Soil Microbiology_MSP. related to microbes present in soil
- 2. SOIL MICROBIOLOGY • Soil microbiology is the study of organisms in soil, their functions, and how they affect soil properties. • Microorganisms in soil are important because they affect soil structure and fertility. • Soil microorganisms can be classified as bacteria, actinomycetes,fungi, algae and protozoa
- 3. SOIL SAMPLE UNDER MICROSCOPE
- 4. MICROBIAL DISTRIBUTION IN SOIL Earthworms 12% other macro fauna 5% Other micro flaura(eg:fung i and algae) 40% Bacteria and Actinomycete s 40% Mesofauna (invertebrates between 0.1mm and 2mm in size) 3%
- 5. 1.BACTERIA
- 6. • Bacteria and Archaea are the smallest organisms in soil apart from viruses. • Bacteria and Archaea are prokaryotic. All of the other microorganisms are eukaryotic. • Most soil bacteria live close to plant roots and are often referred to as rhizobacteria(lives on rhizosphere)
- 7. Biochemical processes of bacteria Nitrogen fixation(Nitrobacter sp.) Degradation (Sulphur degradation, hydrocarbon degradation etc) Used forremediation (Pseudomonas sp. etc)
- 8. RHIZOSPHERE • the zone of chemical, biological, and physical influence generated by root growth and activity • Exudates: carbohydrates and proteins secreted by roots. Attracts bacteria, fungi, nematodes, protozoa.
- 9. EXAMPLES: : Some genera like • Pseudomonas, • Arthrobacter, • Clostridium, • Achromobacter, • Sarcina, • Enterobacter etc.
- 10. PICS:
- 11. 2.ACTINOMYCETES
- 12. • Actinomycetes are a fungi-like bacteria forming long filaments that stretch through the soil. • Actinomycetes live predominantly aerobically and are heterotrophs. • They have sometimes been classed as fungi because they both look similar, and decompose similar material as fungi.
- 13. • Antibacterial agents work against them but antifungal agents do not. • Make “earthy” smell by producing geosmin • Adaptable to drought • Can act in high pH • Break down “recalcitrant” compounds
- 14. • One of the most notable characteristics of the Actinomycetes is their ability to produce antibiotics ,like Streptomycin
- 15. EXAMPLES: • Nocardia asteroides • Dermatophilus congolensis • Streptomyces etc.
- 16. PICS:
- 17. 3.FUNGI
- 18. • Fungi are important in the soil as food sources for other larger organisms, pathogens, beneficial symbiotic relationships with plants or other organisms and soil health. • Most of the environmental factors that influence the growth and distribution of bacteria and Actinomycetes also influence fungi.
- 19. • The quality as well as quantity of organic matter in the soil has a direct correlation to the growth of fungi, because most fungi consume organic matter for nutrition. • Fungi thrive in acidic environments, while bacteria and Actinomycetes cannot survive in acid.
- 20. EXAMPLES: 1.Saprophytic fungi (decomposers) – Pleurotus ostreatus (oyster mushroom) – Lentinula edodes (shiitake) – Stropharia rugosoannulata (king Stropharia). 2. Mutualists Fungi – Zygomycota – Basidiomycota
- 22. PICS:
- 23. 4.ALGAE
- 24. • Filamentous, colonial, unicellular • Photosynthetic • Algae can be split up into three main groups: – Cyanophyceae – Chlorophyceae – Bacillariaceae • Blue-green algae(Cyanophyceae) are responsible for nitrogen fixation.
- 25. EXAMPLES: • Cyanophyta (Blue-green algae) • Chlorophyta (Grass-green algae) • Xanthophyta (Yellow-green algae) • Bacillariophyta (diatoms or golden- brown algae)
- 26. PICS:
- 27. 5.PROTOZOA
- 28. • Protozoa are eukaryotic organisms • The first microorganisms to reproduce sexually, a significant evolutionary step from duplication of spores, like those that many other soil microorganisms depend on.
- 29. • Protozoa can be split up into three categories –Flagellates –Amoebae –Ciliates.
