Microbial interactions can be positive or negative. Positive interactions include mutualism, where both organisms benefit, and commensalism, where one benefits and the other is not affected. Negative interactions include competition, where resources are limited and both are harmed; amensalism where one is harmed; and parasitism where one benefits and the other is harmed. Examples of microbial interactions discussed include lichens as mutualism, gut bacteria as commensalism, and viruses as parasites. Microorganisms interact in complex ways that allow colonization of diverse environments.

1. SEMINAR TOPIC : MICROORGANISMS AND
MICROBIAL INTERACRION
Guide :
Dr.Pallavi M
Lecturer
Department of
Biotechnology
Sahyadri Science College
Shivamogga
Submitted By:
Yogesh H K
I MSc I Semester
Sahyadri Science College
Shivamogga

2. Dear Mother Earth How did you Born ?
How old are you?
Huh…
Its really herculean task to say about how I
come into existence and you don't know not an
ounce about astrophysics so let’s not get to the
topic….ask me something else but do
remember that I’m Slightly more than 4.8
Billion years old.
?

3. Ohk…Go on…
Yeah…You are right , Me being Biotechnology Student
won’t understand your birth mystery . Shall I ask one
more question?
When & How did life began on you ?
What was the first life on earth ?
Could you Answer my question?
Oooh… “ORIGIN OF LIFE ON EARTH” story is really
fascinating one. I will explain you in a simple way listen
carefully

4. The organic compounds i.e Carbon monooxide,Ammonia methane,
Amino Acids, CO2 etc were created spontaneously from inorganic
molecules in reductive oxygen less atmosphere from the action of sunlight
and lightening. The compounds were then dissolved in the primitive
ocean, concentrated, and underwent polymerization until they formed
“Coacervate” droplets. The droplets grew by fusion with other droplets,
were split into two daughter droplets and developed the ability to catalyze
their own replication through natural selection, which eventually led to
the emergence of life.
Life began with single-cell “Archaea and Bacteria” Since then, life has
evolved into a wide variety of forms. The whole process is called as “
Prebiotic Earth Theory” proposed by “A I Oparin and Haldane”.
Ohk…that’s damn interesting. Can you
show me that “Coacervate Droplet” and
scientists photo ?

5. A I Oparin and Haldane
Coacervate Droplets

6. Yes. Without Bacteria and Archaea its highly impossible to
imagine current world. Their presence on earth (archaea and
bacteria) changed Earth dramatically. They helped establish a
stable atmosphere and produced oxygen in such quantities that
eventually life forms could evolve that needed oxygen. The
new atmospheric conditions calmed the weather so that the
extremes were less severe. Life had created the conditions for
new life to be formed. This process is one of the great wonders
of nature.
So… What you are saying is “our real
ancestors are Bacteria and Archaea”

7. Hmm… I heard the terms “ Microorganisms and fungi
virus, algae , protozoa. What are these ?
Microorganisms means organisms which can not be
seen through naked eye but can be seen through only
microscope. And they are classified into 6 Types
1)Archaea
2)Bacteria
3)Algae
4)Fungi
5)Protozoa
6)Viruses

8. Hey Hai
Why didn’t you come to college? You know
what…. Pallavi mam finished off Important
chapter” Microorganisms and Microbial
Interaction”.
Ohh….no…I was sick so I couldn’t come to college.
Can you teach me about Microbial Interaction?
Ohk …will teach you now everything what I have
Iearnt but you don’t interupt me ….ohk ?

9. MICROBIAL INTERACTION

10. Microbial Interactions means Microorganisms interact with each other
and can be physically associated with other organisms in a variety of
ways. One organism can be located on the surface of another organism
as an ectobiont or located within another organism as endobiont.
There are two types of Microbial Interactions
1) Positive Interaction : Mutualism, Commensalism, Proto- cooporation
2) Negative Interction : Ammensalism, Parasitism, Predation,
Compitation

12. Type of interaction Effect of interaction
Population ‘A’ Population ‘B’
Commensalism 0 +
Mutualism + +
Competition + -
Amensalism 0/+ -
Parasitism + -
predation + -
0 = No effect
+ = Benefited
- = Adversely affected

13. Mutualism
• It is defined as the relationship in which each organism in interaction gets
benefits from association.
• It is an obligatory relationship in which mutualist and host are
metabolically dependent on each other.
• Mutualistic relationship is very specific where one member of association
cannot be replaced by another species.
• Mutualism requires close physical contact between interacting organisms.
Relationship of mutualism allows organisms to exist in habitat that could
not occupied by either species alone.
• Mutualistic relationship between organisms allows them to act as a single
organism

14. 01) Lichens: Lichens are excellent example of mutualism.
They are the association of specific fungi and certain genus of algae.
In lichen, fungal partner is called mycobiont and algal partner is called
Phycobiont is member of cycanobacteria ad green algae (Trabauxua).
Because phycobionts are photoautotrophs, the fungus gets its organic
carbon directly from algalpartner, in turn fungi protects the phycobiont
from extreme conditions and also provide water and minerals to algae.
Lichen grows very slowly but are able to colonies habitat that do not
permit the growth of other organisms. Most lichens are resistant to high
temperature and drying.
02) Protozoan-termite: Protozoan-termite relationship is the classical
example of mutualism in which flagellated protozoan lives in the gut of
termites. These flagellated protozoan feeds on diet of carbohydrates
acquired as cellulose or lignin by their host termites, metabolize into
acetic acid which is utilized by termites.
Examples

