Micro303Lecture12 - Microbiology 303 Fall 2012 Lecture 12 Microbial Nutri6on and growth Outline Determinants of growth Nutrients Environmental condi6ons

Micro303Lecture12 - Microbiology 303 Fall 2012 Lecture 12...

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Unformatted text preview: Microbiology 303 Fall 2012 Lecture 12 Microbial Nutri6on and growth Outline •  Determinants of growth –  Nutrients –  Environmental condi6ons •  Defining and monitoring growth –  Media: growth in the lab –  Defining growth –  Phases of growth –  Quan6fying growth •  Limits to growth and microbial adapta6ons •  Control of growth Building the cell Energy light chemicals Carbon CO2 CH4 Organic chemicals Other nutrients Nitrogen Phosphorus etc Brock fig 1.2 b Appropriate environmental condi6ons Energy •  Source of energy to fuel cell func6ons –  Chemical energy = chemotroph •  Organotroph = uses organic donors •  Lithotroph = uses inorganic donors –  Light energy = phototroph •  Mechanism to store and transfer energy –  ATP and other chemicals  ­ in cytoplasm –  Ion mo6ve force – across membrane Macronutrients: assimila6on •  Carbon •  Nitrogen •  Phosphorus –  Usually assimilated as phosphate (PO43 ­) •  Sulfur –  Usually assimilated as sulfides (H2S, S2 ­, HS ­) or organic sulfur (e.g. cysteine and methionine) –  Some microbes can reduce sulfate (SO42 ­) to sulfide •  Hydrogen and Oxygen Carbon assimila6on about 50% of cell dry weight Methane oxida6on CH4 Carbon dioxide reduc6on “fixa6on” Organic C (CH2O) CO2 Autotrophs Methanotrophs Heterotrophs Cell C (CH2O) Autotrophic microbes Take CO2 and convert it to cellular material requires energy input (ATP) and reducing power (NADPH) PHOTOAUTOTROPHS Cyanobacteria CHEMOLITHOAUTOTROPHS Nitrifiers Green non ­sulfur bacteria Green sulfur bacteria Hydrogen Oxidizers Sulfur Oxidizers Heterotrophic microbes Take organic material and convert it to cellular material PHOTOHETEROTROPHS Heliobacteria CHEMOHETEROTROPHS Halophilic archaea So many….. Chlamydia Some purple bacteria Enterics Lactococcus and streptococcus Nitrogen assimila6on about 15% dry weight of cell Assimila6ve Nitrate reduc6on NH3 N2 Nitrogen fixa6on Organic N Cell N NO3 ­ Micronutrients cell has separate transport mechanisms for all these •  Magnesium: stabilizes ribosome, needed for ATP ­dependent reac6ons •  Potassium: main cellular ca6on •  Calcium: not essen6al for all cells •  Sodium: not essen6al for all cells •  Iron: needed for many enzymes Iron acquisi6on Siderophores = small molecules that bind iron Microbial Iron needs and Us •  Humans control iron accessibility in the body using iron ­binding proteins (nutri6onal immunity) •  Intracellular iron is bound by ferri6n (Fn) or present as heme (in hemoglobin, Hb) •  Extracellular iron is bound by transferrin (Tf) or lactoferrin (Lf) •  Combined with aerobic environment and neutral pH, free iron is very rare in vertebrate 6ssues and fluids Iron acquisi6on for host ­associated microbes Produce siderophores Hemophores are proteins that extract heme from hemoproteins Produce hemophores Bind proteins Skaar 2010 PLoS Pathogens 6(8): e1000949 Trace elements cell has separate transport mechanisms for all these •  •  •  •  •  •  •  •  •  •  •  Boron Chromium Cobalt Copper Manganese Molybdenum Nickel Selenium Tungsten Vanadium Zinc Used in many coenzymes and as cofactors for enzymes Use is variable in microbes Growth Factors •  Organic compounds needed by some cells, because they can’t make their own Nutri6onal independence •  Nutri6onally independent –  Obtain simple chemicals from environment –  Use these to make all cell needs –  Have many catabolic and anabolic pathways •  Nutri6onally dependent  ­ fas5dious –  Ojen lack anabolic and catabolic pathways –  Need nutrients and growth factors supplied to them Environmental parameters determine growth All organisms need appropriate environmental