Bacterial-Fungal interactions & their imapct on other organisms and environment.

2.  In many environments, bacteria &
fungi coexist and interact.
Furthermore these Bacterial-Fungal
Interactions(BFIs) often have
important branching for the biology
of the interacting partners.
 Simultaneous studies have revealed
that fungi & bacteria often form
physically and metabolically
interdependent association that
harbor properties distinct from those
of their single components.
 There are multiple practical
relevancis of BFI to an exceptionally
diverse variety of fields, including
agriculture, forestry, environmental
protection, food processing,
biotechnology, medicine, dentistry.
INTRODUCTION :

3.  Associations between fungi & bacteria exist in many different
perspectives.
 Such as, they interact by forming physical complexes between
them or by molecular communication.
Different modes of
bacterial-fungal
interactions :

4.  Complexes containing bacteria & fungi
are found in many distinct
environments,
 Such as the lungs of cystic fibrosis
patients, the human oral cavity, the
production of foods such as wine,
cheese, temph (deep frying fermented
soya beans) and agricultural & forest
environments.
 The physical associations between them
can range from seemingly disordered
polymicrobial communities to highly
specific symbiotic associations of
fungal hyphae & bacterial cells.
BFI BY FORMING
‘PHYSICAL
COMPLEXES’
BETWEEN
BACTERIA & FUNGI :

5.  Interactions via Antibiosis : Probably the best known bacterial-
fungal communication is antibiosis, a chemical mechanism that is
characterize by the diffusion of deleterious & often chemically complex
molecules from one partner to the other.
 The most famous of which is the beta-lactam antibiotic PENICILLIN,
which was developed based on the antibiosis of a Penicillium mold
contaminating Staphylococcus culture.
BFI by molecular interactions
& communication :

6.  Migration & physical contact are also
important processes in the establishment
of BFIs.
 Chemotaxis is a directed movement of
bacteria towards fungi. In the case of
chemotatctic response of the biocontrol
strain Pseudomonas fluorescens,
Fusarium oxysporum fusaric acid has
been identified as an important fungally
derived chemotactic signal.
 Cell-cell contact between fungi &
bacteria can result in important changes
to their physiology.
Interactions via
Chemotaxis &
cellular contacts :
Adhesive interactions mediated by
polysaccharide for the attachment by
Pseudomonas bacteria with antifungal
activity onto the hyphae of the button
mushroom Agaricus bisporus have been
reported.

7.  Effects on Fungal Development :
Extracellular bacteria can affect fungal
development and spore production, to the
benefit or the detriment of the fungus.
 The commercial production of mushrooms
occur via the initial colonization of
mushroom compost by the fungal mycelium
followed by casting with a layer of a
peat/limestone mix that stimulates fruiting
body initiation. The presence of bacteria,
notably Pseudomonas putida in this casing
layer is highly beneficial for the induction of
mushroom production by Agaricus bisporus.
CONSEQUENCES OF BFI
FOR PARTICIPATING
ORGANISMS :

8.  Interactions have different outcomes depending upon the
physiological or developmental stages in which the two partners
meet. A good example of this is seen in mushroom production by
Agaricus bisporus is partly depend on Pseudomonas putida in the
casing layer. However, pseudomonas also cause disease on
mushroom, resulting in symptoms such as brown blotch, ginger
blotch, and drippy gill.
COMPLEXITY IN LIFE
CYCLE :

9. IMPACT ON
OTHER
ORGANISMS
&
ENVIRONMEN
T

10.  Effects on Animals : BFIs in the digestive tracts of ruminant
mammals, where bacteria are play a major role because of their
metabolic diversity, while ruminal fungi, although less numerous,
are able to weaken & degrade the more recalcitrant plant tissues by
their secretion of different polysaccharide -hydrolyzing enzymes.
 A clear beneficial role for BFIs in host nutrition is found in the
mutualism between “fungus-gardening”(attine) ants & their fungal
associates.
INFLUENCE ON HOST
NUTRITION :
Fungus gardens may come under
attack from members of the
ascomycete genus Escovopsis.
The ants keep their gardens free
from microbial pathogns due to
the host benificial BFIs. Attine
ants support populations of
actinomycete bacteria
(Streptomyces), which produce
antibiotics that antagonize the
parasitic Escovopsis populations.

