2. Concept of
Microbial Ecology
Fundamentals of Microbial Ecology
Development of
Microbial Communities
Succession &
Colonisation
Microbial
Ecology
Relationship between
microorganisms & their
environments
Biotic Abiotic
3. Organisms occupying place – Sediment,
humus rich soil, nasal cavity, Intestinal
tract
Common
Terms in
Microbial
Ecology
Ecosystem Basic Unit of Ecology comprising of biotic
& abiotic components
Biotic element
Community of living organisms dealing
with populations of MO’s
Population Consisting of clones of one or several
species
Abiotic
Chemical & physical conditions for
microbial life
Habitat
5. Common
Terms in
Microbial
Ecology
Niche
생태적 지위
In general terms - organism lives
Functional role Survival Reproduction
No two population can occupy the
same niche at the same time
Cellulose- 셀룰로오스
Eg. Cellulolytic
bacteria
degrade cellulose
anaerobically
Gain energy by
fermentation 발효
Maintain themselves &
flourish in the rumen
6. Classification of microorganisms in ecosystem
Numbers
constant in
ecosystem
Autochthonous
Indigenous
토착
Present in given
ecosystem
Soil Intestine
Presence more or
less number based
on nutrient supply
Zymogenous Allochthonous
7. Found in
ecosystem at
very low number
Occasional
increase
Increase based
on specific
nutrient supply
Eg. Cellulolytic
microbes
High number
when soil
cellulose is high
Classification of microorganisms in ecosystem
Autochthonous Zymogenous Allochthonous
Cellulose- 셀룰로오스
8. Strangers in ecosystem /
not permanent
residents
Eg. Soil spores
of soil dwellers
Present in air for
short time period
for dispersal
Classification of microorganisms in ecosystem
Autochthonous Zymogenous Allochthonous
9. Concept of Microbial Ecology: Energy Flow
Use chemicals instead of
light
Ecosystems are in a
dynamic steady
state 역학 확고한
Controlling the
activity of individual
Maintaining
equilibrium 평형
Energy
Chemosynthetic
bacteria
Primary producer (use
light in photosynthesis to
reduce CO2)
10. Radiant Energy Chemical Energy
Sun Producers Consumers Decomposers
(Metabolism) (Metabolism) (Metabolism)
Heat Energy Heat Energy Heat Energy
“Primary
Productivity”
(Kcal/m2/day)
Stored energy in
primary producers
In the form of C
or OM
11. Mechanical Energy - two forms
Kinetic or free energy Potential energy
Moving Energy
Measured by the amount of
work done in bringing the
body to rest
Stored Energy
Useful after conversion into
kinetic energy
Organisms potential energy is
chemical energy of food
12. Grazing Food web
Herbivores
Carnivores
Omnivores
Detrivores
Detritus Food Web
Eat dead bodies or decaying
materials
Food oxidation Release energy Used to do work
Chemical Energy Mechanical Energy
Food Chain
Transfer of energy stored in organic
compounds from one organism to other
Energy transfer in
different steps
Trophic level
Food web
Interrelationship of
food chain
13. Bio-geochemical
Cycle (BGC)
Movement of material by
biochemical activities
Atmosphere
(air)
Hydrosphere
(water)
Lithosphere
(soil)
BGC cycle Physical (Precipitation, Fixation) &
Chemical transformation
(Biosynthesis, biodegradation) &
Combination of both
Microbes vital
role
Energy absorbed,
converted, temporarily
stored & Flow
C, H, O, N, P & S
15. Longer in natural environment if they are
absorbed than when they are free.
Extracellular polymeric substance
Consequence 결과적 of phenomenon 현상 of adhesion 부착
Organic & inorganic nutrients
Adsorbed surface of object
Extracellular enzymes
Absorbed microbial surface
Microbes
attachment
Prevent form predators
or from desiccation
Survival of viruses
& bacteriophages
16. Two stage process of attachment
Physical or chemical adsorption
Not controlled by the organism
Organisms secrete Protein or
Glycoprotein 당 단백질glue 아교
Adsorption 흡착 Adhesion 부착
To attracts similar species to
forming a colony
18. Negatively charged surfaces
at neutral pH owing anionic
groups (COO-) within their
wall polymers
Also negative charge due to
isomorphic (iso-equal, morphe-
shape) replacement.
