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Foundations in Microbiology

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Presentation on theme: "Foundations in Microbiology"— Presentation transcript:

1 Foundations in Microbiology
PowerPoint to accompany Foundations in Microbiology Fifth Edition Talaro Chapter 7 Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2 Elements of Microbial Nutrition, Ecology and Growth Chapter 7

3 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

4 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 (CH4), carbohydrates, lipids, proteins, and nucleic acids

5 Chemical composition of cytoplasm
70% water proteins 96% of cell is composed of 6 elements Carbon Hydrogen Oxygen Phosphorous Sulfur

6 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

7 Nitrogen 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.

8 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 O2 makes up 20% of atmosphere essential to metabolism of many organisms

9 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 oxidation-reduction reactions of respiration

10 Phosphorous 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)

11 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

12 Important mineral ions
Potassium Sodium Calcium Magnesium Iron

13 Growth factors organic compounds that cannot be synthesized by an organism & must be provided as a nutrient essential amino acids, vitamins

14 Carbon source Energy source photoautotrophs CO2 sunlight chemoautotrophs Simple inorganic chemicals photoheterotrophs organic chemoheterotrophs Metabolizing organic cpds

15 Saprobes – decompose dead organisms, recycle elements, release enzymes to digest materials
Parasites – utilize tissues and fluids of a living host and cause harm

16 saprobes

17 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

18 diffusion

19 osmosis


21 passive transport

22 Active transport

23 Bulk transport

24 Environmental influences on microbial growth
temperature oxygen requirements pH electromagnetic radiation barometric pressure

25 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

26 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

27 3 temperature adaptation groups

28 Oxygen requirements


30 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

31 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

32 Binary Fission

33 Population growth

34 Growth curve

35 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

36 Turbidity

37 Direct microscopic count

38 Electronic counting

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