11.  Effects on Humans : Human gut microbial communities are
thought to play a major role in health & disease. The level of fungal
diversity in human gut is almost certainly lower than the level of
bacterial diversity. Fungi may play unique functional role in the gut
that are complementary to those ascribed to bacteria, such as nutrient
release & exchange. However, the extent to which the fungi &
bacteria interact in the human gut is largely undetermined.
INFLUENCE ON HOST
NUTRITION :
A culture independent rRNA
oligonucleotide fingerprinting
approach for the murine in
intestine suggested that an
abundant & diverse fungal
microbiota is likely to be
present.

12.  Fungi & bacteria play central roles in
terrestrial ecosystems, where they
participate in numerous biochemical
cycles.
 Wood decay by the white rot fungus
Heterobasidion annosum was shown to
inhibited or promoted by bacteria found
in association with it.
 Bacteria may also provide nutritional
benefits to wood degrading fungi
e.g. By N2 fixation in the surrounding
soil that the fungal hyphae can transport
to the site of wood degradation.
ROLES IN BIOCHEMICAL CYCLES
& THE ENVIRONMENT :
BFIs also contribute to cycling
on inorganic nutrients. In
nutrient-poor soil inorganic
minerals are derived from
weathering from rocks with the
help of mycorrhiza-associated
bacteria & mycorrhizal fungi.

13.  FERMENTATION & BREWING : Mixed
bacterial-fungal communities play a key role in
determining the taste, quality, & safety of a wide
range of foods. The complex interactions
between filamentous fungi, yeast, & bacteria
that lead to wine production.
 CHEESE RIPENING : Like wine production,
cheese manufacture involves complex microbial
ecosystems where BFIs play a central role & rich
mixed communities are often present. They
utilize lactate & thus deacidify the cheese
surface, enabling the establishment of less-acid-
tolerant bacterial communities, which play a
significant role in the equality & safety of the
final product. E.g. German “Limburger” cheese.
APPLICATIONS OF
BACTERIAL-FUNGAL
INTERACTIONS :

14.  The microbial degradation of Polycyclic Aromatic
Hydrocarbons (PAHs) has significant potential for use in
bioremediation.
 Moreover, they significantly reduced the mutagenicity of
contaminated soils with Benzo[a]pyrene or
Dibenz[a,h]anthracene.
 Bacterial-fungal co cultures have also been found to have an
enhanced ability to decolorize waste azo dyes that cause
environmental pollution, while a mixed bacterial-fungal
biofilm of Penicillium frequentans & Bacillus mycoides
demonstrated a greater ability to degrade polyethylene than
either partner alone.
 This results highlight the fact that bacteria & fungi can
cooperatively mineralize soil pollutants.
BIOREMEDIATION OF POLLUTANTS
:

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 2. Addis, E., G. H. Fleet, J. M. Cox, D. Kolak, and T. Leung. 2001.
The growth, properties and interactions of yeasts and bacteria
associated with the maturation of Camembert and blue-veined
cheeses. Int. J. Food Microbiol. 69:25–36.
 3. Adesina, M. F., R. Grosch, A. Lembke, T. D. Vatchev, and K.
Smalla. 2009. In vitro antagonists of Rhizoctonia solani tested on
lettuce: rhizosphere competence, biocontrol efficiency and rhizosphere
microbial community response. FEMS Microbiol. Ecol. 69:62–74.
 4. Aho, P. E., R. J. Seidler, H. J. Evans, and P. N. Raju. 1974.
Distribution, enumeration, and identification of nitrogen-fixing
bacteria associated with decay in living white fir trees. Physiopathology
64:1413–1420.
REFERENCES :