Bacteria & fungi Soil Clay
These negative charged surfaces attract ions of
opposite charge in two layers
1) First layer is firmly
(Tightly 단단히) attached
2) Second layer is diffuse layer
attachment (100 nm distance
from surface)
Distance reduced to 0.5 nm in
concentrated solutions of polyvalent ions
(Na+ is univalent and Ca2+, Al3+ is
polyvalent)
19.
20. Attachment – either
“adsorbed” or “produced
by microbes”
The attachment charge is “directly
proportional to distance between them”
Effect surface
chemistry
Surface coating
of material
Surface Chemistry study of substances surfaces - adsorption,
the formation of colloids 콜로이드, heterogeneous catalysis,
corrosion 부식, dissolution, crystallization, etc.
At a given
ionic strength
Repulsion between
bacterium & surface
21.
22. The balance between the van der Waal’s forces
of attraction and the electro static repulsion
determines 결정 whether the bacterium is
attracted to the surface or repelled from it.
24. What is Community?
Highest biological Unit
Made up of Individuals &
Populations
What is Microbial
Community?
Assemblage of microbial
populations
Interacting between
them at given location
Habitat
Study of community -
Synecology
Study of individual &
population - Autecology
25. Heterogenicity of ecosystem is diversity
Various organisms occurring together
Important role in food web
Food energy move by multitude pathway if community is diverse
Loss of one species cause changes or collapse community
Increase of one species – rise of predator population
What is Diversity 종 다양성?
26. Dominant species determine the less & abundant species
1 or more population attain high number - Diversity decrease
What is Diversity 종 다양성?
Biological
communities
Few species with
many individuals
Many species with
few individual
Dominant species take most of energy
27. What Determines Diversity 종 다양성?
- Community has complex structure
More number of
species
Require low energy
Maintain ecosystem structure
Stable diversity
Dominant by
single species
Require more energy
To maintain stable condition
28. Diversity related to abundance of ecological niches.
Complex community offers a variety of ecological niches
than simple community.
Diversity inversely related to isolation.
Example: Islands 섬 less diverse than ecologically similar
continents 대륙 because difficult many species reaching
islands.
Diversity inversely 반대로 related to stress & extreme
environments
29. ‘Edge effect’ – Where two ecosystems overlap, the overlapping area
supports species from both, plus another species that is only found in
the overlapping area.
Diversity reduced when anyone species becomes dominant within a
community
So it is able to remove a disproportionate share of available resources
Thus preventing the growth of many other species.
30. Species Diversity Indices (SDI)
Several mathematical methods describe the species richness are
called Species Diversity Indices (SDI) which are used to describe
the assemblage of species diversity within a community.
But SDI cannot be applied to the microbial community due to
technical difficulties (quantitatively the data is insufficient).
32. Colonisation
First colonisers of a virgin
environment
Microbial growth & reproduction
on a material, animal or person
without damage
Primary succession
(first appearance of
MO’s)
Habitat not previously colonised
(eg. Gastro-intestinal tract of new
born)
Secondary succession
Succession occurs in a habitat with
a previous colonisation (volcanic
eruption, barren land 황무지, etc.)
Pioneer organisms
33. Pre-emptive Colonisation
Pioneer 개척자 organisms
alter the condition in the
habitat
New
Organisms
Populations better
adapted to the newly
colonised habitat
Replace the pioneers
Gradually secondary
invaders are also
replaced.
Succession ends when a relatively stable
community called a climax community is
achieved.
34. New Environment
Alter the condition
Pioneer organisms
Develop the
Environment
Not allowed further succession
Pre-emptive
colonisation
Altered habitat
Gradually secondary invaders
Succession ends
Stable community
Climax community
35. Climax community
No further changes
Difficult to apply the concept of
climax community to microbial
community
Because disturbance affect
successional processes
So not reaching full equilibrium
36. Succession
Later, some populations are replaced by other
populations that are better adapted to fill the
ecological niches.
Ecological niche
Community
Individual populations
Ecological niche Ecological niche
Then Later
Ecological niche
replaced by other populations
Communities of organisms not exist
suddenly but develop gradually by series
of stages until they reach maturity state.
Individual populations of a
community occupy the niches in
the ecosystem.
37. Succession is replacement of one
community by another as the condition
within the habitat changes
How its replaced?