15. Lichens Microscopic View Protozoa and Termite

16. Commensalism
It is a relationship in which one organism (commensal) in the association
is benefited while other organism (host) of the association is neither
benefited nor harmed. It is a unidirectional association and if the
commensal is separated from the host, it can survive.
Non-pathogenic coli in intestinal tract of human:
E. coli is facultative anaerobes that uses oxygen and lower the O2
concentration in gut which creates suitable environment for obligate
anaerobes such as Bacteroides. E. coli is a host which remains
unaffected by Bacteroides.
Examples
Flavobacterium (host) and
Legionellapneumophila (commensal):
Flavobacterium excrete cystine which is
used by Legionella pneumophila and
survive in aquatic habitat.

17. Amensalism (Antagonism)
When one microbial population produces substances that is inhibitory to
other microbial population then this inter population relationship is known
as Ammensalism or Antagonism. It is a negative relationship. The first
population which produces inhibitory substances are unaffected or may
gain a competition and survive in the habitat while other population get
inhibited this chemical inhibition is known as antibiosis.
Examples
i. Lactic acid produced by lactic acid bacteria in vaginal tract:
Lactic acid produced by many normal floras in vaginal tract is inhibitory to
many pathogenic organisms such as Candida albicans.
ii. Skin normal flora: Fatty acid such as Lauric acid, sphingosine, and
dihydrosphingosine produced by skin flora inhibits many pathogenic
bacteria in skin.
iii. Thiobacillus thiooxidant: Thiobacillusthioxidant produces sulfuric
acid by oxidation of sulfur which is responsible to lowering of pH in the
culture media which inhibits the growth of most other bacteria.

18. Competition
The competition represents a negative relationship between two microbial
populations in which both the population are adversely affected with
respect to their survival and growth. Competition occurs when both
population’s uses same resources such as same space or same nutrition,
so, the microbial population achieve lower maximum density or growth
rate. Microbial population competes for any growth limiting resources
such as carbon source, nitrogen source, phosphorus, vitamins, growth
factors etc. Competition inhibits both populations from occupying exactly
same ecological niche because one will win the competition and the other
one is eliminated
Example
Competition between Paramecium cadatum and Paramecium
aurelia
Both species of Paramecium feeds on same bacteria population when
these protozoa are placed together.
P. aurelia grow at better rate than P. caudatum due to competition.

19. Parasitism:
It is a relationship in which one population (parasite) get benefited and
derive its nutrition from other population (host) in the association which is
harmed. The host-parasite relationship is characterized by a relatively a
long period of contact which may be physical or metabolic. Some parasite
lives outside host cell, known as ectoparasite while other parasite lives
inside host cell Known as endoparasite.
Example
i. Viruses:
Viruses are obligate intracellular parasite that exhibit great host
specificity. There are viruses that are parasite to bacteria (bacteriophage),
fungi, algae, protozoa etc.
ii. Bdellovibrio:
Bdellavibrio is ectoparasite to many gram negative bacteria. The parasite
Bdellovibrio penetrates the outer membrane of its host and enters
periplasmic space but not inside host cytoplasm.

20. iii. Mycoparasitism (Fungus-fungus interaction) :
Mycoparasitism, where one fungus attacks and invades another,
significantly contributes to suppression of pathogen population in nature,
and is applied in the biological control of plant diseases. ... review the role
of secondary metabolites in beneficial fungus-fungus interactions.
Mycoparasitisation of Rhizoctonia solani by
Trichoderma virens

21. Predation:
It is a wide spread phenomenon when one organism (predator) engulf or
attack other organism (prey).The prey can be larger or smaller than
predator and this normally results in death of prey. Normally predator-prey
interaction is of short duration.
Examples
i. Protozoan-bacteria in soil:
Many protozoans can feed on various bacterial population which helps to
maintain count of soil bacteria at optimum level.
ii. Bdellovibrio, Vamparococcus, Daptobacteretc are examples of predator
bacteria that can feed on wide range of bacterial population.

22. Conclusion
The microorganism–microorganism or microorganism–host interactions
are the key strategy to colonize and establish in a variety of different
environments. These interactions involve all ecological aspects, including
physiochemical changes, metabolite exchange, metabolite conversion,
signaling, chemotaxis and genetic exchange resulting in genotype
selection. In addition, the establishment in the environment depends on
the species diversity, since high functional redundancy in the microbial
community increases the competitive ability of the community,
decreasing the possibility of an invader to establish in this environment.
Therefore, these associations are the result of a co-evolution process that
leads to the adaptation and specialization, allowing the occupation of
different niches, by reducing biotic and abiotic stress or exchanging
growth factors and signaling.

23. Reference
01.Life Science Fundamentals and practicals II ( Seventh Edition) – Pranav
Kumar, Usha Mina Pathfinder Publication
02.https://www.dacollege.org/smat/micro-Microbial-Interactionn.pdf
03.https://www.infoplease.com/math-science/biology/genetics-evolution/origin-of-
prokaryotes-and-eukaryotes-origin-of-prokaryotes