Role of Soil Microflora in Agriculture By Rajendra Prasad – Uttaranchal University

Course Learning Outcomes

Table of Content

• Lecture 1: Outlines of Microorganisms

  • Microorganisms are those living creatures that cannot be seen through naked eyes. It can be seen through a microscope only. They are present everywhere i.e., in air, water, soil, any surface, inside the gut of living organisms, etc. They are usually useful organisms and have an important role in the environment. Some of them are harmful to human beings.

• Lecture 2: Microflora of Soil

  • About 10 billion microorganisms inhabit each gram of soil. Microorganisms present in soil: Bacteria, fungi (yeast, mold, soil fungi, Mycorrhiza, mushroom), virus, protozoa, etc.

• Lecture 3: Soil microorganisms on plant

  • Very high diversity of microflora in soil, about 8000 species of bacteria, millions of fungi, About 3000 of algae, About 20,000 protozoa

• Lecture 4: Historical background of Soil Microbiology 

  • Four people were known about fermentative microorganisms and used them for the preparation of wine, crud, etc. Many diseases reported in the story and holy books Archaeological evidence of stromatolite

• Lecture 5: Koch's Postulates

  • Robert Koch provided experimental proof of the germ theory by isolating the cause of anthrax and showing it to be a bacterium. He established the relationship between pathogen and host and give four postulates, popularly known as Koch's Postulates. These postulates are still used today to confirm the pathogenicity of microorganisms.

• Lecture 6: Soil as Natural Habitat of Microorganism 

  • More than 30% of all livings on the Earth use soil as a habitat. About 90% of microorganisms live in soil, some live on top of the soil, others live below the surface. One gram of soil contains billions of microorganisms, Bacteria present everywhere

• Lecture 7: Soil Bacteria 

  • Placed in Kingdom Monera, Single-cell, Prokaryote, Single circular piece of DNA

• Lecture 8: Morphology of Bacteria 

  • Cytoplasmic membrane: It is 5-10 um thick elastic semipermeable layers, which lie beneath the cell wall separating it from the cytoplasm. Act as a semipermeable membrane controlling inflow & outflow of metabolites to & from the protoplasm. Site of numerous enzymes (permease, oxidase, and polymerase) involved in the active transport of selective nutrients

• Lecture 9: Soil Fungi 

  • Fungi are eukaryotic organisms, they neither plants nor animals. They group themselves into fibrous strings called hyphae. The groups of hyphae called mycelium are less than 0.8mm wide is. These may belong to several meters. Fungi are helpful because they have the ability to break down nutrients that other organisms cannot.

• Lecture 10: Soil Actinomycetes

  • The name refers to the ray-like appearance of the organism in the granules (Antinomies, meaning ray fungus), Mode of infection: mostly endogenous & trauma e.g. dental extraction

• Lecture 11: Soil Algae 

  • Prokaryotic Algae: Autotrophic organisms, Single-celled to filamentous blue-green alga or cyanobacteria.

• Lecture 12: Soil Protozoa

  • Types of soil Protozoa: Ciliates, the Largest of the three, move by means of hair-like cilia, eat the other protozoa and bacteria.

• Lecture 13: Soil Viruses

  • Obligate Intracellular Parasites – only demonstrate characteristics of life while “inside” a host cell:  Bacteria, animal, plant. Outside a host cell, inert, no enzyme or other activity. Inside a host cell – viral Nucleic Acid (DNA or RNA) takes over the cell and directs the cell to produce new virus particles (replication)

• Lecture 14: Microbial Interactions in Soil

  • Plant roots form a part of a multitude of organismic interactions within the soil. Due to the release of organic compounds, they attract diversified microbiological populations where fungi and bacteria can form distinct communities. In the rhizosphere, soil microflora can be extremely helpful for the plant in facilitating the supply of water and nutrients (mycorrhiza)

• Lecture 15: Method of Studying Soil Microflora

  • Direct microscopic method: It is useful in examined for numbers of bacterial clumps or somatic cells, direct microscopic clump (DMC) count, the fast method takes less time, could not apply to all samples

• Lecture 16: Agar plate technique

  • A relatively more convenient method of counting microorganisms, routinely used in the laboratory to isolate, or enumerate microorganisms, Total bacteria count (TBC), Standard plate count (SPC).

• Lecture 17: Serial Dilution Method

  • A microorganism that predominates in a mixed culture can be isolated in pure form by a series of dilutions. The inoculum is subjected to serial dilution in a sterilized liquid medium in a large number of tubes each containing 9 ml of liquid medium. In this method mix culture of the sample is prepared in a flask. From the flask a specific amount i.e., 1 ml of inoculums is transferred in liquid medium in tube one and mixed thoroughly.

• Lecture 18: Pour Plate Method

  • This involves the plating of diluted samples mixed with melted agar medium. The main principle is to dilute the inoculum in successive tubes containing normal saline water or buffer by serial dilution method. A quantity of 1 ml of the mixed culture of bacteria from tubes transferred in separate Petri dishes and melted agar medium maintained in the liquid state at a temperature of 45-50°C (agar solidifies below 42°C) added respectively in each Petri dishes. The bacterial suspension and the melted medium are mixed thoroughly. All Petri dishes then allowed to solidify and incubating in a BOD incubator.

