Chapter 7: Microbial Nutrition, Ecology, and Growth PDF

Chapter 7 Microbial Nutrition, Ecology and Growth Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. © McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or fur...

Chapter 7 Microbial Nutrition, Ecology and Growth Lecture Outline See separate PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes. © McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted without the prior written consent of McGraw-Hill Education.  Microbial Nutrition Process by which chemical compounds (nutrients) are acquired from the environment to sustain life Bioelements – basic requirements for life (carbon, hydrogen, oxygen, phosphorus, potassium, nitrogen, sulfur, calcium, iron, sodium, chlorine, magnesium) – also called essential nutrients – body needs it and big amount! Essential nutrients – substance (element or compound) an organism must get from a source outside its cells- body can’t make them for itself. You need to get in through your diet. – Macronutrients – required in large quantities; play principal roles in cell structure and metabolism (proteins, carbohydrates) – a lot – Micronutrients or trace elements – required in small amounts; involved in enzyme function and maintenance of protein structure (manganese, zinc, nickel) – not that much 7-2 © McGraw-Hill Education.  Energy Extraction of Microorganisms Microorganisms get Their nutrients from The environment around Them. (photo, top left): © Kathy Talaro 7-3 © McGraw-Hill Education.  Nutrients Organic nutrients – contain carbon and hydrogen atoms and are usually the products of living things – CARBON, OXYGEN AND HYDROGEN. – carbohydrates, lipids, proteins, and nucleic acids. Inorganic nutrients – atom or molecule that contains a combination of atoms other than carbon and hydrogen _ Don’t have carbon, hydrogen and oxygen together. It can have anything, but those three. – Metals and their salts (magnesium sulfate, ferric nitrate, sodium phosphate), gases (oxygen, carbon dioxide) and water 7-4 © McGraw-Hill Education. Chemical Analysis of Cell Contents 70% water – mostly of what’s in a cell is water. 97% of dry cell weight is organic compounds: – Proteins the most prevalent 96% of cell is composed of 6 elements: – Carbon – Hydrogen – Oxygen – Phosphorous – Sulfur – Nitrogen 7-5 © McGraw-Hill Education.  Essential Biological Nutrients (1 of 17) TABLE 7.1 Sources and Biological Functions of Essential Elements and Nutrients 1) Carbon – anything that’s alive has Carbon. Fundamental for life! Elements/Nutrients Forms Found in Nature: CO2 carbon dioxide  gas CO3 2 carbonate Organic compounds Sources/Reservoirs of Compounds: – Air (0.036%*) – Sediments/Soils – Living Things 7-6 © McGraw-Hill Education.  Essential Biological Nutrients (2 of 17) The “TABLE 7.1” continues on this slide. Significance to cells: CO2 is produced by respiration and used in photosynthesis; CO32- is found in cell walls and skeletons (what makes skeleton strong); organic compounds are essential to the structure and function of all organisms and viruses. 2) Nitrogen Elements/Nutrients Forms Found in Nature: N2 gas NO3 nitrate  NO2 nitrate  NH3 ammonium Organic nitrogen proteins, nucleic acids 7-7 © McGraw-Hill Education.  Essential Biological Nutrients (3 of 17) The “TABLE 7.1” continues on this slide. Sources/Reservoirs of Compounds: – Air (79%*) – Soil and water – Soil and water – Soil and water – Organisms 7-8 © McGraw-Hill Education.  Essential Biological Nutrients (4 of 17) The “TABLE 7.1” continues on this slide. Significance to cells: Nitrogen gas is available only to certain microbes that fix it into other inorganic nitrogen compounds—nitrates, nitrites, and ammonium—the primary sources of nitrogen for algae, plants, and the majority of bacteria; animals and protozoa require organic nitrogen; all organisms use NH3 to synthesize amino acids and nucleic acids. 7-9 © McGraw-Hill Education.  Essential Biological Nutrients (5 of 17) The “TABLE 7.1” continues on this slide. 3) Oxygen Elements/Nutrients Forms Found in Nature: O2 gas Oxides H2O Sources/Reservoirs of Compounds: – Air (20%*), a major product of photosynthesis – Soil 7-10 © McGraw-Hill Education.  Essential Biological Nutrients (6 of 17) The “TABLE 7.1” continues on this slide. Significance to cells: Oxygen gas is necessary for the metabolism of nutrients by aerobes. Oxygen is a significant element in organic compounds and inorganic compounds (see water, sulfates, phosphates, nitrates, carbon dioxide in this table). -oxygen is necessary for metabolism. 7-11 © McGraw-Hill Education.  Essential Biological Nutrients (7 of 17) The “TABLE 7.1” continues on this slide. 4) Hydrogen Elements/Nutrients Forms Found in Nature: H2 gas H2O H2S hydrogen sulfide CH4 methane Organic compounds Sources/Reservoirs of Compounds: – Waters, swamps, mud – Volcanoes, vents – Swamps – organisms 7-12 © McGraw-Hill Education.  