Related to soil microbiology

1. SOIL
MICROBIOLOGY

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

21. 3.Pathogenic fungi
– Pythium,
–Rhizoctonia,
–Phytophthora
–Verticillium.

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

45. The 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

47. Nitrogen Fixation
In rhizosphere
Azotobacter
Beijerinckia
Clostridium
pasteurianum
Cyanobacteria:
heterocysts

48. Nitrogen Fixation
In root nodules Rhizobium
Bradyrhizobium Frankia

49. The Formation of a Root Nodule

50. Nitrogen Fixation
In lichens
Cyanobacteria

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

56. Microbial
Decomposition of
Herbicides

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