findings on the mode of action of Cry and Cyt toxins, and compare them to the mode of action of other bacterial PFT. Also, we discuss their use in the control of agricultural insect pests and insect vectors of human diseases.
TL;DR: It is shown by multilocus enzyme electrophoresis and by sequence analysis of nine chromosomal genes that B. anthracis should be considered a lineage of B. cereus and this determination is not only a formal matter of taxonomy but may also have consequences with respect to virulence and the potential of horizontal gene transfer within the B. Cereus group.
Abstract: Bacillus anthracis, Bacillus cereus, and Bacillus thuringiensis are members of the Bacillus cereus group of bacteria, demonstrating widely different phenotypes and pathological effects. B. anthracis causes the acute fatal disease anthrax and is a potential biological weapon due to its high toxicity. B. thuringiensis produces intracellular protein crystals toxic to a wide number of insect larvae and is the most commonly used biological pesticide worldwide. B. cereus is a probably ubiquitous soil bacterium and an opportunistic pathogen that is a common cause of food poisoning. In contrast to the differences in phenotypes, we show by multilocus enzyme electrophoresis and by sequence analysis of nine chromosomal genes that B. anthracis should be considered a lineage of B. cereus. This determination is not only a formal matter of taxonomy but may also have consequences with respect to virulence and the potential of horizontal gene transfer within the B. cereus group.