Essential Biological Nutrients (8 of 17) The “TABLE 7.1” continues on this slide. Significance to cells: Water is the most abundant compound in cells and a solvent for metabolic reactions; H2 , H2S, and CH4 gases are produced and used by bacteria and archaea; H+ ions are the basis for transfers of cellular energy and help maintain the pH of cells. 5) Phosphorus Elements/Nutrients Forms Found in Nature: PO4 3 phosphate 7-13 © McGraw-Hill Education.  Essential Biological Nutrients (9 of 17) The “TABLE 7.1” continues on this slide. Sources/Reservoirs of Compounds: – Rocks, mineral deposits – Soil Significance to cells: Phosphate, a key component of DNA and RNA, is critical to the genetic makeup of cells and viruses; also found in ATP and NAD, where it takes part in numerous metabolic reactions; its presence in phospholipids provides stability to cell membranes. 7-14 © McGraw-Hill Education.  Essential Biological Nutrients (10 of 17) The “TABLE 7.1” continues on this slide. 6) Sulfur Elements/Nutrients Forms Found in Nature: S SO 4 sulphate 2 SH sulfhydryl Sources/Reservoirs of Compounds: – Mineral deposits volcanic sediments – Soil 7-15 © McGraw-Hill Education.  Essential Biological Nutrients (11 of 17) The “TABLE 7.1” continues on this slide. Significance to cells: Elemental sulfur (S) is oxidized by some bacteria as an energy source; sulfur is found in vitamin B1; sulfhydryl groups are part of certain amino acids, where they form disulfide bonds that shape and stabilize proteins. 7) Potassium Elements/Nutrients Forms Found in Nature: K  Sources/Reservoirs of Compounds: – Mineral deposits, ocean water, soil Significance to cells: Plays a role in protein synthesis and membrane transport 7-16 © McGraw-Hill Education.  Essential Biological Nutrients (12 of 17) The “TABLE 7.1” continues on this slide. 8) Sodium Elements/Nutrients Forms Found in Nature: Na Sources/Reservoirs of Compounds: – Same as potassium Significance to cells: Major participant in membrane actions; maintains osmotic pressure in cells. 9) Calcium Elements/Nutrients Forms Found in Nature: Ca 7-17 © McGraw-Hill Education.  Essential Biological Nutrients (13 of 17) The “TABLE 7.1” continues on this slide. Sources/Reservoirs of Compounds: – Oceanic sediments, rocks, and soil Significance to cells: A component of protozoan shells (as CaCO3); stabilizes cell walls; adds resistance to bacterial endospores 10) Magnesium Elements/Nutrients Forms Found in Nature: Mg2  Sources/Reservoirs of Compounds: – Geologic sediments, rocks, and soil 7-18 © McGraw-Hill Education.  Essential Biological Nutrients (14 of 17) The “TABLE 7.1” continues on this slide. Significance to cells: A central atom in the chlorophyll molecule; required for function of membranes, ribosomes, and some enzymes 11) Chloride Elements/Nutrients Forms Found in Nature: Cl Sources/Reservoirs of Compounds: – Ocean water, salt lakes Significance to cells: May function in membrane transport; required by obligate halophiles to regulate osmotic pressure 7-19 © McGraw-Hill Education.  Essential Biological Nutrients (15 of 17) The “TABLE 7.1” continues on this slide. 12) Zinc Elements/Nutrients Forms Found in Nature: Zn2  Sources/Reservoirs of Compounds: – Rocks, Soil Significance to cells: An enzyme cofactor, regulates eukaryotic genetics 13) Iron Elements/Nutrients Forms Found in Nature: Fe 2  7-20 © McGraw-Hill Education.  Essential Biological Nutrients (16 of 17) The “TABLE 7.1” continues on this slide. Sources/Reservoirs of Compounds: – Rocks, Soil Significance to cells: Essential element for the structure of respiratory proteins (cytochromes) 14) Micronutrients Elements/Nutrients Forms Found in Nature: copper, cobalt, nickel, molybdenum, manganese, iodine Sources/Reservoirs of Compounds: – Geologic sediments, soil 7-21 © McGraw-Hill Education.  Essential Biological Nutrients (17 of 17) The “TABLE 7.1” continues on this slide. Significance to cells: Required in tiny amounts to serve as cofactors in specialized enzyme systems of some microbes but not all * As a portion of the earth’s atmosphere. 7-22 © McGraw-Hill Education.  Sources of Essential Nutrients: Carbon-Based Sources of the element carbon defines two basic nutritional types: you determine them depending on where they get their Carbon from. Heterotroph – must obtain carbon in an organic form such as proteins, carbohydrates, lipids, and nucleic acids made by other living organisms. (humans are heterotrophs because we life off of animals, plants, etc.) Autotroph – an organism that uses CO2, an inorganic gas, as its carbon source. Not dependent on a living thing. - they need carbon, but they get it from Carbon dioxide and that’s it. – Not nutritionally dependent on other living things 7-23 © McGraw-Hill Education. Growth Factors: Essential Organic Nutrients Organic compounds that cannot be synthesized by an organism because they lack the genetic and metabolic mechanisms to synthesize them Growth factors must be provided as a nutrient for survival – Essential amino acids, vitamins 7-24 © McGraw-Hill Education.  