Bacterial Growth, Genetics Chemothpy Lecture 3

8/2/2019 Bacterial Growth, Genetics Chemothpy Lecture 3

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MICROBIAL METABOLISM


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Composition of Bacteria

90% water

typical composition of the other 10%:

Hydrogen - 10-20%Nitrogen, Oxygen, Phosphorus - 10% each

Sulfur - 5%

Assorted ions: Na+, K+, Ca+2, Mg+2, Mn+2, Mo+2,

Zn+2, Fe+3

All of these must be obtained from the environment of

the cell

Carbon - 40-50%

Nitrogen, Oxygen, Phosphorus - 10% eachHydrogen - 10-20%Nitrogen, Oxygen, Phosphorus - 10% each


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Composition of Bacteria

Fe important that bacteria have developed specialIron-transporting systems called SIDEROPHOREScompete with human iron-chelators (lactoferrin,hemoglobin, myoglobin) to sequester iron for the

bacteriaSome bacterial infections are enhanced by high ironconditions

Humans will kill for gold and silver bacteria will killfor iron.

Some bacterial cytotoxins are produced only underconditions of iron deficiency.

(Ex. Diphtheria toxin)


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Characterization of Bacteria by Carbon SourceAutotrophs (self-feeders):

= obtain carbon from inorganic sources (CO2)

= obtain nitrogen from inorganic sources (NH4+, NO3

-)

Heterotrophs (fed by others):

= obtain carbon from organic sources

= obtain N2 from organic and/or inorganic sources

Medical bacteria are heterotrophs.


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Characterization of Bacteria by Energy SourcePhototrophs:

bacteria that obtain all their energy fromradiant energy (light = photosynthesis)

Photolithotrophs: use inorganic compounds as

electron donors and acceptors

Photoorganotrophs: use organic compounds aselectron donors and acceptors

Photolithotrophs = Autotrophs

Photoorganotrophs = Heterotrophs


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Characterization of Bacteria by Energy SourceChemotrophs:

bacteria that obtain all their energy from carryingout chemical reactions (not light-driven)

Chemoorganotrophs = Heterotrophs

Chemolithotrophs = Autotrophs

Chemolithotrophs: use inorganic compounds as electron

donors and acceptors

Chemoorganotrophs: use organic compounds as

electron donors and organic or inorganic acceptors


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BACTERIAL METABOLISM

METABOLISM= digestion & utilization of food to synthesize

CHO, fats, CHON, & other substances ---

living things are made to furnish the energynecessary for life & reproduction.

Two aspects:

ANABOLISM = building of protoplasm &storage of energy.

CATABOLISM = breaking of protoplasm &

release of energy.


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HOW BACTERIA TAKE IN THEIR FOODFood --- dissolved in H20 through process

of osmosis or diffusion

--- by the help of permease.

Glucose = occupies a greater importance in

the source of energy.


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FERMENTATION vs. RESPIRATION

Fermentation:

- energy (ATP)-yielding pathway in which

electrons are transferred from an organic donor

substrate (e.g., carbohydrate) to organic acceptors,forming organic acids, aldehydes, alcohols, etc.

The classic example is glycolysis:

lactateGlucose pyruvate acetate

ethanol

- anaerobic process


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FERMENTATION vs. RESPIRATION

Respiration:

- energy (ATP)-yielding pathway in which electrons aretransferred from an organic donor substrate

(e.g., carbohydrate) to inorganic acceptors via anelectron-transport chain (cytochromes, etc.)

The classic example is Ox/Phos:

BH2 + 0.5O2+ADP, Pi[cytochromes]

B +H2O + ATP

Acceptors other than O2 can be used:

NO3-, NO2

-, SO4

--, redox dyes, etc.


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PATHWAYS:

GLYCOLYTIC PATHWAY

- major route of glucose metabolism

- degrade glucose into 2 molecules of lactic acid

without molecular O2 intervention.- 47 kcal/mole fermented

a. EMBDENMEYERHOFFPARNAS SCHEME ( EMP )

- 4 molecules of ATP formed during glucosebreakdown

- initial reaction uses 2 molecules of ATP

- net yield of ATP = 2 molecules


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BACTERIAL METABOLISM PATHWAYS:

GLYCOLYTIC PATHWAY

b. PHOSPHOGLUCONATE PATHWAY

also: Hexosemonophosphate Shunt ( HMP )

- major energy pathway of heterolactic fermenters

- net ATP yield is half of EMP --- 1.

c. ENTNERDOUDOROFF PATHWAY

- utilize functional system for Pseudomonas

- net ATP = 1 ATP/mole of glucose fermentation ofCHO

- key intermediate product is pyruvic acid finalproduct to identify bacteria not only inindustrial establishment, also for paramedicalcourses.


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PYRUVIC ACID is degraded into the following products:

1. alcohol fermentation

pyruvic acid acetaldehyde & CO2

reduced ethyl ROH

value: brewing industry

2. homolactic fermentation

pyruvic acid lactic acid

decarboxylated

Lactobacilli/Streptobacilli


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3. Heterolactic acid pyruvic acid lactic acidformic acid

ROH

CO2

acetic acid

4. Propionic acid fermentation pyruvic acid- responsible for the characteristic taste & smell of

Swiss cheese


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5. Mixed acid

pyruvic acid mixed acid

(lactic a., oxaloacetic a., formic a.)

