10 ekosistem mikroba 2015
TRANSCRIPT
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The role of microorganisms ?
producers consumers
decomposers
- the decomposition of pollutants and toxic wastes
- the efficient utilization of limited natural resources
- transformations of chemical substances that can
be used by other organisms
Help in
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• critically important to all form of life
closely linked with the flow of energy
• the ultimate source of all carbon is CO2
- raw material for photosynthesis
- major waste product of respiration andcombustion
Carbon Cycle
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Org. C.
CO
2
CH
4
CO
2
Anaerobic
Aerobic
CO
2
fixation
CO
2
fixation
Respiration
Anaerobic
respiration and
fermentation
Org.
C.
Methanogenic
procaryotes
Methane-oxidizing
procaryotes
(phototrophic
bacteria)
(anaerobic m.o.)
(cyanobacteria,
algae, plants, and
chemoautotrophic
procaryotes)
(animals, plants,
and m.o.)
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Nitrification
Organic nitrogen
NH
3
Anaerobic
Aerobic
Nitrogen fixation
Denitrification
NO
2
-
N
2
NO
3
-
NO
2
-
N
2
O
N
2
Nitrogen fixation
Assimilation
Ammonification
(Pseudomonas)
(Klebsiella)
(Nitrosococcus)
(Rhizobium)
(Nitrococcus)
Assimilation
Anammox
(
Brocardia)
Nitrogen Cycle
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Higher
plant
Precipitated
inorg.-P
issolved
org.-P
zooplankton
hytoplankton
bacteria
Dissolved
org.ortho-P
Sediment
Phosphorus Cycle
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R-SH H
2
S SO
4
2-
R-
SH
S
o
Dissimilatory
sulfate reduction
S
o
S
2
O
3
2-
R-SH
sulfate
assimilation
sulfate
assimilation
desulfurylation
Anaerobic
Aerobic
Chromatium
Chlorobium
Chromatium
Chlorobium
Beggiatoa
Thiothrix
Thiobacillus
some procaryotes)
Desulfovibrio
Sulfur Cycle
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•
Use light as E-source for CO2 fixation •
Photosynthetic bacteria fix CO2 by a reversal of
the TCA cycle
•
was discovered in 1966 in Chlorobium
thiosulfatophilum (green sulfur bact., anoxygenic)
• requires ATP, NADH + H+, reduced flavin, and
reduced ferredoxin
• ferredoxin is reduced in a light-dependent
reaction coupled with the oxidation of H2S
Photoautotroph
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• reduced ferredoxin serves as an electron donor
for the reduction of CO2 •
this cycle probably occurs as a sole pathway
for CO2 fixation or in association with the
Calvin cycle
• photoorganotrops or photoheterotrophs use
light as an E-source and organic compound asC-source e.g. Rhodospirillaceae (purple non-
sulfur bact.)
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Use chemical compounds (NH3, NO2-, CH4, H2S,
H2) as E-source for CO2 fixation
are widely distributed in the natural environment
e.g. freshwater ponds and springs
soil
acid drainage water
Nitrifying
bacteria
Sulfur-oxidizing bacteria
(Thiobacillus thiooxidans
Thiobacillus ferrooxidans)
Chemoautotroph
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Heterotrophic CO2 fixation is an important way
for m.o. to synthesize intermediates of TCAcycle from other chemical compounds
Phosphoenolpyruvate + CO
2
oxaloacetate + P
i
ATP + pyruvate + CO
2
oxaloacetate + ADP + P
i
Oxaloacetate formed by either type of
mechanism is used to keep the TCA cycle
functioning
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Methanogens (Methanobacterium, Methanococcus ) can
anaerobically reduce CO2
to CH4
Methanogens are found in anaerobic habitats rich inorganic matter e.g. swamps, marine sediments,
intestinal tract and rumens of animals)
the amount of CO2 fixed by heterotrophs and
methanogens is quite small compare to
photoautotrophs
CO2 + 4H2 CH4 + 2H2O
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! A soil aggregate composed of mineral
and organic components
Profile of a mature soil
Mineral Soils: the weathering of rock,
Organic Soils: Sedimentation in bogs
and marshes
Soils are microbial habitats, water
availability limits microbial activity
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! they are responsible for many of the
biochemical changes in soil
! the most common soil bacteria : Arthrobacter,
Bacillus, Pseudomonas, Agrobacterium,
Alcaligenes, Flavobacterium, Streptomyces,
and Nocardia (Actinomyces)
Bacteria are the dominant m.o. in soil
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• obligate anaerobes such as Clostridium and
Desulfovibrio are also found in soil• soil bacteria are especially noted for their
diverse metabolisms because the organic
nutrients in soil vary
Pseudomonas
Different types
of CHO
Bacillus Starch, cellulose, gelatin
Arthrobacter Pesticides, caffeine,
phenol
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Role and activity of fungi
•
degrade organic matters• control growth of other organisms e.g.
Predator protozoa, nematode
•
humus formation
• improve soil aggregation
•
help in the nutrient adsorptionof plant root e.g. mycorrhiza
• cause disease in human, plants, and animals
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! eucaryotic algae and cyanobacteria are found
in the upper layers of soil
! algae do not require a source of organic
carbon because!????!