Classification of Nutritional Types Main determinants of nutritional type are: – Carbon source  Heterotroph – from other organisms  Autotroph – uses CO2 as source – Energy source  Chemotroph – gain energy from chemical compounds. (we get energy from glucose)  Phototrophs – gain energy through photosynthesis (from light). 7-25 © McGraw-Hill Education.  Nutritional Categories TABLE 7.2 Nutritional Categories of Microbes by Energy and Carbon Source Category / Carbon Energy Source Example Source Autotroph/CO2 Nonliving Environment Photosynthetic organisms, such as algae, Photoautotroph Sunlight plants, cyanobacteria Only certain bacteria and archaea, such as Chemoautotroph Simple inorganic chemicals methanogens and deep-sea vent bacteria Heterotroph/ Other Organisms Organic Carbon or Sunlight Metabolic conversion of the Chemoheterotroph nutrients from other Protozoa, fungi, many bacteria, animals organisms Metabolize the organic matter from dead organisms. Cleaning 1. Saprobe Fungi, bacteria, some protozoa (decomposers) up the planet to make nutrients. Obtain organic matter from Parasites, commensals, mutualistic 2. Symbiotic microbes living organisms microbes Photoheterotroph Sunlight or organic matter Purple and green photosynthetic bacteria 7-26 © McGraw-Hill Education. Autotrophs and Their Energy Sources (1 of 3) Photoautotrophs – Oxygenic photosynthesis (plants, algae, and cyanobacteria)  Produce oxygen and use chlorophyll as the primary pigment – Anoxygenic photosynthesis (purple and green sulfur bacteria)  no oxygen but sulfur production, use bacteriochlorophyl as pigment 7-27 © McGraw-Hill Education. Autotrophs and Their Energy Sources (2 of 3) Chemoautotrophs (lithoautotrophs) survive totally on inorganic substances – Methanogens, a kind of chemoautotroph, produce methane gas under anaerobic conditions (a): © Dr. Adrian Hetzer 7-28 © McGraw-Hill Education. Autotrophs and Their Energy Sources (3 of 3) (b): © Electron Microscope Lab, UC Berkely 7-29 © McGraw-Hill Education.  Heterotrophs and Their Energy Sources (1 of 3) Majority are chemoorganotrophs: – Derive carbon and energy from organic compounds, i.e. aerobic respiration Two categories: – Saprobes: free-living microorganisms that feed on organic detritus from dead organisms  Opportunistic pathogen: if you have a cut the saprobe is opportunistic and will get in and cause an infection.  Facultative parasite: – Parasites: derive nutrients from host  Pathogens  Some are obligate parasites 7-30 © McGraw-Hill Education.  Heterotrophs and Their Energy Sources (2 of 3) The figure of “Heterotrophs and Their Energy Sources.” a) Cell wall acts as a barrier. b) Enzymes are transported outside the wall. 7-31 © McGraw-Hill Education.  Heterotrophs and Their Energy Sources (3 of 3) The figure of “Heterotrophs and Their Energy Sources” continues on this slide. c) Enzymes hydrolyze the bonds on nutrients. b) Smaller molecules are transported across the wall and cell membrane into the cytoplasm. 7-32 © McGraw-Hill Education.  Concept Check: (1) If an organism is degrading large organic molecules to get both carbon and energy, it would be best described as a: A. Photoheterotroph B. Photoautotroph C. Chemoorganotroph D. Chemoautotroph 7-33 © McGraw-Hill Education.  Concept Check: (2) If an organism is degrading large organic molecules to get both carbon and energy, it would be best described as a: A. Photoheterotroph B. Photoautotroph C. Chemoorganotroph D. Chemoautotroph Answer: C 7-34 © McGraw-Hill Education. Transport: Movement of Substances Across the Cell Membrane (1 of 2) Passive transport (no energy required)– does not require energy; substances exist in a gradient and move from areas of higher concentration toward areas of lower concentration. – Diffusion- movement of a molecule from area of greater concentration to less concentration. – Osmosis – diffusion of water (greater water concentration to area of less concentration). – Facilitated diffusion – solutes that require a carrier (moving molecule to a greater concentration to an area of less concentration but it needs the help of a carrier protein to move the molecule. – NEEDS HELP). 7-35 © McGraw-Hill Education. Transport: Movement of Substances Across the Cell Membrane (2 of 2) Active transport – requires energy and carrier proteins; gradient independent – Carrier-mediated active transport – Group translocation – transported molecule chemically altered – Bulk transport – endocytosis, exocytosis, pinocytosis 7-36 © McGraw-Hill Education.  Diffusion and Molecular Motion Net Movement of molecules down their concentration gradient by random thermal movement (passive transport) 7-37 © McGraw-Hill Education. Diffusion of Water: Osmosis (1 of 4) Living membranes generally block the entrance and exit of larger molecules and permit free diffusion of water (passive transport) When concentrations of the solutions differ, one side will experience a net loss of water and the other a net gain of water until equilibrium is reached 7-38 © McGraw-Hill Education. Diffusion of Water: Osmosis (2 of 4) The figure of “Osmosis.” a) Inset shows a close-up of the osmotic process. The gradient goes from the outer container (higher concentration of H2O) to the sac (lower concentration of H2O). Some water will diffuse the opposite direction but the net gradient favors osmosis into the sac. 7-39 © McGraw-Hill Education. Diffusion of Water: Osmosis (3 of 4) The figure of “Osmosis” continues on this slide. b) As the H2O diffuses into the sac, the volume increases and forces the excess solution into the tube, which will rise continually. 