bacteriology physiology
TRANSCRIPT
Dr Saleh Microbiology 1
Bacterial Physiology
Medical Microbiology L3
Dr. Saleh M Y OTH
PhDMedical Molecular Biotechnology and Infectious Diseases
05/10/2011MBBS-Phase II-IMS - MSU
Dr Saleh Microbiology 2
Bacterial growth
Metabolism is the totality of an organism’s chemical
processes to maintain life
Dr Saleh Microbiology 3
Studying Bacterial Growth
Bacterial Growth - features
The Growth Curve
Bacterial Growth
Dr Saleh Microbiology 4
NUTRITION
What are nutrients that bacteria want?
Bacterial Growth
Dr Saleh Microbiology 5
Nutritional requirements:
1- Macroelements: a- C, N,O, H, S, P. Required in large
amounts; constitute 95% of bacterial cell dry weight,
b- K, Ca, Mg, and Fe found as ions.
Bacterial Growth
Dr Saleh Microbiology 6
Nutritional requirements:
2- Microelements: Mn, Zn, Co, Mo, Ni, Cu are required in trace amounts by most cells =are part of enzymes and cofactors.
3- Growth factors: (cannot synthesize by cell); amino acids, nucleotides (purines and pyrimidines), vitamins.
Bacterial Growth
Dr Saleh Microbiology 7
- Nutritional
- Environmental
- Pure culture
Culture of microorganisms
Culture media
Dependence on oxygen
- Bacterial growth in laboratory conditions
Growth curve
- Microbial metabolism
Factors for microbial growth: Bacterial Growth
Dr Saleh Microbiology 8
Required elements
- C, H, O sources (amino acids, lipids, nucleic acids, sugars)
- N source (amino acids and nucleic acids)
- S source (amino acids)
- P source (nucleic acids, membrane lipids, ATP)
- K, Mg, Ca, Fe (enzyme cofactors, etc.)
Growth factors
Compounds that bacteria require but cannot synthesize
Nutritional factors
Energy sources
-Sunlight for phototrophs
-Oxidation of chemical compounds for chemotrophs
Nutritional diversity (concerning the energy source and carbon source)
-Photoautotrophs
(primary producers)
-Photoheterotrophs
*Chemoautotrophs
*Chemoheterotrophs
Bacterial Growth
Dr Saleh Microbiology 9
1-Nitrogen source; Ammonium (NH4+) is used as the sole N source by most microorganisms. Ammonium could be produced from N2 by nitrogen fixation, or from reduction of nitrate and nitrite.
2-Sulfur source; Most microorganisms can use sulfate (SO4
2-) as the S source.
3-Phosphate source (PO43-) is usually
used as the P source.
Bacterial GrowthNutritional factors
Dr Saleh Microbiology 10
4-Mineral source; For most microorganisms, it is necessary to provide sources of K+, Mg2+, Ca2+, Fe2+, Na+ and Cl-. Many other minerals (e.g., Mn2+ , Mo2+, Co2+, Cu2+ and Zn2+) can be provided in tap water or as contaminants of other medium ingredients.
5-Growth factors; Compounds that bacteria require but cannot synthesize
Bacterial GrowthNutritional factors
Dr Saleh Microbiology 11
1-TemperaturePsychrophile (15oC - 20oC)
Mesophile (30oC - 37oC)
Thermophile (50oC - 60oC)
2-pHNeutrophile (pH 6 - 8)
Acidophile (pH 1-5)
Alkaliphile (pH 9-11)
Environmental factors
3-Oxygen availabilityObligate aerobe (O2)
Obligate anaerobe (CO2)
Facultative anaerobe (O2 /CO2)
Microaerophile (5-10% O2)
4-Water availabilityOsmophile
Halophile
Bacterial Growth
Dr Saleh Microbiology 12
Obligate aerobe
Facultative anaerobe
Obligate anaerobe
Microaerophile1
2
3
4O2
O2 or Co2
Co2Superoxide dismutase
Dr Saleh Microbiology 13
Obtaining a pure culture
A solid medium is required for
obtaining a pure culture of
microorganism.
Agar: an algae extract,
polysaccharide in nature, which
very few bacteria can degrade.
The agar plate contains 1.5%
of agar.
Colony: population of bacterial
cells arising from a single cell.
Cultivating bacteria on a solid medium (bacterial isolation)
Dr Saleh Microbiology 14
Dr Saleh Microbiology 15
Dr Saleh Microbiology 16
Streak-plate method
Dr Saleh Microbiology 17
Pour plate method
Dr Saleh Microbiology 18
Culture of microorganisms
Complex (rich) media
nutrient agar or broth;
blood agar or chocolate agar for more fastidious bacteria.
