EVSC Ch 1 & 2.Intro & Metobolism. 09[1]

7/30/2019 EVSC Ch 1 & 2.Intro & Metobolism. 09[1]

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1ESC 590Intro, Microbial Growth & Metabolism

Reading Assignment

Soil Microbiology:An exploratory

ApproachChapters 1 and 2


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1. Soil Microbiology

Soil microbiology is the study of organisms thatlive in the soil.

The main trust of study is on their metabolic and

their roles in energy flow and cycling of nutrientsassociated with primary productivity the energyflow and activities.

The discipline is also concerned with the

environmental impacts, both favorable andunfavorable, of soil microorganisms and the

processes the mediate.


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1. Soil Microbiology

Soil microbiology is concerned with

microbial communities in soil and what

they do. It uses a synecology approachprocess

oriented

Autoecology approach - uses more of anindividual approach.


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2. Soil Biochemistry

Traditionally biochemistry has been defined

as the chemistry that deals with life processes

of plants and animals. The scientific discipline of soil biochemistry

follows this tradition. Many of the reactions

the soil biochemist investigates result fromthe activities of living tissues, e.g.

microorganisms and plants.


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In addition, the study of soil organic matter

its origin and biochemical reactivities, are

also included in the domain of soilbiochemistry even though these may no

longer be in association with any living

system.


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In 1946 J.H. Quastel proposed that the soil

as a whole can be considered an organ

comparable in some respect to a liver or agland to which may be added various

nutrients, pure or complex degraded plant

materials, rain, air and in which enzymatic

reactions occur.


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The products of these reactions are

important steps in elemental cycles, in the

percolation of iron and aluminum humates,in the formation of soil crumb structure, and

in other processes.


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The notion here is that the soil biochemist is

concerned more with what the microbes are

doing in the soil than with precisely whatthe microbes are with respect to size and

shape or the ingredients of taxonomic

schemes.


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In this course we will study soil

biochemistry using this concept which

views the soil as a tissue, containing manykinds of compounds, to which biochemical

principles can be applied.

Soil Cell Membrane


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3. Overview of Metabolism

Metabolism refers to all the chemical

processes that take place within a cell.

It is composed of two basic reactions:- A. Anabolism

- B. Catabolism

Anabolic reactions require energy tosynthesize complex molecules from simpler

ones.


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3. Overview of Metabolism

Catabolic reactions release energy by

braking complex molecules.

All catabolic reactions involve electrontransfer, which allows energy to be captured

in high energy bonds


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4. Microbial Nutrition

Nutrients

- Chemical tools needed to make monomers.

Essential Nutrients- C H,O, P,K,N, S, Ca, Fe, Mg,

Macronutrients

- Needed in large amounts

- Include C, H, O, P, S, K, Mg, Na, Ca, Fe


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4. Microbial Nutrition

Micronutrients (Trace Elements)

- Required in small amounts

- Mainly metals and play role in enzymes- Include Cr, Co, Mn, Mo, Ni, Se, W, V, Zn, Fe

Growth Factors

- Organic compounds required in very smallamounts and only by some cells.

- Include vitamins, amino acids, and nucleotides .


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Culture Media

Culture media are nutrients solutions used

to grow microorganisms.

Two broad classes- A. Chemically defined-prepared by adding

precise amounts of highly purified inorganic or

organic chemicals and distilled water.

- B. Undefined (complex)-These are made up of

digest of casein, beef, soybean, yeast cells other

highly nutritious substances.


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5. Energy Classes of Microorganisms

One of the fundamental properties of living

organisms is their requirement of energy.

Phototrophs, meet their energy requirements

by absorption of a quanta of solar radiation.

Chemotrophs obtain energy needs by

oxidation of preformed organic molecules.


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Characterization of Metabolic

Reactions Based on Electron

Donors/Acceptors

Class Electron Donor Electron AcceptorPhotoautotrophic

(Photolithotroph) H2O, H

2S, H

2R CO

2

Respiration

(organothrops) Organic Compounds O2


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Biological Oxidations

Biological oxidations reactions are

frequently dehydrogenation reactions.

Biological oxidation reactions almostalways involve two electron transfers.

In chemotrophic energy metabolism the

ultimate energy acceptor of electrons isfrequently oxygen.


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The electrons are generally passed to the

final electron acceptor through intermediate

electrons acceptors In most biological oxidations, the

immediate electron acceptor is one of

several coenzymes-specialized moleculesthat function specifically as carriers of

electrons.



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The most common coenzymes are NAD+,

NADP+ and FAD

Aerobic energy metabolism involvesstepwise process collectively called

respiration.

Under anaerobic conditions, oxygen is not

available as electron acceptor, and the

electrons are passed instead to some organic

or inorganic molecule .


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All anaerobic processes are called

fermentations and they are usually further

identified in terms of the principal end

product i.e. the reduced form of the organic or

inorganic electron acceptor.