7-40 © McGraw-Hill Education. Diffusion of Water: Osmosis (4 of 4) The figure of “Osmosis” continues on this slide. c) Even as the solution becomes diluted, there will still be osmosis into the sac. Equilibrium will not occur because the solutions can never become equal. (Why?) 7-41 © McGraw-Hill Education. Effect of Differing Osmotic Content Solutions (1 of 6) The figure of “Tonicity.” Cells with cell walls Isotonic Solution: Water concentration is equal inside and outside the cell, thus rates of diffusion are equal in both directions. 7-42 © McGraw-Hill Education. Effect of Differing Osmotic Content Solutions (2 of 6) The figure of “Tonicity” continues on this slide. Hypotonic Solution: Net diffusion of water is into the cell; this swells the protoplast and pushes it tightly against the wall. Wall usually prevents cell from bursting. 7-43 © McGraw-Hill Education. Effect of Differing Osmotic Content Solutions (3 of 6) The figure of “Tonicity” continues on this slide. Hypertonic Solution: Water diffuses out of the cell and shrinks the cell membrane away from the cell wall; process is known as plasmolysis. 7-44 © McGraw-Hill Education. Effect of Differing Osmotic Content Solutions (4 of 6) The figure of “Tonicity” continues on this slide. Cells lacking walls Isotonic Solution: Rates of diffusion are equal In both directions. 7-45 © McGraw-Hill Education. Effect of Differing Osmotic Content Solutions (5 of 6) The figure of “Tonicity” continues on this slide. Hypotonic Solution: Diffusion of water into the cell causes it to swell, and may burst it if no mechanism exists to remove the water. 7-46 © McGraw-Hill Education. Effect of Differing Osmotic Content Solutions (6 of 6) The figure of “Tonicity” continues on this slide. Hypertonic Solution: Water diffusing out of the cell causes it to shrink and become distorted. 7-47 © McGraw-Hill Education.  Movement of Solutes: Facilitated Diffusion (1 of 2) Passive transport mechanism that utilizes a carrier protein in the membrane that will bind a specific substance Carrier proteins exhibit specificity (they bind and transport only a single type of molecule) Facilitated diffusion exhibits saturation (rate of transport limited by the number of binding sites on the transport proteins) 7-48 © McGraw-Hill Education. Movement of Solutes: Facilitated Diffusion (2 of 2) 7-49 © McGraw-Hill Education. Carrier Mediated Active Transport (1 of 3) Permeases and pumps: Specific membrane– bound transporter proteins that interact with nearby solute-binding proteins that carry essential solutes (sodium, iron, sugars) Once a solute-binding protein attaches to a specific site in the transporter protein, an ATP is activated and generates energy to pump the solute into the cell’s interior through a special channel. 7-50 © McGraw-Hill Education.  Carrier Mediated Active Transport (2 of 3) The figure of “Carrier Mediated Active Transport.” 7-51 © McGraw-Hill Education.  Carrier Mediated Active Transport (3 of 3) The figure of “Carrier Mediated Active Transport” continues on this slide. a) Carrier-mediated active transport. (1) Membrane-bound transporter proteins (permeases) interact with nearby solute binding proteins that carry essential solutes (sodium, iron, sugars). (2) Once a binding protein attaches to a specific site, an ATP is activated and generates energy to pump the solute into the cell's interior through a special channel in the permease. 7-52 © McGraw-Hill Education.  In Group Translocation (1 of 2) Another type of active transport in which energy is conserved by coupling transport with synthesis A specific molecule is actively captured, but it is chemically altered or activated for use in the cell on its passage through the membrane protein carrier 7-53 © McGraw-Hill Education.  In Group Translocation (2 of 2) b) In group translocation, (1) a specific molecule is actively captured, but on its passage through the membrane protein carrier (2) it is chemically altered or activated for use in the cell. By coupling transport with synthesis, the cell conserves energy. 7-54 © McGraw-Hill Education. Endocytosis: Eating and Drinking by Cells (1 of 2) Endocytosis: bringing substances into the cell through a vesicle or phagosome – Phagocytosis ingests substances or cells (pseudopods) – Pinocytosis ingests fluids and/or dissolved substances (microvilli) 7-55 © McGraw-Hill Education. Endocytosis: Eating and Drinking by Cells (2 of 2) c) Endocytosis. With phagocytosis, solid particles are engulfed by flexible cell extensions or pseudopods (1- 4) (1,000x). (5) With pinocytosis, fluids and/or dissolved substances are enclosed in vesicles by very fine protrusions called microvilli (3.000x). Oil droplets fuse with the membrane and are released directly into the cell. 7-56 © McGraw-Hill Education.  