agricultural microbiology : its scope and importance

1. P G DEPARTMENT OF ZOOLOGY
MINOR 2
SEM4
TOPIC: AN INTRODUCTION TO AGRICULTURAL
MICROBIOLOGY
SUBMITTED TO: DR. RUCHIKA
SUBMITTED BY: VAISHALI SHARMA
R.NO:01

3. • Although agricultural microbiology is further classified into
soil microbiology and plant pathology but the above 2
branches are better known as separate sciences.
• During the last decade major findings were made i.e.,
A)soluble phosphate fertilisers could be used for crop
improvement
B)soil fertility could be maintained by the use of organic
fertilisers
C)the plant diseases could be controlled by using
microorganisms.
• Several bio fertilisers have been commercialised for
increasing crop fertility many bacteria and fungi have been
discovered for the use in controlling various plant diseases

4. • it is now obvious to learn that use of microbial inoculant will be
more helpful in solving present and future problems of men.
• What are microbial inoculants?
• A formulation that contains one or more beneficial microbial
strains in an easy to use and economical carrier material,
organic, inorganic or synthesised from defined molecules.
• The desired effects of the inoculants on plant growth include
1. nitrogen fixation
2. bio control of many soil borne diseases
3. the enhancement of mineral uptake weathering of soil minerals
and
4. nutritional or hormonal effects.

5. • Microbial consortium or mixed inoculants
• .it is a combination of microbes that interact with other
synergistic microbes.
• all of them provide
1. nutrients
2. remove inhibitory products
3. stimulate each other through physical and biochemical
activities.
• A mixture of Azospirillum and Cellulomonas In which the former
provides nitrogen to the Cellumonas Which degrades cellulose
into glucose. this glucose acts as carbon source to Azospirillum.

9. • Main contributions of agricultural microbiology include
BIOFERTILIZERS and BIOPESTICIDES
• Types of BIOFERTILIZERS:
1. Bacterial bio fertilizer
2. Algal bio fertilizer
3. Endophytic nitrogen fixers
4. Biofertilizers aiding phosphorus nutrition
• BIOPESTICIDES include:
1. Microbial insecticides
2. Bacterial insecticides
3. Viral insecticides
Applications of agricultural microbiology

10. Biofertilizers:
• Biofertilisers are the formulations of living microbes which are able to
fix atmospheric nitrogen in the available form for plants either by
living freely in the soil or associated symbiotically with plants.
• In India the production of bio fertilisers on commercial scale was
started only during the late 1960s when the yellow seeded soya bean
was introduced for the first time
• Biofertilizers are being recommended in place of chemical fertilisers
because chemical fertilisers
1. pose health hazards
2. pollution problems and
3. are expensive

13. This Photo by Unknown Author is licensed under CC BY

17. 3) Algal biofertilizer
• Azola Anabaena complex
• It contributes 40 to 60 kilogramme nitrogen per hectare per rice crop
• The use of neem Coupled with the inoculation of Azolla greatly increased the nitrogen
utilisation efficiency in rice
• Cyanobacteria help to
1. add organic matter
2. secrete growth promoting substances like auxins & vitamins
3. mobilise insoluble phosphate
4. and improved physical and chemical nature of the soil
5. Alkalization has been shown to ameliorate the saline alkali soils
6. help in the formation of soil aggregates
7. reduce soil compaction

18. Anabeana

19. 4)Endophytic nitrogen fixers
• The term endophyte refers to microbes that
colonise root interior of plant
• Endophytes have the ability to colonise the entire
plant interior and thus their potential to fix
nitrogen can be expressed maximally.

20. 5)Biofertilizers aiding phosphorus nutrition
• Many microbes solubilise phosphorus and thus make it
available for plant growth
• Bacteria such as Aspergillus penicillum solubilise unavailable
form of phosphorus to available form
• Vesicular arbuscular mycorhhiza result fungi call a nice
roots of several crop plants nick
• nearly 25 to 30% off phosphate fertiliser can be saved
through inoculation with efficient V AM fungi as reported
by bagyaraj(1992).

21. ADVANTAGES OF BIO FERTILIZERS:
1. Biofertilizers act as supplements to chemical fertilisers.
2. Biofertilizers are cost-friendly and can aid to decrease
consumption of such fertilisers.
3. Microbes in biofertilizers provide atmospheric nitrogen directly to
plants.
4. They aid in solubilisation and mineralisation of other plant
nutrients like phosphates.
5. Better synthesis and availability of hormones, vitamins, auxins
and other growth-promoting substances improves plant growth.