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6. Oxygen Requirements

Organisms with an absolute requirement for

oxygen arestrict or obligate aerobes.

- Most higher animals are in this category. Strict or Obligate anaerobes cannot tolerate

the presence of oxygen.

- Some bacteria , including soil Clostridia andthose responsible for denitrification are found

in this category


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6. Oxygen Requirements

Facultative organisms are those which can

exist anaerobically, extracting energy from

glucose (or other organic substrates) byfermentative processes, but which can also

function in the presence of oxygen, in

which case they carry out the fullrespiratory sequence.


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7. Methods of Metabolism

All classes of energy yielding reactions can

be classed under four main groups:

1. Respiration2. Fermentative reactions

3. Chemoautotrophic reactions.

4. Photosynthetic


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7.1a Aerobic Respiration

Aerobic Respiration is properly defined as

the oxidation of organic molecules with

molecular oxygen serving as the ultimateelectron acceptor.

The result of aerobic respiration is the

complete degradation of organic molecules

to the products, CO2 and H2O.


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7.1b Anaerobic Respiration

Anaerobic Respiration is a variation of

respiration in which electron acceptors other

than oxygen are used. Electron acceptors used include NO3

-, Fe3+ ,

SO4-, CO3

-

Under anaerobic respiration, less energy isreleased compared to aerobic respiration.


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7.1 Aerobic vs. Anaerobic

Respiration

Class Electron Donor Electron Acceptor

AerobicRespiration Organic Compounds O2

Anaerobic Respiration Organic Compounds Inorganiccompound


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7.2 Fermentation Reactions

In fermentation reactions, organic molecules

are oxidized with the electrons being given to

electron acceptors other than O2.

One common fact concerning each of the

classes of fermentation is that the source of

electrons involved is organic compounds.


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Comparision of Fermentation, Aerobic

Respiration, and Anaerobic Respiration.

Energy-Producing Process Growth Conditions

Fermentation Aerobic or anaerobic

Aerobic respiration Aerobic

Anaerobic respiration Anaerobic


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7.2 Fermentation Reactions

The distinguishing feature of the

fermentative reactions, however is the

nature of the electron acceptors and the

products formed.

The yield of energy obtained from a

fermentative reaction is much less

compared to that of respiration contained in

a given substance.


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7.2. Fermentation Reactions

Class Electron Donor Electron Acceptor

Heterofermentative Organic Compounds Same molecule or

fragment of it.

Multifermentative Organic Compounds Different organic

compound or CO

2

Isofermentative Organic Compounds Another molecule

of substrate


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Comparison of Fermentation,

Aerobic and Anaerobic Respiration.

Energy-

Producing

Process

Growth

Conditions

Final Electron

Acceptor

Type of

Phosphorylation

used to build ATP

Molecules

of ATP

Produced

Fermentation Aerobic oranaerobic

An organic molecule Substrate-level 2

Aerobic

respiration

Aerobic Free oxygen (O2) Substrate-level and

oxidative

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Anaerobic

respiration

Anaerobic Usually an inorganic

substance (such as

NO3-, SO42-, CO3

2- ),

but not free oxygen

(O2).

Oxidative Variable


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7.3. Chemolithotrophic Metabolism

In this mode of energy generation,

organisms use inorganic chemicals as

electron donors. It usually involves aerobic respiratory

processes but uses an inorganic energy

source rather than an organic one. Examples inorganic electron donors include

H2S, H2, Fe2+ and NH3.

Class Electron Donor Electron Acceptor Products


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Photoautotrophic

(Photolitotroph)

H2O, H2S, H2R CO2 (HCHO)x and other reduced

compounds

Respiration

(Heterotrophs)

Organic Compounds O2 CO2 + H2O

Homofermentative Organic Compounds Same molecule or fragment

of it

Single organic species + CO2 in some

cases

Heterofermentative Organic Compounds Same molecule or fragment

of it.

Mixture of organic compounds

Multifermentative Organic Compounds Different organic

compound or CO2

Organic compounds

Isofermentative Organic Compounds Another molecule of

substrate

Reduced organic compound and

Oxidized organic compound

Anerobic Respiration Organic Compounds Inorganic compound Organic Compound or CO2 + H2O:

more reduced inorganic compound

Chemoautotrophic

(Chemolitotroph)

Inorganic Compounds O2 or another inorganic

compound

Oxidized inorganic compound


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7.4 Photosynthetic Reactions

Photosynthesis may be defined as a series of

reactions which utilize solar energy to

convert CO2 into cellular components. It isimportant both to the carbon and oxygen

cycle.

It is also the chemical source of oxygenwhich is absolutely required by aerobic

organisms.


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EVSC Ch 1 & 2.Intro & Metobolism. 09[1]

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Transcript of EVSC Ch 1 & 2.Intro & Metobolism. 09[1]