TABLE 7.3 Summary of Transport Processes in Cells (1 of 3) General Nature of Transport Examples Description Qualities Process Energy expenditure by the cell A fundamental Nonspecific is not required. Substances property of Brownian exist in a gradient and atoms and movement Passive Diffusion move from areas of higher molecules that Movement of small osmosis concentration toward areas exist in a state uncharged of lower concentration in of random molecules across the gradient. motion membranes Molecule specific; Molecule binds to a transports both Facilitated carrier protein in ways diffusion membrane and Transports sugars, is carried across amino acids, to other side. water Atoms or molecules Energy expenditure is are pumped into required. Molecules need or out of the cell Carrier- Transports simple not exist in a gradient. by specialized mediated sugars, amino Active Rate of transport is increased. receptors; active acids, inorganic Transport may occur driven by ATP or transport ions (Na+, K+) against a concentration other high- gradient. energy molecules 7-57 © McGraw-Hill Education.  TABLE 7.3 Summary of Transport Processes in Cells (2 of 3) General Nature of Transport Examples Description Qualities Process Molecule is moved across Alternate system membrane and for transporting Group simultaneously nutrients translocation converted to a (sugars, amino metabolically acids) useful substance. Mass transport of Process is large particles, endocytosis; cells, and liquids Bulk transport examples are by engulfment phagocytosis and vesicle and pinocytosis formation 7-58 © McGraw-Hill Education.  TABLE 7.3 Summary of Transport Processes in Cells (3 of 3) General Process: 7-59 © McGraw-Hill Education.  Concept Check: (3) If a cell is in a concentrated glucose solution and the glucose is moving into the cell through a carrier protein, this would be an example of A. Diffusion B. Facilitated Diffusion C. Osmosis D. Endocytosis E. Pinocytosis 7-60 © McGraw-Hill Education.  Concept Check: (4) If a cell is in a concentrated glucose solution and the glucose is moving into the cell through a carrier protein, this would be an example of A. Diffusion B. Facilitated Diffusion C. Osmosis D. Endocytosis E. Pinocytosis Answer: B 7-61 © McGraw-Hill Education. Environmental Factors That Influence Microbes Niche: totality of adaptations organisms make to their habitat Environmental factors affect the function of metabolic enzymes Factors include: – Temperature – Oxygen requirements – pH – Osmotic pressure – Barometric pressure 7-62 © McGraw-Hill Education.  Adaptations to Temperature The range of temperatures for microbial growth can be expressed as three cardinal temperatures (minimum, maximum, and optimum). 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 7-63 © McGraw-Hill Education.  Temperature Adaptation Groups Psychrophiles – optimum temperature below 15°C; capable of growth at 0°C Mesophiles – optimum temperature 20°-40°C; most human pathogens Thermophiles – optimum temperature greater than 45°C 7-64 © McGraw-Hill Education.  Gas Requirements: Oxygen As oxygen is utilized it is transformed into several toxic products: – Singlet oxygen (1O2), superoxide ion (O2-), peroxide (H2O2), and hydroxyl radicals (OH-) Most cells have developed enzymes that neutralize these chemicals: – Superoxide dismutase, catalase If a microbe is not capable of dealing with toxic oxygen, it is forced to live in oxygen free habitats 7-65 © McGraw-Hill Education. Adaptations to Oxygen Requirement (1 of 2) Aerobe – utilizes oxygen and can detoxify it – Obligate aerobe – cannot grow without oxygen – Facultative anaerobe – utilizes oxygen but can also grow in its absence – Microaerophile – requires only a small amount of oxygen 7-66 © McGraw-Hill Education. Adaptations to Oxygen Requirement (2 of 2) Anaerobe – does not utilize oxygen – Obligate anaerobe – lacks the enzymes to detoxify oxygen so cannot survive in an oxygen environment – Aerotolerant anaerobes – do not utilize oxygen but can survive and grow in its presence 7-67 © McGraw-Hill Education. Oxygen Requirement Determination Cultures with reducing media that contain an O2- removing chemical, such as thioglycollate, can help determine the O2 requirements of a microbe The relative position of growth of bacteria that differ in O2 requirements in such culture media provides some indication of their adaptations to O2 use © Terese M. Barta, Ph.D 7-68 © McGraw-Hill Education.  Anaerobic Culture Techniques Growing strictly anaerobic bacteria usually requires special media, methods of incubation, and handling chambers that exclude O2 – Most microbes require some CO2 in their metabolism – Capnophile – grows best at higher CO2 tensions than normally present in the atmosphere 7-69 © McGraw-Hill Education.  