1) The document discusses various types of biological interactions that can occur between microbial populations, including mutualism, commensalism, competition, and parasitism. 2) Mutualism provides benefits to both participating organisms and includes examples like rhizobium-legume symbiosis and mycorrhizal associations. 3) Commensalism benefits one organism without affecting the other, while competition negatively impacts both interacting populations by limiting shared resources. 4) Parasitism benefits one organism (the parasite) at the expense of the other (the host).

1. PRESENTING BY :
Y.SANTHOSHI LAVANYA
2020611005
AGRICULTURAL MICROBIOLOGY

2. Many microbial populations interact and establish associations with each other
and with higher organisms.
These interactions are inter and intra relationships between various
microorganisms. This can include both positive and negative interactions.
They are ubiquitous, diverse and critical important in the function of any
biological community.
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3. SYMBIOSIS : living together
It is close and long term or short term biological interaction between two
different species.
The term symbiosis is coined by Anton de Bary.
It can be obligatory, which means that one or both of the symbionts entirely
depend on each other for survival, or facultative when they can generally live
independently.
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4. DIFFERENCE BETWEEN SYMBIOSIS AND MUTUALISM
Symbiosis is an ecological interaction
between at least two species where there
is persistant contact between the
partners
Mutualism is an ecological interaction
between at least two species where
both partners benefit from the
relationship
All mutual relationships are symbiotic relationships, but not all symbiotic relationships
are mutual relationships
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6. BIOLOGICAL INTERACTIONS
NEUTRAL
INTERACTIONS
POSITIVE INTERACTIONS
 MUTUALISM
 COMMENSALISM
 PROTO CO-OPERATION
NEGATIVE INTERACTIONS
 ANTAGONISM
 COMPETITION
 PREDATION
 PARASITISIM
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7. Neutralism describes the relationship between two species that interact but
do not affect each other
Neither of the population is affected by interaction with each other
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9.  It is a type of symbiotic interaction in which each organism benefits from the
association.
 It is an obligatory relationship.
 Highly specific.
 They operate as a single organism
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10. 1) Rhizobium-legume association
2) Mycorrhizae
3) Herbivore microbial association
4) Lichens
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11.  Mutualistic interaction can be seen in the
symbiotic nitrogen fixation of rhizobium
associated with root nodules of leguminous
plants is the best example.
 Bacteria supply nitrogen to plant.
 Plant supply carbon to bacteria
Rhizobium-Legume association
Selim et al., 2003
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12. Singh et al., 2019
Rhizobium-Legume Symbiosis
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13.  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.
 Because phycobionts are photoautotrophs, the fungus
get its organic carbon directly from algal partner, in turn
fungi protects the phycobiont from extreme conditions
and also provide water and minerals to algae.
Lutzoni et al., 2001
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14.  It represents a mutualistic symbiosis between the
root system of higher plants and fungal hyphae.
 It is of two types
1. Ectomycorrhizae : the fungal hyphae form a
sheath over the outside of the roots.
2. Endomycorrhizae : the fungal hyphae invade the
root cells without forming any external sheath
Zayed et al., 2013
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16. Role of Rhizobium, a plant growth promoting bacterium, in enhancing algal biomass through
mutualistic interaction
Dominant bacterial OTUs detected in the phycosphere 16S
rRNA gene clone libraries.
1: Chlamydomonas reinhardtii AG 20446; 2: C. vulgaris AG
10032; 3: Scenedesmus sp. AG 20831; 4: B. braunii UTEX
572.
Promotion of green algal growth by Rhizobium sp.
Square: C. reinhardtii; diamond: C. vulgaris;
triangle: Scenedesmus sp.; circle: B. braunii.
Closed: Rhizobium co-cultivation, Open: Control cultures.
Kim et al., 2014
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17.  It refers to a relationship between organisms in which one species of a
pair benefits , the other is not affected.
 Unidirectional association.
 If the commensal is separated from the host , it can survive.
 It is not an obligatory
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18.  Population of Mycobacterium vaccae , while
growing on propane , cometabolizes cyclohexane
which is then used by other bacterial populations
, Pseudomonas
 The latter population is thus benefited since it is
unable to oxidise cyclohexane to cyclohexanone
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19. Metabolic Commensalism and Competition in a Two-Species Microbial Consortium
Time course analysis of biofilm thickness when P. putida
R1 and Acinetobacter strain C6 (F) were grown as
monoculture biofilms or when the two strains were grown
as mixed biofilms (Œ).
Time course analysis of the numbers of P. putida R1 and
Acinetobacter strain C6 (F) cells collected from chemostats
where the strains were established either as monospecies
cultures (A) or as mixed cultures (B)
Christensen et al., 2002
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20.  It is a relationship in which organism in association is mutually benefited with each other.
 This interaction is similar to mutualism but the relationships between the organisms in
protocooperation is not obligatory as in mutualism.
 It is also called as Synergism.
 In this relationship microbial populations perform a function which may not be performed
individually or produce a new product that neither each population can produce alone.
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21. Association of Desulfovibrio and Chromatium: it is a
protocooperation between carbon cycle and sulfur
cycle.
Interaction between N2-fixing bacteria and
cellulolytic bacteria such as Cellulomonas
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23.  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.
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24.  The production of antibiotics that can inhibit
or kill a susceptible microorganism .
 Penicillin, (Pencillium notatum) produces n
antibiotic compound inhibits the growth of
many species of bacteria (Ex: Staphylococcus
aureus) by interfering with the normal
normal formation of peptidoglycan in the
cell wall.
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25. Antagonistic Activities of Soil-Borne Bacillus spp. and Pseudomonas spp. against
Phytophthora infestans
(A) Pectobacterium carotovorum, (B) Phytophthora infestans, (C) Alternaria solani, (D) Fusarium solani,
and (E) Rhizoctonia solani.
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Caulier et al., 2018