! light accessibility, N, and P are the limiting
factor in the distribution of algae
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Role and activity of algae
increase organic carbon in soil
CO2 org.-C
soil corrosion (from respiration product)
CO2 + H2O H2CO3
prevent soil erosion and improve soil
aggregation
nitrogen fixation blue-green algae
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! are found in greatest abundance near the soil
surface (104 -105 cells)
! why ?adequate food supply
water availability and
organic matter
• flagellated protozoa (e.g. Allantion , Bodo )
dominate the flora of terrestrial habitats
• soil can also be a reservoir for pathogenic
protozoa such as Entamoeba histolytica
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•
different types of viruses persist in soil
- Bacteriophages of soil bacteria
- viruses that cause human, animal, and
plant dieases e.g. hepatitis virus, tobacco
mosaic virus
- are of agricultural and public health
importance- the detection and monitoring of such
viruses in soil is important
Virus
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rhizosphere = the region of soil closely
surrounding the roots
rhizosphere effect = a consequence of the
excretion of organic matter by plant roots to
attract and stimulate the growth of soil bacteria
an estimated 5-10 times more nitrogen is fixed
symbiotically than nonsymbiotically in free-living
bacteria
Nitrogen FixationSymbiotic: Rhizobium, Bradyrhizobium
Non-Symbiotic/free-living: Azospirillum, Azotobacter,Rhodospirillum, Rhodobacter, Clorobium
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N2+8H++8e-+16MgATP 2NH3+H2+16 MgADP+16Pi
Nitrogenase
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the mutualistic association between rhizobia
(Rhizobium or Bradyrhizobium) and legumes is
highly specific
The plant benefits from the bacterial conversion of
gaseous N into a usable combined form
the plant provides the bacterium with nutrient for
growth and metabolism
N-fixation occurs only if a legume is infected by a
specific rhizobial species
the roots of leguminous plant secrete flavonoid
compounds that attract rhizobia to rhizosphere
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Leaching : is commercially used for theextraction of Cu, Pb, Zn, and Ur from sulfide-
containing ores
Thiobacillus thiooxidans andThiobacillusferrooxidans are acidophilic and generally
found in acid environments e.g. hot springs
and sulfide ore deposits
they obtain carbon from CO2 and energy for
growth from the oxidation of either iron or
sulfur
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Fe2+ Fe3+
So S2-
S2O32-
SO42-
Acid mine drainage serious problem
FeS2 + H2SO4 + 1/2 O2 FeSO4 + 2 So + H2O
2 So + 2 H2O + 3 O2 2 H2SO4
Acidification of water
and surrounding soil
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Benefit : Microbial leaching in Copper mining
• low grade Cu ores contain
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• typical aquatic environments are the oceans,
estuaries, salt marshes, lakes, ponds, rivers,
and springs
• because aquatic environments differ considerably
in chemical and physical properties, so theirmicrobial species compositions also differ
Microbes and Water
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• saltwater organisms differ from freshwater
organisms based upon osmotic properties
• Algae (phytoplankton) are common in
marine habitats and provide significant
organic carbon
• the bacterial population in estuaries
consists of Pseudomonas, Flavobacterium,
and Vibrio , as well as enteric organisms
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• the numbers and types of bacteria in water
depend on the physical parameter ofwater -- salinity, temperature, dissolved
oxygen, and pH
•
freshwater habitats contain a wide variety ofmicroorganisms
• Rivers may contain large numbers
of soil bacteria (Bacillus, Actinomyces ), fungi
(Penicillium, Aspergillus ), and algae
(Microcystis, Nostoc )
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! Rivers also receive high concentration of
bacteria and agricultural chemicals through
surface runoff water
! Rivers can be polluted with sewage bacteria
esp. E. coli, Enterococcus faecalis, Proteus
vulgaris, Clostridium sp., and other intestinal
bacteria
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Lakes are relatively stagnant bodies of water
that can be divided into
- zone of light penetration
- temperature
Littoral zone
Limnetic zone
profundal zone
epilimnion hypolimnion
The microflora of a lake is determined by
lake’s nutrient content, thermal stratification,
and light compensation level
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Cyanobacteria and algae are abundant in the
littoral and limnetic zones
Photoautotrophic bacteria (Clorobium,
Rhodopeudomonas, and Chromatium ---- use
reduced org. and inorg. substanses as
e-donors) are found at lower depths
Chemolithotrophic bacteria (Nitrosomonas,
Nitrobacter, and Thiobacillus ) are also found
in freshwater bodies
The m.o in water frequently are the beginning
of food chain in aquatic environment
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Microorganisms are not found in the upperregions of the atmosphere because of the
temp. extremes, available oxygen, absence of
nutrients and moisture, and low atmospheric
pressures
m.o. are frequently found in the lower portion
of the troposphere (8-12 km from earth)
most of them are either spore formers or
microbes that are easily dispersed in the air
Microbes and The Air
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Ex. : Cladosporium, Alternaria, Penicillium,
Actinomyces, Aspergillus, Bacillus, Sarcina,
Corynebacterium, Achromobacter
the relative low humidity in the atmosphere
and UV rays from the sun limit the types and
number of m.o. in the air
Nevertheless, the atmosphere serves as an
important medium for dispersing many types of
microbes to new environmentmany microbial diseases are transmitted
through the air during sneezing, coughing, or
even normal breathing
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