1.
Presentation of Environmental
Biology
Submitted to: Dr. Sagheer Ahmed
Submitted by: Amna Azam Javied
Roll no. : 857
Semester: 8th
Department: Zoology
Topic: Interaction between microorganisms

2.
The inter- and intra-relationships between various
microorganisms which can include both positive
(like SYMBIOSIS) and negative (like ANTIBIOSIS)
interactions.
Examples include virus - bacteria and bacteria -
bacteria.
The associations are very important biologically.

3.
These includes:
oNeutralism
oMutualism
oCommensalism
oParasitism
oCooperation
oPredation
oAmensalism
oCompetition
oSynergism

4.
Types of interactions
• Positive interaction: Mutualism, Syntrophism,
Proto-cooperation, Commensalism
• Negative interaction: Ammensalism
(antagonism), parasitism, predation,
competition

5.
PARTNERS INVOLVED:
MICROBE-MICROBE INTERACTION.
MICROBE-PLANT INTERACTION.
MICROBE-ANIMAL INTERACTION.
MICROBE-HUMAN INTERACTIONS.
MICROBE-ENVIRONMENT INTERACTIONS AND
DISEASES.

6.
NEUTRALISM
Microorganisms have no effect on each
other.
o Observed in natural communities if,
 Culture density is low.
 Nutrient level is high.
 Each culture has distinct
requirements.
 Example: Bread mold penicillium

7.
Mutualism
•An obligatory relationship.
•Highly specific.
•They operate as a single organism.
•Both organisms benefit.
•For Eeg.Diatom(Climacodium)
•and cyanobacteria(Epithemia turgida)
•Lichen-Fungi with Cyanobacteria.

8.
Cooperation
• Positive but not obligatery symbiosis.
• Can be separated from one another.
• For eg-Desulfovibrio & Chromatium,Cellulomonas &
Azotobactor.

9.
Commensalism
 One partner(commensal) benefits.
 while other(host) remains unaffected.
 – Common among organisms, not obligatory
 – Unidirectional
 – Usually, unaffected population modifies the
environment in a way that other population
benefits.
 For eg-during Nitrification ,oxidation of NH4+ ions
get convert into nitrate.
 Nitrosomonas convert NH4+ Ions to nitrite and
nitrobacter oxidise nitrite into nitrate.

10.
Parasitism
 One speices is dependent on a another for
nutrition and growth.
 In it, one organism is benefitted and other is
harmed.
 Closly related to predation.
 Coexistence between host and parasite.
 For eg-Viruses are the highly specialized
intracellular parasites,generally kill the host.

11.
Conti….
Cell.
 Myxococcus xanthus and E.coli.
 Microbial parasite may kill the host or can have stable
relationship without killing the host.(lysogeny provirus
is carried on host chromosome).
 Pathogenic parasite may attack and kill the plant or
animal host.
 Obligate parasite Treponema
pallidum(syphilis),Rickettsia(Rockey mountain fever)
can’t grow without an appropriate host.

12.
Predation
 It involves predator species which target other
microbe for material to survive.
 attacks and kills its prey.
 They can be obligate or facultative.
 Members of predatory bacteria are known as
‘Bdellovibrio and like organisms’(BALO).They can be
epibiotic,periplasmic,cytoplasmic.
 For eg-
 Bdellovibrio-E.coli interaction
(Vampirococcus,Daptobacter both attack
Chromatium.

13.
Amensalism
 Focuses on exclusion of an organism from growing
on a specific site to prevent the utilization of limiting
nutrients.
 Unidirectional process based on the release of a
specific compound by one organism that has
negative effect on another.
 Product of one impact another i.e one species
remains uneffected while other is harmed.
 For eg- microbial production of antibiotics that can
inhibits or kill another.penicillin by fungi inhibit a
type of cell wall found

14.
Conti….
only in bacteria.
 Bacteriocins-kill the strains of closely related
species by generating holes in plasma membrane.
 Metabolic end products.

15.
Competition
 It arises when different organisms within population
try to acquire same resources.
 Both the species are harmed.
 Competition within the species or among different
species can be attributed to availability of Nitrogen
source, carbon source, electron donors, electron
accepter, vitamins, light, water.
 Competition may result in exclusion of other species
or the establishment of a steady state where
multiple species coexist.

16.
Conti…
 Eg- In aquatic environment where extensive
phototrophic activity results in blooms of single
species of diatoms or cyanobacteria.
 Thermophilic springs chemolithotrophic
organisms are selected.
 Lactic acid fermentation of food.
 Large intestine of animals, a single species
doesn’t dominate but a mixed population coexist.

17.
Syntropism
 Two species are required for growth on a specific electron
donor that is not metabolized by either organism alone or one
of the organisms remove end products of metabolism from
other, which enables both the organisms to grow.
 Both the species are benefited.
 This relationship was discovered by Meyer Wolin and
colleagues, when fermentation of propionic acid occurred
when there was a coculture.
 Synophobacter produces H during fermentation and
accumulation of H makes the reaction thermodynamically
unstable.
 Pesence of methanogen, Methanospirillum makes the
oxidation favourable by consuming the H.’

18.
Microbe-Plant Interactions
 Different interactions between microorganisms and
plants have been identified and the most obvious
environment for such interactions is soil.
 Microbe-plant association can be mutulistic(a
highly specialized interaction where there is
considerable specificity found in mutulistic
activities)or it can be commensilistic(secretions
from plants benefit bacteria and fungi but no
apparent benefit to plant.

19.
Bacteria-Root nodule system
 Enzyme system for N2 fixation is present only in
prokaryotes and nodules are associated with roots of
Leguminous plants,bacteria(rhizobia) are specific for
a legume species.
 Assciation is beneficial for both,plant provide c and
energy source to bacteria and bacteria fix N2 and
provide amino acid to plant.
 Rhizobium leguminosarum sp.and pea, beans
tropical(root nodules).
 Azorhizobium caulinodan and Aquatic tropical
legume(stem nodule).

20.
Microbe-Animal Interaction
 Bacteria and fungi interact with humans and other animals and this
interaction can be symbiotic, commensalistic or parasitic.
 Symbiotic relationships are widespread and has evolved new
metabolic capabilities and cellular structures.(symbiogenesis).
 Evolutionary benefits in a symbiotic relationship are;-provision of
dietary needs that their hosts lack including essential amino acids,
cofactors, metabolic factors etc.
 N storage and recycling.
 Large alterations in genome of symbionts and adaptations by host
to favour the symbiosis occur during long association which can be
in form of genome size reduction or increase in AT content in
genome. since endosymbionts protect their hosts from pathogens,
this may have influenced the evolution of sociality in animals to
acquire the endosymbiont through horizontal and vertical
transmission.