elements of microbial nutrition ecology and growth chapter 7 n.
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Elements of Microbial Nutrition, Ecology and Growth Chapter 7

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Elements of Microbial Nutrition, Ecology and Growth Chapter 7. Microbial nutrition. Macronutrients – required in large quantities; play principal roles in cell structure & metabolism proteins, carbohydrates

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microbial nutrition
Microbial nutrition
  • Macronutrients – required in large quantities; play principal roles in cell structure & metabolism
    • proteins, carbohydrates
  • Micronutrientsor trace elements – required in small amounts; involved in enzyme function & maintenance of protein structure
    • manganese, zinc, nickel
  • Inorganic nutrients– atom or molecule 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 and hydrogen atoms and are usually the products of living things
    • methane (CH4), carbohydrates, lipids, proteins, and nucleic acids
chemical composition of cytoplasm
Chemical composition of cytoplasm
  • 70% water
  • proteins
  • 96% of cell is composed of 6 elements
    • Carbon
    • Hydrogen
    • Oxygen
    • Phosphorous
    • Sulfur
obtaining carbon
Obtaining Carbon
  • Heterotroph – an organism that must obtain carbon in an organic form made by other living organisms such as proteins, carbohydrates, lipids and nucleic acids
  • Autotroph - an organism that uses CO2, an inorganic gas as its carbon source
    • not dependent on other living things
  • Main reservoir is nitrogen gas (N2)
  • 79% of earth’s atmosphere is N2
  • Nitrogen is part of the structure of proteins, DNA, RNA & ATP – these are the primary source of N for heterotrophs
  • Some bacteria & algae use inorganic N nutrients (NO3-, NO2-, or NH3)
  • Some bacteria can fix N2
  • Regardless of how N enters the cell, it must be converted to NH3, the only form that can be combined with carbon to synthesis amino acids, etc.
  • major component of carbohydrates, lipids and proteins
  • plays an important role in structural & enzymatic functions of cell
  • component of inorganic salts (sulfates, phosphates, nitrates) & water
  • O2 makes up 20% of atmosphere
  • essential to metabolism of many organisms
  • major element in all organic compounds & several inorganic ones (water, salts & gases)
  • gases are produced & used by microbes
  • roles of hydrogen
    • maintaining pH
    • forming H bonds between molecules
    • serving as the source of free energy in oxidation-reduction reactions of respiration
  • main inorganic source is phosphate (PO4-3) derived from phosphoric acid (H3PO4) found in rocks & oceanic mineral deposits
  • key component of nucleic acids, essential to genetics
  • serves in energy transfers (ATP)
  • widely distributed in environment, rocks, sediments contain sulfate, sulfides, hydrogen sulfide gas and sulfur
  • essential component of some vitamins and the amino acids: methionine & cysteine
  • contributes to stability of proteins by forming disulfide bonds
important mineral ions
Important mineral ions
  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Iron
growth factors
Growth factors
  • organic compounds that cannot be synthesized by an organism & must be provided as a nutrient
    • essential amino acids, vitamins
Saprobes – decompose dead organisms, recycle elements, release enzymes to digest materials
  • Parasites – utilize tissues and fluids of a living host and cause harm
transport mechanisms
Transport mechanisms
  • Passive transport –do not require energy, substances exist in a gradient and move from areas of higher concentration towards areas of lower concentration
    • Diffusion
    • Osmosis - water
    • Facilitated diffusion – requires a carrier
  • Active transport – require energy and carrier proteins, gradient independent
    • Carrier-mediated active transport
    • Group translocation – transported molecule chemically altered
    • Bulk transport – endocytosis, exocytosis, pinocytosis
environmental influences on microbial growth
Environmental influences on microbial growth
  • temperature
  • oxygen requirements
  • pH
  • electromagnetic radiation
  • barometric pressure
3 cardinal temperatures
3 cardinal temperatures
  • Minimum temperature – lowest temperature that permits a microbe’s growth and metabolism
  • Maximum temperature – highest temperature that permits a microbe’s growth and metabolism
  • Optimum temperature – promotes the fastest rate of growth and metabolism
3 temperature adaptation groups
3 temperature adaptation groups
  • Psychrophiles – optimum temperature below 15oC, capable of growth at 0oC
  • Mesophiles – optimum temperature 20o-40oC, most human pathogens
  • Thermophiles – optimum temperature greater than 45oC
microbial associations
Microbial associations
  • Symbiotic – organisms live in close nutritional relationships; required by one or both members
    • Mutualism – obligatory, dependent; both members benefit
    • Commensalism – commensal member benefits, other member not harmed
    • Parasitism – parasite is dependent and benefits; host is harmed
microbial associations1
Microbial associations
  • Non-symbiotic – organisms are free-living; relationships not required for survival
    • Synergism – members cooperate and share nutrients
    • Antagonism – some member are inhibited or destroyed by others
growth curve1
Growth curve
  • Lag phase – “flat” period of adjustment, enlargement; little growth
  • Exponential growth phase – a period of maximum growth will continue as long as cells have adequate nutrients & a favorable environment
  • Stationary phase – rate of cell growth equals rate of cell death cause by depleted nutrients & O2, excretion of organic acids & pollutants
  • Death phase – as limiting factors intensify, cells die exponentially in their own wastes