Effects of pH Neutrophiles– Majority of microorganisms grow at a pH between 6 and 8 Acidophiles – grow at extreme acid pH Alkalinophiles – grow at extreme alkaline pH 7-70 © McGraw-Hill Education.  Osmotic Pressure Most microbes exist under hypotonic or isotonic conditions Osmophiles – require a high concentration of salt (halophile) – Obligate halophiles grow optimally in solutions of 25% NaCl but require at least 9% NaCl (salt lakes, ponds…)  Halobacterium, Halococcus Osmotolerant – do not require high concentration of solute – Facultative halophiles remarkably resistant to salt  Staphylococcus aureus 7-71 © McGraw-Hill Education.  Other Environmental Factors Pressure – Barophiles – can survive under extreme pressure and will rupture if exposed to normal atmospheric pressure Water – Only dormant, dehydrated cell stages (i.e. spores and cysts) tolerate extreme drying because of the inactivity of their enzymes 7-72 © McGraw-Hill Education.  Concept Check: (5) Chlamydomonas nivalis grows on Alaskan glaciers and it’s photosynthetic pigments give the snow a red crust. This organism would be best described as a A. Psychrophile B. Alkalinophile C. Microaerophile D. Osmotolerant E. Barophile (a and b): Images courtesy of Nozomu Takeuchi 7-73 © McGraw-Hill Education.  Concept Check: (6) Chlamydomonas nivalis grows on Alaskan glaciers and it’s photosynthetic pigments give the snow a red crust. This organism would be best described as a A. Psychrophile B. Alkalinophile C. Microaerophile D. Osmotolerant E. Barophile Answer: A 7-74 © McGraw-Hill Education.  Ecological Associations Among Microorganisms (1 of 2) Microbial Associations: – Symbiotic – Nonsymbiotic Symbiotic: Organisms live in close nutritional relationships; required by one or both members – Mutualism: Obligatory, dependent; both members benefit – Commensalism: The commensal benefits; other member not harmed – Parasitism: Parasite is dependent and benefits; host harmed 7-75 © McGraw-Hill Education.  Ecological Associations Among Microorganisms (2 of 2) Nonsymbiotic: Organisms are free-living; relationships not required for survival – Syntrophy: Members cooperate and share nutrients – Amensalism: Some members are inhibited or destroyed by others 7-76 © McGraw-Hill Education.  Ecological Associations (1 of 21) Symbiosis Two organisms live together in a close partnership Mutualism –both members benefit – Obligate Mutualism require each other to survive  Casseopeia jellyfish and dinoflagellates – Nonobligate Mutualism can be separated and live apart  Ciliophoran Euplotes and unicellular green algae 7-77 © McGraw-Hill Education.  Ecological Associations (2 of 21) Commensalism – commensal benefits, other member neither harmed nor benefited – Haemophilus and Staphylococcus Parasitism – parasite dependent and benefits; host is harmed – Rickettsia and Chlamydia bacteria 7-78 © McGraw-Hill Education.  Ecological Associations (3 of 21) The figure of “Symbiosis.” Obligate Mutualism : Organisms are so intimately associated that they require each other to survive. Root nodules (a1) have nitrogen-fixing endosymbiotic bacteria that supply the plant with usable nitrogen and provide a nurturing habitat for the bacteria (a2 inset). Jellyfish (b1) and corals rely on endosymbiotic algae called dinoflagellates (b2 inset) for survival. 7-79 © McGraw-Hill Education.  Ecological Associations (4 of 21) The figure of “Symbiosis” continues on this slide. (a1): Source: Scott Bauer/USDA; (a2): Louisa Howard - Dartmouth Electron Microscope Facility (a1) Root nodules on a legume; (a2) Bradyhizobium bacteria inside a nodule (3,000x) 7-80 © McGraw-Hill Education.  Ecological Associations (5 of 21) The figure of “Symbiosis” continues on this slide. (b1): © jeridu/Getty Images; (b2): Science History Images/Alamy Stock Photo (b1) A Casseopeia jellyfish gets its color and nutrition from (b2) dinoflagellates (400x). 7-81 © McGraw-Hill Education.  Ecological Associations (6 of 21) The figure of “Symbiosis” continues on this slide. Nonobligate Mutualism: Organisms interact at the cellular level for mutual benefit, but they can be separated and live apart. The protozoan in (c) engulfs the algae but absorbs the nutrients they release and shelters them. (d) The plant supplies nutrients to the fungus and the fungus protects the plants against drying and insects. 7-82 © McGraw-Hill Education.  Ecological Associations (7 of 21) The figure of “Symbiosis” continues on this slide. (c): Courtesy of Dr. Ralf Wagner (c) The ciliophoran Euplotes (800x) harbors unicellular green algae. 7-83 © McGraw-Hill Education.  Ecological Associations (8 of 21) The figure of “Symbiosis” continues on this slide. (d): Source: Nick Hill/USDA (d) Fungal hyphae (blue filaments— 500x) growing in close contact with the cells of a grass leaf. 7-84 © McGraw-Hill Education.  