22. 6. On an average crop yield elevates by 10–20 percent
by their use.
7. They help in the multiplication and survival of
beneficial micro-organisms in the root region
(rhizospheric bacteria).
8. They control and inhibit pathogenic soil bacteria.
9. They enhance soil texture by increasing amount of
humus and maintain soil fertility.
10. Eco-friendly in nature and pollution free

23. DISADVANTAGES OF BIO FERTILIZERS
1. Biofertilizers are supplement to chemical fertilizers but not
substitute to it.
2. Biofertilizers only result in 20 to 30 percent increase in crop
production. They do not cause marked increase in productivity like
chemical fertilizer.
3. Specific fertilizers are required for specific crops. This is more
applicable to symbiotic micro-organisms. If non-specific Rhizobium
is used as fertiliser, then it will not lead to root nodulation and
increase in crop production.
4. During the production of microbial fertiliser, strict aseptic
precaution is needed. Contamination is a common issue during
microbial mass production.

24. 5. If exposed for long time in sunlight, microbes get killed as
they are light-sensitive.
6. Microbial fertilizer must be used within six months after
production when stored at room temperature and within
two years if stored at chilling temperature.
7. Efficiency of microbial fertilizer depends on soil character,
such as, moisture content, pH, temperature, organic
matter and types of micro-organisms present. When
these factors are unfavourable microbial fertilizer may not
be effective in enhancing the soil fertility

26. Bio pesticide can be categorized
into:
1. MICROBIAL HERBICIDE
2. VIRAL INECTICIDE
3. FUNGAL INSECTICIDE
4. MICROBIAL NEMATICIDE
5. BACTERIAL INSECTICIDE

27. 1)Microbial herbicides
• The use of endemic or exotic plant pathogens to kill weeds is known as microbial
herbicides.
• It is an alternative to chemical weedicide
• MAJOR EXAMPLES:
1. Puccinia chondrillina is a plant pathogen used to control Chondrilla juncea or
skeleton weed in Australia,
2. Cercosporella riparia controls the growth of Ageratina riparia in Hawaii,
3. Phragmidium violaceum was reported for its activity against wild blackberry (Rubus
spp)
4. Control of water hyacinth by Cercospora rodmanii,
5. The effectiveness of Colletotrichum gloesosporioides against Aeschynomene virginica
etc.

28. skeletonweed rust (Puccinia chondrillina
) on rush skeletonweed

29. 2)

32. 3)

33. Hirsutella fungus

35. 4)BACTERIAL PESTICIDE:
• There are certain bacteria which are pathogenic to
kill insect pests an adult petitions and kill these
wide range of parasitic organisms
I. Pseudomonas as Bacterial Insecticide
II. Bacillus as Bacterial Insecticide
a) Bacillus thuringiensis
b) Other Bacillus species

36. I.Pseudomonas as Bacterial Insecticide
• Along with plant growth promotion, several Pseudomonas
species are reported to have pathogenicity against several
insects.
• Pseudomonas aeruginosa is one of the species which is mostly
reported as a bacterial insecticide.
• P. taiwanensis was reported for its insecticidal activity against
agricultural pests such as Plutella xylostella, Spodoptera exigua,
S. litura, etc.
• These bacteria mostly carry toxin complex genes that have
specificity towards insects.
• P. fluorescence involves bacterial antagonists to control fungal
pathogens.
• P. cepacia was also reported for its activity towards suppression
of plant-pathogen by secretion of siderophores.

37. Pseudomonas aeruginosa

39. II. Bacillus as Bacterial Insecticide
• a) Bacillus thuringiensis
• B. thuringiensis (Bt) is widely used bacilli which can control insects
such as moths, beetle, flies, aphids, butterflies, and even some
pathogenic fungi like Pythium ultimum.
• The mechanism of Bt to control the insects is depending on its toxins.
The endotoxin is a crystallized protein that is soluble in alkaline
conditions.
• The pH in the gut of an insect is mostly alkaline and as it ingested the
toxin, the toxin easily dissolves in the midgut region.
• Then proteases come into action by digesting the toxin which leads to
the production of small active fragments.
• These active fragments then bind to the gut epithelial membrane and
create pores which leads to disturbance in osmotic equilibrium.
• This results in the death of the insects.
• Several agricultural plants were genetically modified with the gene
responsible for toxin production in Bt., such plants are Bt. Brinjal, Bt.
Tomato etc

43. • b) Other Bacillus species
• B. thuringiensis is one of the bacillus species which is used
widely to control insects.
• However, there are other Bacillus species such as B.
papilliae and B. lentimorbus which play an important role in
controlling insects such as Japanese beetle.
• LEARN MORE ABOUT Bt:
• Bacillus thuringiensis (Bt) – YouTube
• Bt Cotton simplified tricks/action of Bt toxin for all biology
exams. - YouTube

45. Drawbacks of Bacterial Insecticides
• Many bacterial insecticides are specific for a species of pest.
In many cases, these insecticides kill only one type of insects
and the other type of insects survive and continue to cause
damage to the crop.
• In the case of genetically modified plants such as Bt. the
hypersensitive reaction occurred to the animals and humans
consumed the plant.
• Environmental factors such as heat, desiccation, etc. can
affect the viability of the bacteria. Therefore, it is difficult to
maintain proper application procedures.
• Due to the same reason, proper preservation and storage
are required for some bacterial insecticides.