Introduction to Bioactive Compounds and Bacterial Pesticdes

Biopesticides can be classified into these classes:Microbial pesticides which consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce). Entomopathogenic nematodes are also often classed as microbial pesticides, even though they are multi-cellular. Bio-derived chemicals. Four groups are in commercial use: pyrethrum, rotenone, neem oil, and various essential oils are naturally occurring substances that control (or monitor in the case of pheromones) pests and microbial diseases. Plant-incorporated protectants (PIPs) have genetic material from other species incorporated into their genetic material (i.e. GM crops). Their use is controversial, especially in many European countries. RNAi pesticides, some of which are topical and some of which are absorbed by the crop. Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. Microbial pesticides can control many different kinds of pests, although each separate active ingredient is relatively specific for its target pest. Bacillus thuringiensis, a bacterial disease of Lepidoptera, Coleoptera and Diptera, is a well-known insecticide example. The toxin from B. thuringiensis (Bt toxin) has been incorporated directly into plants through the use of genetic engineering. The use of Bt Toxin is particularly controversial. Its manufacturers claim it has little effect on other organisms, and is more environmentally friendly than synthetic pesticides. However, at least one scientific study has suggested that it may lead to slight histopathological changes on the liver and kidneys of mammals with Bt toxin in their diet. Other microbial control agents include products based on: entomopathogenic fungi (e.g.Beauveria bassiana, Paecilomyces fumosoroseus, Lecanicillium spp., Metarhizium spp.), plant disease control agents: include Trichoderma spp. and Ampelomyces quisqualis (a hyper-parasite of grape powdery mildew); Bacillus subtilis is also used to control plant pathogens. beneficial nematodes attacking insect (e.g. Steinernema feltiae) or slug (e.g. Phasmarhabditis hermaphrodita) pests entomopathogenic viruses (e.g.. Cydia pomonella granulovirus). weeds and rodents have also been controlled with microbial agents. Various naturally occurring materials, including fungal and plant extracts, have been described as biopesticides. Products in this category include: Insect pheromones and other semiochemicals Fermentation products such as Spinosad (a macro-cyclic lactone) Chitosan: a plant in the presence of this product will naturally induce systemic resistance (ISR) to allow the plant to defend itself against disease, pathogens and pests. Biopesticides may include natural plant-derived products, which include alkaloids, terpenoids, phenolics and other secondary chemicals. Certain vegetable oils such as canola oil are known to have pesticidal properties.

Summary

Biopesticides can be classified into these classes:Microbial pesticides which consist of bacteria, entomopathogenic fungi or viruses (and sometimes includes the metabolites that bacteria or fungi produce). Entomopathogenic nematodes are also often classed as microbial pesticides, even though they are multi-cellular. Bio-derived chemicals. Four groups are in commercial use: pyrethrum, rotenone, neem oil, and various essential oils are naturally occurring substances that control (or monitor in the case of pheromones) pests and microbial diseases. Plant-incorporated protectants (PIPs) have genetic material from other species incorporated into their genetic material (i.e. GM crops). Their use is controversial, especially in many European countries. RNAi pesticides, some of which are topical and some of which are absorbed by the crop. Microbial pesticides consist of a microorganism (e.g., a bacterium, fungus, virus or protozoan) as the active ingredient. Microbial pesticides can control many different kinds of pests, although each separate active ingredient is relatively specific for its target pest. Bacillus thuringiensis, a bacterial disease of Lepidoptera, Coleoptera and Diptera, is a well-known insecticide example. The toxin from B. thuringiensis (Bt toxin) has been incorporated directly into plants through the use of genetic engineering. The use of Bt Toxin is particularly controversial. Its manufacturers claim it has little effect on other organisms, and is more environmentally friendly than synthetic pesticides. However, at least one scientific study has suggested that it may lead to slight histopathological changes on the liver and kidneys of mammals with Bt toxin in their diet. Other microbial control agents include products based on: entomopathogenic fungi (e.g.Beauveria bassiana, Paecilomyces fumosoroseus, Lecanicillium spp., Metarhizium spp.), plant disease control agents: include Trichoderma spp. and Ampelomyces quisqualis (a hyper-parasite of grape powdery mildew); Bacillus subtilis is also used to control plant pathogens. beneficial nematodes attacking insect (e.g. Steinernema feltiae) or slug (e.g. Phasmarhabditis hermaphrodita) pests entomopathogenic viruses (e.g.. Cydia pomonella granulovirus). weeds and rodents have also been controlled with microbial agents. Various naturally occurring materials, including fungal and plant extracts, have been described as biopesticides. Products in this category include: Insect pheromones and other semiochemicals Fermentation products such as Spinosad (a macro-cyclic lactone) Chitosan: a plant in the presence of this product will naturally induce systemic resistance (ISR) to allow the plant to defend itself against disease, pathogens and pests. Biopesticides may include natural plant-derived products, which include alkaloids, terpenoids, phenolics and other secondary chemicals. Certain vegetable oils such as canola oil are known to have pesticidal properties.

