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 (CH 4 ), 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 CO 2 Nitrogen – Fix N 2 or obtain as NO 3 -- NO 2 -, or NH 3 Oxygen – Atmospheric or dissolved in water Hydrogen – Minerals, water, organic compounds

Nutrient Sources - Continued Phosphorous – Mineral deposits Sulfur – Minerals, H 2 S 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 CO 2, 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 15 o C, capable of growth at 0 o C 2.Mesophiles – optimum temperature 20 o -40 o C, most human pathogens 3.Thermophiles – optimum temperature greater than 45 o C

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 CO 2 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