Ecological Associations (9 of 21) The figure of “Symbiosis” continues on this slide. Commensalism: The members have an unequal relationship. One partner is favored by the association and the other is not harmed or helped. (e) Tiny colonies of Haemophilus absorb required growth factors given off by Staphylococcus. (f1 and 2) Human commensals associated with the epidermis make a living off flakes and excretions, generally with neutral effects. 7-85 © McGraw-Hill Education.  Ecological Associations (10 of 21) The figure of “Symbiosis” continues on this slide. (e): © Kathy Park Talaro (e) Satellite Haemophilus colonies clustered around Staphylococcus (white line of growth). 7-86 © McGraw-Hill Education.  Ecological Associations (11 of 21) The figure of “Symbiosis” continues on this slide. (f1): Source: CDC-DPDx /Image courtesy of Dr. CSBR Prasad, Vindhya Clinic and Diagnostic Lab, India; (f2): Source: Janice Carr/CDC. (f1) Demodex mite lives in or around human hair follicles. (100x) and (f2) Micrococcus luteus bacteria live on the skin surface (2,000x) 7-87 © McGraw-Hill Education.  Ecological Associations (12 of 21) The figure of “Symbiosis” continues on this slide. Parasitism: A microbe invades the sterile regions of a host and occupies its tissues and cells, causing some degree of damage. (g) All viruses are parasites that invade cells and take over their function. (h) Malaria shows multilevel parasitism. Mosquitoes (h1) are blood-sucking ectoparasites of humans that carry their own parasites (h2) that can also infect humans. 7-88 © McGraw-Hill Education.  Ecological Associations (13 of 21) The figure of “Symbiosis” continues on this slide. (g): Source: Cynthia Goldsmith/CDC (g) Sin Nombre hantavirus, a human pathogen carried in the waste of mice (5,000x). 7-89 © McGraw-Hill Education.  Ecological Associations (14 of 21) The figure of “Symbiosis” continues on this slide. (h1): Source: James Gathany/CDC; (h2): Source: Blaine A. Mathison/CDC DPDX. (h1) The malaria vector, a female Anopheles mosquito; (h2) malaria parasites (Plasmodium, 1,000x) from blood 7-90 © McGraw-Hill Education.  Ecological Associations (15 of 21) Non-symbiotic When organisms are free-living in a shared habitat Syntrophy (or cross-feeding)– Microbes sharing a habitat feed off substances released by other organism – Azotobacter and Cellulomonas Amensalism – One member of an association produces a substance that harms or kills another (antagonism, competition) – Antibiosis 7-91 © McGraw-Hill Education.  Ecological Associations (16 of 21) The figure of “Non-symbiotic.” Syntrophy: Microbes sharing a habitat feed off substances released by other organisms, (i) Azotobacter releases NH4 that feeds Cellulomonas, and Cellulomonas degrades cellulose that feeds Azotobacter. (j) A dust mite lives in human settings and feeds off dead skin flakes. 7-92 © McGraw-Hill Education.  Ecological Associations (17 of 21) The figure of “Non-symbiotic” continues on this slide. (i) Cycle of cross-feeding in two soil bacteria 7-93 © McGraw-Hill Education.  Ecological Associations (18 of 21) The figure of “Non-symbiotic” continues on this slide. (j): © MedicalRF.com (j) Dermatophagoides mite (100x) 7-94 © McGraw-Hill Education.  Ecological Associations (19 of 21) The figure of “Non-symbiotic” continues on this slide. Amensalism: One member of an association produces a substance that harms or kills another. (k) Ants have complex symbiotic relationships that involve mutualism and amensalism with fungi and bacteria. (l1 and l2) In the amensal phase of their ecology, the ants cultivate actinomycetes to protect their habitat from microbial pests. 7-95 © McGraw-Hill Education.  Ecological Associations (20 of 21) The figure of “Non-symbiotic” continues on this slide. (k): © Paul Bertner/Getty Images RF (k) Leaf cutting ants gathering food for a fungus garden that is their source of food. 7-96 © McGraw-Hill Education.  Ecological Associations (21 of 21) The figure of “Non-symbiotic” continues on this slide. (l1): Source: Jörg Barke, Ryan F Seipke, Sabina Grüschow, Darren Heavens, Nizar Drou, Mervyn J Bibb, Rebecca JM Goss, Douglas W Yu, and Matthew I Hutchings; (l2): © Microfield Scientific Ltd/Science Source (l1) Antibodies by an actinomycete against a pathogenic fungus;(l2) micrograph of actinomycete (800x) 7-97 © McGraw-Hill Education.  Other Microbial Relationships: 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 – Communicate and cooperate in the formation and function of biofilms – quorum sensing 7-98 © McGraw-Hill Education.  Biofilm Formation and Quorum Sensing (1 of 2) The figure of “Biofilm Formation.” 7-99 © McGraw-Hill Education.  Biofilm Formation and Quorum Sensing (2 of 2) The figure of “Biofilm Formation” continues on this slide. 1. Free-swimming cells lose their motility and settle down onto a surface or substrate. 2. Cells synthesize an adhesive matrix that holds them tightly to the substrate. 3. When biofilm grows to a certain density (quorum), the cells release inducer molecules that can coordinate a response. 4. Enlargement of one cell to show genetic induction. Inducer molecule stimulates expression of a particular gene and synthesis of a protein product, such as an enzyme. 