Things to Remember

Biopesticides have good point and negative points also. And these things are necessary to keep in mind.

Advantages

  • No harmful residues produced, i.e. biodegradable.
  • Can be cheaper than chemical pesticides when locally produced.
  • Can be more effective than synthetic pesticides in the long-term

Disadvantages

    • High specificity: which may require an exact identification of the pest/pathogen and the use of multiple products to be used; although this can also be an advantage in that the biopesticide is less likely to harm species other than the target
    • Often slow speed of action (thus making them unsuitable if a pest outbreak is an immediate threat to a crop)
    • Often variable efficacy due to the influences of various biotic and abiotic factors (since some biopesticides are living organisms, which bring about pest/pathogen control by multiplying within or nearby the target pest/pathogen)
    • Living organisms evolve and increase their resistance to biological, chemical, physical or any other form of control. If the target population is not exterminated or rendered incapable of reproduction, the surviving population can acquire a tolerance of whatever pressures are brought to bear, resulting in an evolutionary arms race.
    • Unintended consequences: Studies have found broad spectrum biopesticides have lethal and nonlethal risks
 

MCQs

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Subjective Questions

Q1:

Which period is known as the period of a golden age?


Type: Very_short Difficulty: Easy

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Answer: <p>Lichchhavi period is known as the period of a golden age.</p>

Q2:

Why is the soil of Kathmandu valley is fertile?


Type: Short Difficulty: Easy

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Answer: <p>The soil of Kathmandu&nbsp;valley is fertile because all the fertile soil, gravel is deposited in the &nbsp;valley which is brought by the several rivers around the hills which flow into the valley.</p>

Q3:

Describe the dynasties that ruled over the Kathmandu valley?


Type: Long Difficulty: Easy

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Answer: <p>There are various dynasties that ruled over Kathmandu valley. Some of them are Kirant&nbsp;dynasty, Mahispal dynasty, Gopal dynasty and Malla dynasty. The first dynasty that ruled over Kathmandu valley is Gopal&nbsp;dynasty which ruled about 521 years. Then after Mahispal dynasty came into the power. Mahispal dynasty ruled over the valley for about 161 years. After Mahispal dynasty, Kirant&nbsp;dynasty ruled over the valley. They ruled for about 1118 years in the valley which was the highest rule over Kathmandu valley in the history of Nepal. After defeating Kirant,&nbsp;Lichchhavi came into the power and after them, Mallas came into the power. After defeating Mallas, King Prithvi Narayan Shah unified the whole nation which is called Nepal. &nbsp;</p>

Q4:

Why is Lichchhavi period known as the Golden age?


Type: Short Difficulty: Easy

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Answer: <p>Lichchhavi period is known as the Golden age because in LIchchhavi period there was the tremendous progress in the field of art, culture and philosophy.</p>

Q5:

In what fields did the Mallas do the progress?


Type: Short Difficulty: Easy

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Answer: <p>Mallas did the progress in all around the development of the country. They did progress in the field of trade, art, architecture, etc. The buildings, palaces, temples, ponds, statues, etc were made in the period of Mallas.</p>

Q6:

Who cut the hill of Chobhar to flow out the water of a lake?