True among enteric bacteria

( + ) methyl red test ( acidity - basis )

e.g. Escherichia coli

6. Strickland fermentation

- fermentation of nitrogenous organic compound

degraded


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7. Butanediol fermentationVogues Proskauer test

pyruvic acid precursor of acetoin or acetyl ROH

carbinol (neutral) 2, 3 butanediol

reaction: reversible in the presence of air

8. Butyric acid fermentation

Clostridia spp. ButanolIsopropanol end product

Acetone

Ethanol

reduced

reduced


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BACTERIAL METABOLISM AEROBIC RESPIRATION

= ultimate electron acceptor is molecular O2.

a. Krebs Cycle also: Citric acid cycle

Tricarboxylic acid cycle (TCA)

glycolytic glucose

pyruvic acid Krebs cycle

Energy yield: 686 kcal/mole

36 + 2 = 38 ATP yield

b. Glyoxylate cycle (modification of TCA cycle)

enter


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NUTRITION OF BACTERIAneed nutrients, Oxygen, pH, and Temperature

OXYGEN REQUIREMENT

Four Groups

1. Obligate Anaerobes grows only on high reducing intensity

- lacks catalase, peroxidase, superoxides

2. Facultative Anaerobes can grow under both aerobic andanaerobic conditions.

3. Obligate Aerobes can not grow unless oxygen is present

4. Microaerophilic organism can grow under condition of lowoxygen tension


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TEMPERATURE

Three groups:1. Psychrophilesbacteria grow in the range of 5-10o

with optimum of 10-20o

2. MesophilesBest grow at 20-45o

Most medically important bacteria belong here.

3. Thermophilesorganism prefer high temperatures.

pH Important for multiplication of bacteria Growth ranges from 3 to 4 Most pathogenic bacteria ranges from 7.2 7.6


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- with adequate nutrition bacterium enlarges bybinary fission forming two daughter cells

PARENT CELL

ELONGATION OF THE CELLCELL ENVELOPES GROW INWARDS

FORMATION OF TRANSVERSE WALL

SEPARATION OF CELL FORMING

2 DAUGHTER

BACTERIAL GROWTH


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BACTERIAL GROWTH CURVE

Lag phase

Log phase/exponential phase

Stationary phase

Decline phase

BACTERIAL GROWTH


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Bacterial Growth Cycle

Lag phase

- adaptation, maturation, no division yet

- synthesis of RNA, enzymes and other molecules occurs

Exponential phase(log phase or the logarithmic phase)

- a period characterized by cell doubling Stationary phase

- the growth rate slows as a result of nutrient depletion and

accumulation of toxic products

- a constant value as the rate of bacterial growth is equal to therate of bacterial death

Death phase

- bacteria run out of nutrients and die


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BACTERIAL GROWTH CURVE
http://upload.wikimedia.org/wikipedia/commons/c/c0/Bacterial_growth_en.svg


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MICROBIAL GENETICSDNA 2 purines:

Adenine & Guanine

2 pyrimidines:

Cytosine & Thymine

Each purine and pyrimidine are joined by

hydrogen bonds

Compatible pairs: Adenine (A) & Thymine (T)

Guanine (G) & Cytosine (C)


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GENETICS: Each DNA carries w/in molecules the message

that controls the activity of the cell DNA w/in cell are double helix

(1 strand copied it produce 1 single identicalstrand etc.)

Once DNA strand are transcribed it produce anRNA( result of complementary base pairing w/in

DNA called mRNA codes for 1 amino acidwhich reacts to a specific anticodonproducing tRNA )

( known as the carrier of amino acid )

MICROBIAL GENETICS


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MUTATION

Genetic change as a result of a mistake inreplication of DNA

Rate can be increased by the use of

1. mutagenic agents reacting with DNA

2. DNA replication

3. base pair substitutions

4. frame shift mutations5. nonsense mutation


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GENETIC TERMS

DNA REPLICATIONchromosomes makes copy of itself.

DNA & GENETIC CODES DNA determines the sequenceof amino acid in the manufacture of cellular protein

TRANSCRIPTION DNA copying into corresponding RNA

TRANSLATION process in w/c mRNA directs thesynthesis of a specific protein

GENETIC CODES the sequence of bases over thesequence of amino acid

CODONseries of 3 nucleotides in a nucleic acid thatcodes 1 specific amino acid

ANTICODON 3 nucleotides on a tRNA thatrecognized the codon of mRNA

STRUCTURAL GENES genes that codes for proteinsynthesis


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Chemotherapeutic Agents


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CHEMOTHERAPY = treatment of infection bymeans of a substance use to combat m.o.

PROPERTIES of an IDEAL ANTIBIOTIC:

1. Selective toxicity-- toxic to m.o. but not to the host

2. Bactericidal rather than bacteriostatic3. Effective against broad range of m.o.4. Not allergenic5. Remain active in the plasma, serum,

or presence of exudate6. Water soluble & stable


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MECHANISM of ACTION of ANTIBIOTICS:1. Interfere with the cell wall synthesis

2. Interfere with protein synthesis3. Interfere with nucleic acid metabolism4. Interfere with cell membrane function


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ANTIBIOTIC AFFECTING the CELL WALL1. Penicillin 2 kinds:

natural (Pen G)

semisynthetic

(cloxacillin, methicillin, ampicillin, nafcillin)Cephalosporins = resemble Penicillin

2. Bacitracin

3. Cycloserine4. Vancomycin


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ANTIBIOTIC AFFECTING the

CELL MEMBRANE FUNCTION

1. Polymyxin -- against Pseudomonas & Gram ( - )2. Polyenes -- antifungal

3. Amphothericin B -- Tx for deep seated fungi

4. Nystatin -- for superficial antifungal infection


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ANTIBIOTIC that INTERFERE DNA FUNCTION

1. Nalidixic acid

2. Novobiocin3. Griseofulvin


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