Insect Midgut Endotoxins

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Questions and Answers

What is the optimal temperature for the active feeding of insects and ticks mentioned in the passage?

  • 32-35° C
  • 5-8° C
  • 10-15° C
  • 17-18° C (correct)

When does the death of phytophages typically occur after treatment with BT drugs?

  • 1-2 days after treatment
  • 3-5 days after treatment (correct)
  • 10-12 days after treatment
  • 6-8 days after treatment

What is the waiting period after using BT-based drugs in organic farming?

  • 5 days (correct)
  • 3 days
  • 7 days
  • 10 days

What is the primary action of BT-based drugs on phytophages?

<p>Lethal action (B)</p> Signup and view all the answers

What is the main advantage of transgenic plants based on Bacillus thuringiensis compared to the technology of spraying with bacterial preparations?

<p>Continuous production of toxins in every cell of the plant (C)</p> Signup and view all the answers

What does the cultivation of BT plants contribute to, according to world experience?

<p>Expanded range of hosts for toxins (C)</p> Signup and view all the answers

What does Bacillus thuringiensis synthesize that is promising for biocontrol?

<p>An extraordinary variety of insecticidal proteins (B)</p> Signup and view all the answers

What is the focus of plant protection in recent decades?

<p>Biologization and ecologization (C)</p> Signup and view all the answers

What percentage of the total number of permitted drugs are biological insecticides and acaricides?

<p>6.3-6.7% (B)</p> Signup and view all the answers

What are examples of entomopathogenic preparations mentioned in the text?

<p>Bacteria, viruses, and fungi (C)</p> Signup and view all the answers

What is the share of entomopathogenic bacteria, viruses, fungi, nematodes, microbial toxins, and regulators of growth in terms of active substances for future preparations?

<p>About 20% (D)</p> Signup and view all the answers

What is the primary focus of microbiological control in ecosystems?

<p>Microbiological control of the number of harmful organisms (A)</p> Signup and view all the answers

How has the scientific intensity of crop production changed in recent years?

<p>Increased moderately (C)</p> Signup and view all the answers

What is the role of BT in insect control?

<p>Increasing water permeability and rupturing intestinal cell membranes (C)</p> Signup and view all the answers

What is the specific designation for the genes encoding insecticidal delta-endotoxin proteins?

<p>cry (B)</p> Signup and view all the answers

Which type of BT cultures have a wider spectrum of entomocidal action and are promising for drug production?

<p>Exotoxinogenic (D)</p> Signup and view all the answers

What makes the safety of BT and its metabolites widely accepted in plant protection practice?

<p>Toxicological studies (C)</p> Signup and view all the answers

Which group of entomofauna is crystalline endotoxin toxic to?

<p>A narrow group due to low pH requirement for mammalian protein digestion (C)</p> Signup and view all the answers

What is the mechanism by which some BT subspecies inhibit DNA-dependent RNA polymerase?

<p>Thermally stable exotoxins (A)</p> Signup and view all the answers

Which entomopathogen is the most commonly used in the global biopesticide market?

<p>Bacterial insecticides (Bacillus thuringiensis Berliner) (C)</p> Signup and view all the answers

When was the first commercial BT product introduced in the USA?

<p>1958 (A)</p> Signup and view all the answers

What is the mechanism of action of BT determined by?

<p>Parasporal toxins (Cry and Cyt) or soluble Vip and Sip toxins (A)</p> Signup and view all the answers

What does crystalline delta-endotoxin have a thermolabile protein structure and is insoluble in water but soluble in alkaline solutions?

<p>Bacillus thuringiensis Berliner (BT) (C)</p> Signup and view all the answers

Where was the first bacterial insecticide, Entobacterin, produced?

<p>Soviet Union (D)</p> Signup and view all the answers

Which complex preparation is effective against leaf-eating pests and some plant diseases and has been created and used in Belarus?

<p>Xantrel (C)</p> Signup and view all the answers

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Study Notes

  • Entomopathogens, natural elements found in biocenosis, serve as basis for biological preparations against plant pests.
  • Bacterial, viral, fungal and other drugs are distinguished based on the nature of entomopathogens.
  • Bacterial insecticides and acaricides are derived from entomopathogenic bacilli, with Bacillus thuringiensis Berliner (BT) being the most commonly used.
  • BT is a soil, gram-positive, spore-forming bacterium with approximately 90-95% share in the global biopesticide market.
  • Over 70 BT varieties effective against phytophages have been identified, with high selectivity, safety for useful entomofauna, fish, and warm-blooded animals.
  • First bacterial insecticide, Entobacterin, was produced in the Soviet Union in the early 1950s.
  • First commercial BT products were introduced in France in 1938 and the USA in 1958.
  • Bactospeine, Foray, Biobit, DiPel and others are well-known commercial products based on BT.
  • Complex preparation Xantrel, effective against leaf-eating pests and some plant diseases, has been created and used in Belarus.
  • BT is found in various types of soils, on plant surfaces, in leaf litter, and in insect bodies.
  • BT isolates are found on different continents and in most countries worldwide.
  • BT-based preparations are safe for humans and warm-blooded animals, non-target organisms, and the environment.
  • Mechanism of action of BT is determined by parasporal toxins (Cry and Cyt) or soluble Vip and Sip toxins.
  • Numerous non-toxic BT virulence factors, such as metalloproteases, chitinases, aminopolyol antibiotics, and fragments imitating nucleotides, affect insects differently.
  • Bacteria cause diseases, leading to septicemia and the release of crystalline delta-endotoxin, which degrades under intestinal enzymes to release a true toxin.
  • Crystalline delta-endotoxin has a thermolabile protein structure and varies in shape, being insoluble in water but soluble in alkaline solutions.
  • Endotoxin causes pathological processes, including structural disorganization of the intestinal epithelium, permitting the bacterium's participation in the septicemia.

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