Type: Very_short Difficulty: Easy

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Answer: <p>Manjushree Bodhistwo&nbsp;cut the hill of Chobhar to flow out the water of lake.</p>

Videos

1950s Nepal Documentary by Toni Hagen Part 1 of 2
Ancient Kathmandu
Introduction to Bioactive Compounds and Bacterial Pesticdes

Introduction to Bioactive Compounds and Bacterial Pesticdes

Bioactive compounds are extranutrional constituents.

Biopesticides

Many microorganisms are used in biological control of various pests of agricultural crops. They are used to control insects, fungi and weeds occurringin cultivated plants. Biological control is the process of killing or inhibiting pest of agricultural cropsby using biological agents like microorganisms . microorganisms used in biological control of pest are called biopesticides . Many bacteria, fungi and virus have insecticidal, fungicidal and herbicidal activity and are used in biological control of these pests.

Chemical vs. Microbial pesticides

Chemical pesticides Biopesticides
Spees of action is usually rapid. Speed of action is usually slow.
Killing efficiency is almost 100%. Killing efficiency is usually 90-95%
They usually have broad spectrum of action. They usually have narrow spectrum of action.
It causes many environmental hazards. Environmental hazards are not yet seen.
Product treated with chemical pesticides may be toxic to consumers. Products treated with biopesticides is not usually toxic to consumers.
Resistance by targeted pest is often developed. Resistance by targeted pest is not yet seen.

Advantages of Microbial Biopesticides

  1. They are eco-friendly and causes least contamination or pollution in theenvironment.
  2. They are cheaper than the chemical pesticides.
  3. Cases of resistance are rarely developed.
  4. They preserve helpful insects i.e. they do not destroy non-target insect.
  5. They do not leave residues in the applied field, food products, and plant parts.
  6. Product treated with biopesticides is not usually toxic to consumers.
  7. They focus on management rather than eradication thus maintaining the ecological balance.

Disadvantages

  1. Speed of action is usually slow.
  2. Killing efficiency is not 100% (usually 90-95%).
  3. They usually have narrow spectrum of action.
  4. They have short life.
  5. They have limited field persistance.
  6. They are not readily available in many countries.
  7. They need frequent monitoring.

Conditions for microorganisms to be successful biopesticides

  1. It must be equal to or better than chemical pesticides in stability and performance.
  2. The product must be safe with low mammalian toxicity and have little effect on non-target species.
  3. It should remain stable during storage.
  4. Production process should be cheaper and easier.
  5. Biopesticides should be applicable in field by using conventional technologies.

Some Bacterial, Viral and Fungal pesticides

Bacterial Pesticides

Bacterial pesticides have been used to control plant diseases, nematodes and weeds. Many spore-forming and non spore forming bacteria are known to be effective against wide range of insects and diseases. The bacteria that can be used as biopesticides are:

Bacillus thuringiensis Pseudomonas aeruginosa

Bacillus subtilis Pseudomonas fluorescens

Bacillus pumilus Aerobacter aerogens

Bacillus popilliae

Bacillus lentimobus

1. Bacillus thuringiensis (Bt)

Bacillus thuringiensis is the most well known and widely used bacterial biopesticides. It is commonly referred to asBt.They are aerobic, Gram-positive bacilli found in soil. During spore formation,Bt produces insecticidal proteins (crystal protein) known as delta-endotoxin that kills different types of pest of agricultural and non-agricultural plants.

Btis commercially produced by submerged state of fermentation and is mixed with carriers like charcoal powder. During application in thefield, it is dissolved in water in thenspread on leafs. On leaf. bacteria multiply and produce crystal protein. When aninsect ingests leaf, crystal protein enters into the gut of insect. On alkaline environment found in the midgut of insect, crystal protein is converted into active toxic form. Activated protein binds to the cell of midgut which results in swelling and burst. The process of killing insects from this crystal protein is rather slow and takes about 24-48 hours. Although thedeath of insect occurs slowly, the insect is paralysed and stop feeding on theleaves.Btalso producesβ-exotoxin which is highly effective against housefly. Unfortunately,β-exotoxin has mammalian toxicity.

