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 Micronutrients or trace elements required in small amounts; involved in enzyme function & maintenance of protein structure manganese, zinc, nickel 2 Nutrients 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 (CH 4 ), carbohydrates, lipids, proteins, and nucleic acids 3
Chemical composition of cytoplasm 70% water proteins 96% of cell is composed of 6 elements Carbon Hydrogen Oxygen Phosphorous Sulfur 4 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 CO 2, an inorganic gas as its carbon source not dependent on other living things 5 Nitrogen Main reservoir is nitrogen gas (N 2 ) 79% of earth s atmosphere is N 2 Nitrogen is part of the structure of proteins, DNA, RNA & ATP these are the primary source of N for heterotrophsh Some bacteria & algae use inorganic N nutrients (NO 3-, NO 2-, or NH 3 ) Some bacteria can fix N 2 Regardless of how N enters the cell, it must be converted to NH 3, the only form that can be combined with carbon to synthesis amino acids, etc. 6
Oxygen 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 O 2 makes up 20% of atmosphere essential to metabolism of many organisms 7 Hydrogen 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 oxidationreduction reactions of respiration 8 Phosphorous main inorganic source is phosphate (PO -3 4 ) derived from phosphoric acid (H 3 PO 4 ) found in rocks & oceanic mineral deposits key component of nucleic acids, essential to genetics serves in energy transfers (ATP) 9
Sulfur 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 10 Potassium Sodium Calcium Magnesium Iron Important mineral ions 11 Growth factors organic compounds that cannot be synthesized by an organism & must be provided as a nutrient essential amino acids, vitamins 12
Carbon source Energy source photoautotrophs CO 2 sunlight chemoautotrophs CO 2 Simple inorganic chemicals photoheterotrophs organic sunlight chemoheterotrophs organic Metabolizing organic cpds 13 Saprobes decompose dead organisms, recycle elements, release enzymes to digest materials Parasites utilize tissues and fluids of a living host and cause harm 14 saprobes 15
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 i 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 16 diffusion 17 osmosis 18
passive transport 19 Active transport 20 Bulk transport 21
Environmental influences on microbial growth temperature oxygen requirements ph electromagnetic radiation barometric pressure 22 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 23 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 24
3 temperature adaptation groups 25 Oxygen requirements 26 27
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 28 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 29 Binary Fission 30
Population growth 31 Growth curve 32 Growth curve 1. Lag phase flat period of adjustment, enlargement; little growth 2. Exponential growth phase a period of maximum growth will continue as long as cells have adequate nutrients & a favorable environment 3. Stationary phase rate of cell growth equals rate of cell death cause by depleted nutrients & O 2, excretion of organic acids & pollutants 4. Death phase as limiting factors intensify, cells die exponentially in their own wastes 33
Turbidity 34 Direct microscopic count 35 Electronic counting 36