Chemically defined (minimal media)
Selective media
Inhibitors for organisms other than the one being sought are added.
Culture media Differential media
Substances that certain bacteria change in a recognizable way are added.
Nutrient broth Glucose-salt
Peptone Glucose
Meat extract Dipotassium phosphate
Water Monopotassiumphosphate
Magnesium sulfate
Ammonium sulfate
Calcium chloride
Iron sulfate
Water
Dr Saleh Microbiology 19
MacConkey agar plate
Blood agar plate
Back
Dr Saleh Microbiology 20
Principles of bacterial growth
-Bacteria multiply by
binary fission.
-Microbial growth is
defined as an increase in
the number of cells in a
population.
Bacterial growth curve
Bacterial growth in laboratory conditions
Generation time
E. coli: 20 min
M. tuberculosis: 12-24 h
Dr Saleh Microbiology 21
Bacterial growth curve
Bacterial growth in laboratory conditions
Dr Saleh Microbiology 22
A balance between slow loss of cells through death and the formation of new cells through growth and division.
Bacteria synthesize macromolecules required for multiplication.
The length of lag phase depends on the conditions in the original culture and the medium into which they are transferred.
The doubling time is measured during this period.
The bacteria are most susceptible to antibiotics during this time. Bacteria stop growing due to decrease of nutrients and O2 supply, and accumulation of toxic metabolites.
The bacteria die off rapidly, the curve turns downward, and the last cell in the population soon dies.
Dr Saleh Microbiology 23
Assimulation (anabolism): energy-requiring
Dissimulation (catabolism): energy-acquiring
Bacterial Metabolism
Focal metabolites: metabolic intermediates that link
anabolic and catabolic pathways.
Glycolysis
Pentose phosphate pathway
TCA cycle
Respiration (aerobic and anaerobic)
Fermentation
Dr Saleh Microbiology 24
Saccharomycetes
E. coliClostridium
Propionebacterium Enterobacter
StreptococcusLactobacillus
Dr Saleh Microbiology 25
Increased CO2
Candle jar; CO2 incubator
Microaerophilic
Culture methodsAnaerobic
Anaerobic jar; anaerobic chamber; reducing agents
Dr Saleh Microbiology 26
Enrichment culturesIsolating an organism from natural sources
Dr Saleh Microbiology 27
Maintaining stock cultures
Agar slant
Store agar slant cultures in a
refrigerator.
Stock at –70 to -80 oC
Store a pure culture in the
presence of 17% glycerol.
Lyophilization (freeze drying)
Dry a pure culture with a
lyophilizer. This can be stored
at room temperature for years.
Dr Saleh Microbiology 28
Direct cell count
Count under a microscope;
cell-counting instrument
Measuring biomass
Turbidity;
total weight;
chemical constituents
Viable cell count
Plate counts(MPN);
membrane filtration;
Detecting cell products
Methods to detect and measure bacterial growth
Dr Saleh Microbiology 29
Dr Saleh Microbiology 30
Overview of Medically Important Bacteria
Rickettsia Chlamydia Mycoplasma*
Clostridia
Actinomycetes
Obligate IntracellularExtracellular & Facultative
Gram-positive Gram-negative Mycobacteria Spirochetes
Cocci Bacilli
StaphylococciStreptococciEnterococci
ListeriaBacillusCorynebacteria
Cocci and coccobacilli
Bacilli
Haemophilus
Bordetella
Neisseria
Enterobacteriaceae
Pseudomonads
Legionella
Campylobacter
Helicobacter
Borrelia
Leptospira
Treponema
Brucella
Francisella
Pasteurella
Aerobes StrictAnaerobes
Vibrio
Dr Saleh Microbiology 31
Topics for reading:
Using of Microscope and its parts
Classification of Bacteria
Bacterial structure
Bacterial multiplication
Bacterial genetic
Dr Saleh Microbiology 32
Topics for reading:
Catabolism and anabolism
ATP Generation and energy conservation
Fermentation
Dr Saleh Microbiology 33
Thank you
Study QuestionsBesides chemical nutrients, what are 4 other factors you would consider when trying to grow a bacterium for the first time?
Why do you need to sterilize bacterial media? What are some ways you could do this? What would happen if you didn’t sterilize the media?
What are the four phases of growth curve? What is happening in each?