condi6ons for growth Temperature pH Oxygen Water availability For microbes, internal temperature = outside temperature Individual spp. have a defined growth range of 30 to 40 ˚C Effects of temperature on growth •  Low: membrane fluidity decreases, rate of enzyma6c reac6ons slows down •  High: membrane fluidity increases too much, thermal denatura6on of protein •  Within range, microbes adapt by changing membrane lipids and producing isozymes of enzymes Temperature extremophiles •  Thermophiles –  Habitats include hot springs, ar6ficial thermal sources, hydrothermal vents, compost piles –  Adapta6ons include heat ­stable proteins and saturated fany acids in lipids and ether linked lipids –  Includes Bacteria and Archaea; Eukarya are more limited •  Psychrophiles –  Habitats include Arc6c and Antarc6c regions, glaciers, high al6tudes, oceans, caves, refrigerators, atmosphere –  Adapta6ons include cold ­stable enzymes, unsaturated and polyunsaturated fany acids in lipids –  Includes Bacteria, Archaea, and Eukarya Psychrotolerant microbes: psychrotrophs •  Mesophiles that can grow at cold temperatures •  Example: Listeria monocytogenes –  Firmicute –  Found widely in soil and water and on plants –  Grows even in the refrigerator –  Causes food poisoning Environmental parameters for growth: pH pH extremophiles •  Acidophiles –  Habitats include acid mine drainage, acid hot springs, volcanic soils, acidic soils, geothermal vents –  Also mammalian GI tract –  Bacteria and Archaea and also Fungi •  Alkalophiles –  Habitats include soda lakes, alkaline soils –  Also insect GI tract –  Bacteria and Archaea Environmental parameters for growth: Water availability (Free) Water availability Decrease water amount Xerophiles Increase solute concentra6on Halophiles Growth in high salt: some halophiles require increased salt Maintaining osmo6c balance Hypotonic solu6on Hypertonic solu6on e.g. glycerol, sucrose, etc Cells accumulate compa6ble solutes to combat osmo6c stress Environmental parameters for growth: Oxygen Growth in the presence of oxygen does not mean the organism is using oxygen Obligate anaerobes are abundant in nature but require special techniques for growth in the lab •  •  •  •  •  Soils Sediments Landfills Aqua6c habitats Animal GI tracts and on surfaces •  Also some anaerobic fungi and pro6sts Glove box Reac6ve oxygen species Detoxifying enzymes Bioprospec6ng: Applica6ons of extremophiles Enzymes and molecules from thermophiles, psychrophiles, acidophiles, alkalophiles, etc, are useful in industrial applica6ons The human landscape: extreme? Anaerobes Xerophiles Halophiles Acidophiles Acidophiles Anaerobes Helicobacter pylori Lives in the human stomach Causes ulcers (Marshall) linked to stomach cancer About 50% of people normally have H. pylori in stomach •  Colonizes gastric mucosa •  Produces urease, which degrades urea to CO2 and NH3 •  •  •  •  Staphylococcus epidermidis Has mul6ple sodium ion transporters and mul6ple osmoprotectant transporters Microbial growth in the lab: culturing Growth of microbes requires that we know their nutri6onal and environmental needs Thousands of different media developed to grow microbes S6ll, we probably can’t yet grow most microbes in the lab Types of media Defined •  Insert table of brock 5.4 Complex Other types of media •  Differen5al –  Allows us to iden6fy microbes by a reac6on in the medium •  Selec5ve –  Favor the growth of some microbes and disfavor others –  Every medium is selec5ve Growth in the lab versus growth in the environment •  Presence of other microbes –  Syntrophy •  Unpredictable nutrient supplies –  Copiotrophs – adapted to high levels –  Oligotrophs – adapted to low levels •  Unique microenvironments –  Capnophiles – need increased CO2 levels •  Growth on surfaces (biofilms) versus growth suspended in liquid (planktonic) ...
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