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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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BACTERIAL METABOLISM
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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BACTERIAL METABOLISM
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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BACTERIAL METABOLISM
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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BACTERIAL METABOLISM
PYRUVIC ACID is degraded into the following products:
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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BACTERIAL METABOLISM
PYRUVIC ACID is degraded into the following products:
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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BACTERIAL METABOLISM
PYRUVIC ACID is degraded into the following products:
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.svg8/2/2019 Bacterial Growth, Genetics Chemothpy Lecture 3
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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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Chemotherapeutic Agents
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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Chemotherapeutic Agents
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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Chemotherapeutic Agents
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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Chemotherapeutic Agents
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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Chemotherapeutic Agents
ANTIBIOTIC that INTERFERE DNA FUNCTION
1. Nalidixic acid
2. Novobiocin3. Griseofulvin
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