Bthas several strains each of which produces different types of toxins that can kill different types of insects. Some important sub-species ofBacillus thuringiensisused in the control of different species of insect are given below:

Bacillus thuringiensissub-species

 Trade name Insect control
Bacillus thuringiensis sub- species kurstaki Biobit, Dipel, Thuricide,Javelin Many Lepidopteron including Beetle, cabbage worm, etc.
Bacillus thuringiensis sub-species israelensis Azrobe, Tekar, Bactimos Diaptera like mosquitoes, black flies, fungus gnat larvae, etc.
Bacillus thuringiensis sub-species tenebrionis Trident, Novodor Larvae of leaf beetle, potato beetle, etc.
Bacillus thuringiensis sub-species aizawai Florbac Many Lepidoptera larvae

Application of Bacillus thuringiensis

Crystal protein of Bt is known to be non-toxic to human but toxic only to pest so it is safer to use than chemical pesticides. It kills different types of insects of agricultural and non-agricultural plants. Different sub-species of Bt used in control of different species of insects are given above.

During application in the field, it is dissolved in water and spread on leaves of agricultural crop. To control mosquito larvae, formulation containing the sub-species israelensisstrains are placed into the stagning water of mosquito breeding sites.

2.Bacillus popilliaeandBacillus lentimobus

They are Gram-positive, rod-shaped, spore-forming bacteria found in soil. They are pathogenic to Japanese beetle that attack many trees, shrubs and herbs. They grow inside Japanese beetle and cause milky spore disease. After the beetle eat the bacteria, there body fluids turn milky and they die releasing more of the bacterial spores into the soil. Milky spore disease is specific for Japanese beetle and it won't harm other animals and plants.

3.Bacillus subtilis

It is primarily a bactericide that eliminate the deleterious fast growing bacteria and pathogenic fungi likeFusarium, Aspergillus, Rhizoctina,etc. in rhizopheric soil by colonising and out competing them for nutrients and habitat.

4. Pseudomonas fluorescens

P. fluorescensis a Gram-negative, rod-shaped bacteria. SomeP. fluorescensstrains can be used as biopesticides which protects the roots of some plants species against parasitic fungi such asFusariumas well as some phytophagous nematodes. It crowds out in rhizosphere and control the population of plant pathogen.

Commercial production of Biopesticides

Production of Bacterial

Bacteria and Fungi can grow in non-living cultivation media. They are commercially produced by typicak fermentation process. Bacteria are produced in liquid cultivation media but fungi are usually produced by cultivating them in solid concentration media. It is because most fungi do not produce spores in liquid cultivation media.

At first, cultivation media is prepared by mixing al; essential nutrients. Then media is sterilized by heating. It;s pH is adjusted and cooled. Then cultivation media is placed in production fermentation tank. Then the inoculum of organism is added in the media and is incubated. During incubation, bacteria multiply and increase in number. After incubation, microbial cells are separated from other debris by various techniques like centrifugation, precipitation, filtration, etc. Bacterial cells are then mixed with some stable carriers like charcoal powder and then packed until the application in field. Biopesticides are preserved by storing them in cold environment. In case of fungi. spores are harvested and then mixed with carriers.

Fig. Commercial production of bacterial and fungal pesticides
Fig. Commercial production of bacterial and fungal pesticides

Reference

Atlas, RM and R Bartha. Microbial Ecology:Fundamentals and Applications. The Benjamin Cummins Publication co. Inc., 1998.

Gordis, L. Epidemiology. third edition. 2004.

Maier, RM, IL Pepper and CP Gerba. Environmental Microbiology. Academic press Elsevier Publication, 2006.

park, K. Park's Text Book of social and prevention Medicine. 18th edition. 2008.

Lesson

Bioactive compounds of microorganisms

Subject

Microbiology

Grade

Bachelor of Science

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