microbial nutrition and growth nutrition = obtaining required substances from the environment
TRANSCRIPT
Microbial Nutrition and Growth
Nutrition = Obtaining Required Substances from the
Environment
Essential Nutrients Must be Provided for an Organism to
Survive and Reproduce
Nutrients• Inorganic nutrients– atoms, ions or molecules
that contains a combination of atoms other than carbon and hydrogen– metals and their salts (magnesium sulfate, ferric
nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water
• Organic nutrients- contain carbon bonded to hydrogen and are usually the products of living things– methane (CH4), carbohydrates, lipids, proteins, and
nucleic acids
Macronutrients
• Required in Large Quantities
• Play principle roles in cell structure and metabolism
• Proteins (source of amino acids)
• Carbohydrates
Micronutrients
Needed in Small Amounts – like Minerals
Points about Bacterial Cytoplasm
• Mostly water
• Large proportion of protein
• 97% of dry weight is organic matter
• 96% of bacterial cell is composed of C, H, N, O, P and S
Challenge for Bacteria
How to get enough nutrients in forms that they can use to make
cell components
Bacteria Must Make
• Proteins
• Carbohydrates
• Lipids
• Nucleic Acids
Sources of Essential Nutrients
• Carbon – obtain in organic form, or reduce CO2
• Nitrogen – Fix N2 or obtain as NO3--
NO2-, or NH3
• Oxygen – Atmospheric or dissolved in water
• Hydrogen – Minerals, water, organic compounds
Nutrient Sources - Continued
• Phosphorous – Mineral deposits
• Sulfur – Minerals, H2S
• Metal Ions - Minerals
Mineral Nutrients Important in Microbial Metabolism
• Potassium – essential to protein synthesis and membrane function
• Sodium – used in some types of cell transport
• Calcium – cell wall and endospore stabilizer• Magnesium – component of chlorophyll;
membrane and ribosome stabilizer• Iron – component of proteins of cellular
respiration• Zinc, copper, nickel, manganese, etc.
Growth Factors
• Organic compounds that cannot be synthesized by an organism & must be provided as a nutrient– essential amino acids, vitamins
Nutritional Types
• Autotrophs - use CO2, an inorganic gas as carbon source
• Heterotrophs - obtain carbon in an organic form made by other living organisms
Autotrophs – “Self-Feeding”
• Phototrophs use light energy to reduce carbon or make ATP
• Chemotrophs use energy stored in inorganic chemical bonds to reduce carbon or make ATP
Heterotrophs
• Obtain reduced carbon compounds made by another organism
• Chemoheterotrophs – oxidize reduced carbon to make ATP
Two Kinds of Bacterial Heterotrophs
• Saprobes – Obtain nutrients from dead, decaying matter
• Parasites – Feed off a host organism
Environmental Influences on Microbial Growth
• Temperature
• Oxygen requirements
• pH
• Barometric pressure
3 Cardinal Temperatures
• Minimum temperature
• Maximum temperature
• Optimum temperature
3 Temperature Adaptation Groups
1. Psychrophiles – optimum temperature below 15oC, capable of growth at 0oC
2. Mesophiles – optimum temperature 20o-40oC, most human pathogens
3. Thermophiles – optimum temperature greater than 45oC
Ecological Groups by Temperature of Adaptation
Oxygen in the Microbial Environment
• Oxygen required by aerobic species (Bacillus, Pseudomonas) but produces toxic by-products; these species have efficient de-tox enzymes
• Facultative anaerobes can exist in presence of oxygen but have no requirement for it (E. coli, Staphylococcus, etc.)
Anaerobes – no Need for Oxygen
• Strict anaerobes cannot tolerate oxygen (Clostridium sp.)
• Aerotolerant anaerobes have atypical oxygen detox systems (Lactobacillus sp.)
• Capnophiles require higher CO2 pressures (Neisseria, Brucella, S. pneumoniae)
pH Effects on Growth
• Acidophiles require low pH (Thermoplasma)
• Alkalinophiles require high pH (Proteus)
Osmotic Effects
• Most microbes exist under hypotonic or isotonic conditions
• Halophiles – require a high concentration of salt
• Osmotolerant – do not require high concentration of solute but can tolerate it when it occurs
Miscellaneous Environmental Factors
• Barophiles require high environmental pressure (like deep sea Archae)
• Dehydrated Cell Stages – Spores
• Extreme radiation conditions - Dinococcus radiodurans
Ecological Relationships
• Symbiosis – existing together
• Mutualism – both parties benefit
• Commensalism – one party benefits without impacting the other
• Parasitism – one party benefits at expense of the other
• Synergism – multiple organisms working together
Microbial Biofilms
• Biofilms result when organisms attach to a substrate by some form of extracellular matrix that binds them together in complex organized layers
• Dominate the structure of most natural environments on earth
• Microorganisms communicate and cooperate in the formation and function of biofilms – quorum sensing
Ecological Relationships - Continued
• Antagonism – one party acts to inhibit or eliminate the other
• Example of antagonism:
Antibiosis – producing substances toxic to other organisms
Microbial Growth
Growth of a population at an exponential rate under optimal
conditions
Stages in Normal Growth
• Lag phase
• Exponential/log phase
• Stationary phase
• Death or decline
Mathematics of Population Growth
Growth Curve
Methods for Monitoring Growth
• Dilution Plating
• Turbidity analysis using spectrophotometer
• Direct count with hemacytometer
• Optical detection – Coulter Counter
Turbidity
Direct Microscopic Count
Electronic Counting
It is Ideal to Perform Most Manipulations of a Culture When
it is Growing in Log Phase