Changes by the organism (by reduction
in nutrient & oxygen level or changes in
the pH) or changes from outside
New Environment
Pioneer organisms
Develop the
Environment
38. Some interrelationships loose associations where one microbial population
can replace the other (rhizosphere)
Some interrelationships tight associations where one microbial population
cannot replace another (symbiotic association of Rhizobium).
When it reach the Ecological stability
of the community?
Interrelationship among populations in a
community & adaptations within a
population contribute to the ecological
stability of the community.
New Environment
Pioneer organisms
Develop the
Environment
If microbes not have stability
Community continues..
39. Outcome of Succession
Each stage in a succession is
called sere Seral take long-term
New Environment
Pioneer organisms
Develop the
Environment
sere
sere sere
40. Eg. Bare rocks
Starting with
algae or lichens
Converted to
stable soils
At the start of the
sere
There is stress in the
environment (very low nutrient)
and the species diversity is low.
Bare rocks
41. Habitat is colonised
Number of species grow
increases
Reach climax (final
stage)
Dynamic equilibrium
between organism and
environment
Stable
42.
43. Stable communities
Example, communities in hot
thermal springs have a low species
diversity but are very stable
because of the environment.
Individuals species
come & go
Finally the balance
between the species vary
slight
The overall list of
organisms remain
stable.
Thus stability is not related to diversity
but it is imposed from outside
44. Hot summer
Favourable climate
No organisms disappear
Low species diversity, but stable
Succession occurs due to influence of physical & chemical changes
from outside the community.
Community succession begins with colonisation or invasion침입
of a habitat by microbial population.
45. Types of Succession
Autogenic succession
Example: Creation of anaerobic
conditions by facultative anaerobes
allows the growth of obligate anaerobes.
Microorganisms modify the
habitat
Permits a new population to
develop
Facultative anaerobes: grow with or
without oxygen because they metabolise
energy aerobically or anaerobically.
Obligate anaerobes: poisoned by oxygen, so
they grow low Oxygen
Allogenic succession Allogenic succession
46. Habitat is altered by environmental factors
Eg. salt marsh 바닷물이 드나 드는 늪 (zone between land & open salt water)
Then coastal marshes
converted completely into
terrestrial communities
Pioneer organisms
dominated by salt-loving
organisms (eg. Algae)
Grow & add organic
nutrients to the marsh
Followed by
nitrogen fixing algae
Types of Succession
Autogenic succession Allogenic succession Substrate succession
47. (eg. Porphyrosiphon notarisu, Gloeocapsa
spp., Gloecocystis spp., Nostoc muscorum)
Microbes involved in the development of
structured soils (eg. bare rock surfaces)
Low soluble minerals, no organic
matter & so high temperature &
moisture on the rocks
Uninhabited or
virgin environment
Pioneer organisms
Only tolerant algae & cyanobacteria
with mucilaginous walls (갑옷) or
slime capsule grow
Fix nitrogen
Types of Succession
Autogenic succession Substracte succession
Allogenic succession
48. Organic matter accumulates from
wind-blown dust & oxygen
Nutrients set back to zero (or) diversity
of microbes & nutrients support
growth of higher plants
Algae & lichens then fungi
& bacteria & then protozoa
These processes build up of primitive
thin soil which has more nutrients
(organic).
49. Which reflect the
colonisation of newly arrived
species of organic matter
Sere shortened if organic matter is added from outside
Long-term sere
(from primitive to
mature soil)
Many short-term changes
in the microbial
populations
Types of Succession
Autogenic succession Substracte succession
Allogenic succession
50.
51. High organic matter (OM)
in soil (plant litter &
animal bodies)
Mucor
Increase zymogenous population (Mucor, Rhizopus)
Among bacteria (Bacillus &
Pseudomonas)
Population slowly
changes to
ascomycetes,
actinomycetes &
protozoans.
Organisms degrade fungal hyphae. Fungus is part of
initial invasion (attack) of substrate
OM stimulate 자극하다
microbial spores [break the
dormancy (sleeping or quiescent)
of spores]
High competitive saprophytic
ability (live on dead or
decomposing matter)
Consumed easily
utilizable
substrates
pH drops due to
immobilisation of
cations
52. Species
diversity
decreased
Succession of
Final stage
Invasion (attack) by autochthonous organisms
especially those degrading lignin (supporting material
for algae tissues or plants)
During a substrate
succession
Activity of
microorganisms
increases
High environmental
diversity
Utilisable nutrients
used up & reduced
