10 Ekosistem Mikroba 2015

8/16/2019 10 Ekosistem Mikroba 2015

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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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10 Ekosistem Mikroba 2015