• Lecture 19: Spread Plate Method 

  • This method is similar to the pour plate method (Fig. is given below). At first, the mixed culture of microorganisms is diluted by serial dilution method in a series of tubes containing sterilized saline water or buffer solution.

• Lecture 20: Streak Plate Method

  • This method is used most commonly to isolate pure cultures of bacteria. A small amount of mixed culture is placed on the tip of an inoculation loop/needle and is streaked across the surface of the agar medium. The successive streaks should be appropriate and separated from each other and not be overlapped on an agar medium surface.

• Lecture 21: Single Cell Culture Methods 

  • An individual cell of the required microorganism is picked out by this method from the mixed culture and is transferred in sterilized in a fresh medium to grow the pure culture. An equipment micromanipulator is used to pick on the cell or spore of a microorganism.

• Lecture 22: Enrichment Culture Method 

  • Select desired organisms through manipulation of medium and incubation conditions. It can prove the presence of an organism in a habitat.

• Lecture 23: Role of Soil Microflora Decomposition 

  • Zymogenous: opportunists; eat “easy” food; reproduce rapidly (r-strategists). Autochthonous: eat very resistant organic compounds; slowly reproducing (K-strategists)

• Lecture 24: Role of Soil Microflora in Biological Cycles

  • Biological cycle: Cyclical path elements, flow-through living (biotic) and non-living (abiotic) components in the environment, energy modified in different stages of the cycle, biomass produce, synthesis and breakdown of organic compounds, fixation, transformation, mineralization, etc. takes place.

• Lecture 25: Role of Soil Microflora in Mineralization 

  • Mineralization is complete biodegradation which involves the complete degradation of a compound to its mineral components, i.e., carbon dioxide and water. Mineralization is the opposite of immobilization

• Lecture 26: Nitrogen Fixation

  • Nitrogen is essential for the growth of all organisms. It is essentially inert due to the triple bond (N3), in order to use nitrogen for growth it must be "fixed".

• Lecture 27: Roles of Microbes in Organic Farming

  • Microbes provide nitrogen required for the plants through biological nitrogen fixation. Phospobacteria provides phosphorus required for plant growth by converting unavailable phosphorus to available form. Phosphorus uptake enhanced using Mycorrhiza fungi. Microbes provide plant growth-promoting substances. Microbes play an important role in controlling diseases of plants as Bio protectors.

• Lecture 28: Mycorrhizae

  • The symbiotic relationship between plants (roots) & soil fungi, Plant provides the fungus with energy (C), Fungus enhances soil resource uptake. This relationship observed with more than 80% of angiosperm plant spp. and fungi, all gymnosperms, sometimes an obligate relationship

• Lecture 29: Biological Control

  • An organism suppression growth of another organism like pathogen or pests, it is used in integrated pest control that does not depend on host resistance, sterilization of the target pathogen, or modification of pest behavior.

• Lecture 30: Bioremediation Agents

  • Soil bacteria break down toxic materials. They clean Environment Sometimes called as “superbugs” that involved in the quality improvement of the environment

• Lecture 31: Conclusive Lecture 

  • Microbes are not always pests and destructive to crops or animals but many microbes are beneficial. Microbes include fungi, bacteria and viruses are a very important role in nature. Soil microbes are essential for decomposing organic matter and recycling old plant material. In this way, they always improve the fertility of the soil. Some soil bacteria and fungi form relationships with plant roots that provide important nutrients like nitrogen or phosphorus. Fungi can colonize the upper parts of plants and provide many benefits, including drought tolerance, heat tolerance, resistance to insects, and resistance to plant diseases.

Know About Expert

Dr. Rajendra Prasad is working as Associate Professor of Agricultural Microbiology and Head of the Department, Uttaranchal College of Agricultural Sciences (UCAS) at Uttaranchal University, Dehradun. He had completed his M.Sc. Microbiology from H.N.B. Garhwal University, Uttarakhand in 2005 and awarded Ph.D. in Forestry (Forest Pathology) from FRI Deemed to be University, Dehradun, Uttarakhand in 2014. He has more than fifteen years of Teaching and Research experience in the field of Agricultural Microbiology and related subject areas. He had published 30 research articles in UGC listed, Scopus indexed and other reputed peer-reviewed national and international journals, authored 3 book chapters in renowned books, presented more than a dozen research papers in different conferences, seminars, workshops, etc. His major fields of research are Agriculture Microbiology, Mycology, Agricultural Biotechnology, and Forest Pathology. He had submitted technical reports of two research projects funded by Uttaranchal University and one consultancy project funded by an external client. Presently he is engaged in two ongoing consultancy Projects and doing research on biological control of some crop diseases along with routine teaching work at SOA, Uttaranchal University, Dehradun. He had also guided many students’ M.Sc. Thesis/ Dissertation Work.