26.  The competition represents a negative relationship between two microbial population in which both the
population are adversely affected with respect to their survival and growth.
 Competition occurs when both population 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 population from occupying exactly same ecological niche because one will win
the competition and the other one is eliminated.
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27.  Both species of Paramecium feeds on
same bacteria population when these
protozoa are placed together.
 P. aurelia grow at better rate than P.
Gause, 1934
Competition between Paramecium cadatum and Paramecium aurelia:
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28.  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.
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29.  The parasites which can live in hosts if it is available , but capable of living independently if
its host is not available.
 Ex: The fungus Ceratocystis ulmi , which causes Dutch elm disease , kills the tree and then
lives saprophytically on its dead remains
 The parasite which depend upon the specific host through out the life
 Ex : Downy mildews , Powdery mildews
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30. MYCOPARASITISM
 When one fungus parasite's other it is referred
as mycoparasitism.
 It is classified into two groups:
1. Necrotrophic: It makes contact with its host
,excretes toxic substance which kills host cells
and utilizes the nutrients that are released.
2. Biotroph: It is able to obtain nutrients from the
living host cells.
 Trichoderma is an important example
Druzhinina et al., 2011.
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31. Identification of signatory secondary metabolites during mycoparasitism of Rhizoctonia
solani by Stachybotrys elegans
Number of identified Rhizoctonia solani (R)-derived and
Stachybotrys elegans (S)-derived metabolites during their
mycoparasitic interaction 4 and 5 days following dual-
culturing.
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Chamoun et al., 2015

32.  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.
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33.  Bdellovibrio bacteriovorus is a
predatory bacterium, which
cell wall and multiplies between the
the plasma membrane, which causes
the prey and releases its progeny.
 It attacks and consumes different
strains, including Escherichia coli and
Aquaspirillum serpens, Salmonella
typhimurium, and Helicobacter
pylori.
(Dwidar et al., 2012)
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35. Soil harbors great diversity of microorganisms; this diversity is responsible for biological
equilibrium created by the associations and interactions of all individuals found in the
community.
Plants are the main responsible for most of these interactions due to their root exudates.
These interactions perform significant roles on plant growth and health and the ecological
fitness and resistance of plants to different biotic and abiotic stresses in soils.
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