- 30. EXAMPLES: • Flagellates –(e.g., Giardia lamblia) • Amoeboids –(e.g., Entamoeba histolytica) • Sporozoans –(e.g., Plasmodium knowlesi)
- 31. PICS:
- 32. IMPORTANCE OF SOIL MICROBES • Organic matter decomposition and soil aggregation; • Breakdown of toxic compounds • Inorganic transformations that make available nitrates, sulphates and phosphates as well as essential elements such as Fe and Mn;
- 33. • N fixation into forms usable by higher plants. • Mycorrhizae or root fungi form a dense network of thin filaments that reach far into the soil, acting as extensions of the plant roots they live on or in. • Pathogenic microbes are also there but beneficial is out numbered
- 34. DESTRUCTION OF SOIL MICROBES • Natural disturbances – Wind and water erosion – Flood – Fire – Seasonal changes • Disturbances due to land management – Chemical fertilizers and pesticides used for cultivation. – Vehicles used for cultivation
- 35. • Disturbances associated with dispersal of waste and industrial activities. – Sewage sludge and manure – Elevated levels of atmospheric carbon dioxide. – Plastic wastes
- 36. Soil microbes and plant growth • best medium forplantgrowth. • convert complex organic nutrients into simpler inorganic forms which are readily absorbed by the plant forgrowth. • produce variety of substances like IAA, gibberellins, antibiotics etc. which directly or indirectly promote the plantgrowth.
- 37. Biological nitrogen fixation microorganisms fix 60% nitrogen for requirement of plants Two groups of microorganisms are involved in the process of BNF Non-symbiotic (free living): aerobic heterotrophs ( Azotobacter, Pseudomonas, Achromobacter) aerobic autotrophs (Nostoc, Anabena, Calothrix, BGA) anaerobic heterotrophs (Clostridium, Kelbsiella. Desulfovibrio) o anaerobic Autotrophs (Chlorobium, Chromnatium, Rhodospirillum, Meihanobacterium etc)
- 38. Cont’d Symbiotic (Associative): Rhizobium, Bradyrhizobium in legumes (aerobic): Azospirillum (grasses), Actinomycetes
- 39. Figure 27.1 Mycorrhizae Fungi living in close association with plant roots Extend surface area of roots
- 40. Commercial use of mycorrhizae
- 41. Biogeochemical Cycles and microbes Biogeochemical cycles: Recycling (oxidation and reduction) of chemical elements carbon cycle (roleof microoganisms in this cycle) nitrogen cycle(role of microorganisms in this cycle) ammonification, nitrification, denitrification, and nitrogen fixation. sulfurcycle (roleof microorganisms in thiscycle)
- 42. Carbon cycle
- 44. Nitrogen cycle
- 46. N2 Nitrogen fixation Ammonia (NH3) Nitrate ion (NO3 -) Pseudomonas N2 2 Nitrite ion (NO -) Nitrobacter 3 Nitrate ion (NO - ) Ammonium ion (NH4 +) Nitrosomonas 2 Nitrite ion (NO - ) Aminoacids (–NH2) Microbial ammonification Ammonia(NH3) Microbial decomposition Proteinsand wasteproducts Aminoacids The Nitrogen Cycle
- 48. Nitrogen Fixation In root nodules Rhizobium Bradyrhizobium Frankia
- 49. The Formation of a Root Nodule
- 51. The Sulfur Cycle
- 53. Aminoacids Microbial decomposition Proteinsand waste products Microbial dissimilation Aminoacids (–SH) H2S H2S Thiobacillus SO4 2– (forenergy) SO4 2– Microbial & plantassimilation Aminoacids The Sulfur Cycle
- 54. Soil microorganisms as biocontrol agents Trichoderma sp. and Gleocladium sp. are used for biological control of seed and soil bornediseases Fungal genera Entomophthora, Beauveria, Metarrhizium and protozoa Maltesiagrandis Malameba locustiae etc are used in the management of insect pests. Bacteria like Bacillus thuringiensis, Pseudomonas are used in cotton against Angular leaf spot and boll worms.
- 55. The Degradation/Detoxification of Synthetic Chemicals Natural organic matter is easilydegraded by microbes Degradation/detoxification of the toxic chemicals or pesticides: Clostridium, bacterial Bacillus, genera like Pseudomonas, Thiobacillus, Achromobacter etc. and fungal genera like Trichoderma, Penicillium, Aspergillus, Rhizopus, and Fusarium Biodegradation of hydrocarbons: Natural hydrocarbons in soil like waxes, paraffin’s, oils etc are degraded by fungi, bacteria and actinomycetes. E.g. ethane (C2H6) a paraffin hydrocarbon is metabolized and degraded by Mycobacteria, Nocardia, Streptomyces, Pseudomonas, Flavobacterium and several fungi
- 57. Prospectives of Microbes in soil Bioremediation: Use of microbes to detoxify or degrade pollutants; enhanced by nitrogen and phosphorus fertilizer Bioaugmentation: Addition of specific microbes to facilitatedegradation of pollutant Biostimulation: Practice of addition of nitrogen and phosphorus to stimulate indigenous microorganisms in soil. Bioventing: Process/way of Biostimulation by which gases stimulants like oxygen and methane are added or forced into soil to stimulate microbial activity Composting:matter treated with aerobic thermophilic microorganisms todegrade contaminants