5. Cells secrete their enzymes in unison to digest food particles. 7-100 © McGraw-Hill Education. Interrelationships Between Microbes and Humans Human body is a rich habitat for symbiotic bacteria, fungi, and a few protozoa - normal microbial flora Commensal, parasitic, and synergistic relationships 7-101 © McGraw-Hill Education.  The Study of Microbial Growth Microbial growth occurs at two levels: growth at a cellular level with increase in size, and increase in population Division of bacterial cells occurs mainly through binary fission (transverse) – Parent cell enlarges, duplicates its chromosome, and forms a central transverse septum dividing the cell into two daughter cells 7-102 © McGraw-Hill Education.  Binary Fission (1 of 3) The figure of “Binary Fission.” 1. A parent cell at the beginning of the cell cycle: What cannot be seen is the synthesis and activity gearing up for cell division. 2. Chromosome replication and cell enlargement: The parent cell duplicates the chromosome and synthesizes new structures that enlarge the cell in preparation for the daughter cells. 3. Chromosome division and septation: The chromosomes affix to the cytoskeleton and are separated into the forming cells. The cell lays down a septum that begins to wall off the new cells. Other components (ribosomes) are equally distributed to the developing cells. 7-103 © McGraw-Hill Education.  Binary Fission (2 of 3) The figure of “Binary Fission” continues on this slide. 4. Completion of cell compartments: The septum is synthesized completely through the center, and the cell membrane patches itself so that there are two separate cell chambers. 5. End of cell division cycle: Daughter cells are now independent units. Some species will separate completely as shown here, while others will remain attached, forming chains or pairs, for example. 7-104 © McGraw-Hill Education.  Binary Fission (3 of 3) The figure of “Binary Fission” continues on this slide. 7-105 © McGraw-Hill Education. Rate of Population Growth (1 of 4) Time required for a complete fission cycle is called the generation, or doubling time Each new fission cycle increases the population by a factor of 2 – exponential growth Generation times vary from minutes to days 7-106 © McGraw-Hill Education. Rate of Population Growth (2 of 4) 7-107 © McGraw-Hill Education.  Rate of Population Growth (3 of 4) *Note that the left scale is logarithmic and the right scale is arithmetic 7-108 © McGraw-Hill Education. Rate of Population Growth (4 of 4) Equation for calculating population size over time: Nf  Ni 2n Nƒ is total number of cells in the population Ni is starting number of cells Exponent n denotes generation time 2n number of cells in that generation 7-109 © McGraw-Hill Education.  Concept Check: (7) Escherichia coli has a doubling time of 20 minutes. If there are 5 cells at the beginning of the experiment, how many will there be in 3 hours? A. 215 B. 6,000 C. 712 D. 2560 7-110 © McGraw-Hill Education.  Concept Check: (8) Escherichia coli has a doubling time of 20 minutes. If there are 5 cells at the beginning of the experiment, how many will there be in 3 hours? A. 215 B. 6,000 C. 712 D. 2560 Answer: D 7-111 © McGraw-Hill Education. Determinants of Growth: Viable Plate Count * The culture is probably in lag period with no few cells added. 7-112 © McGraw-Hill Education.  Stages in the Population Growth Curve (1 of 2) In laboratory studies, populations typically display a predictable pattern over time – growth curve Stages in the normal growth curve: 1. Lag phase – “flat” period of adjustment, enlargement; little growth 2. Exponential growth phase – a period of maximum growth when cells have adequate nutrients and a favorable environment 3. Stationary phase – rate of cell growth equals rate of cell death caused by depleted nutrients and O2, excretion of organic acids and pollutants 4. Death phase – as limiting factors intensify, cells die exponentially 7-113 © McGraw-Hill Education. Stages in the Population Growth Curve (2 of 2) 7-114 © McGraw-Hill Education.  Methods of Analyzing Population Growth (1 of 5) Turbidometry – most simple – Degree of cloudiness, turbidity, of the nutrient culture media reflects the relative population size © K. Talaro 7-115 © McGraw-Hill Education.  Methods of Analyzing Population Growth (2 of 5) Enumeration of bacteria: – Viable colony count – Direct cell count – (manually or automated) counting the number of cells in a sample microscopically 7-116 © McGraw-Hill Education.  Methods of Analyzing Population Growth (3 of 5) Counting cells in direct count can be automated by sensitive devices: – Coulter counter – Flow cytometer 7-117 © McGraw-Hill Education. Methods of Analyzing Population Growth (4 of 5) 7-118 © McGraw-Hill Education. Methods of Analyzing Population Growth (5 of 5) 7-119 © McGraw-Hill Education.  End of Presentation 3-120 © McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom. No reproduction or further distribution permitted 7-120 without the prior written consent of McGraw-Hill Education.