microbial nutrition and growth - weber state university slides/microbial nutrition...microbiology:...
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Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 1
Microbial Nutrition
n All life requires: ¨ Electron flow, to drive all life processes
n Drives ions into, out of cells n Used to create ATP
¨ Energy, to move electrons
¨ Materials, to make cell parts n Nutrients
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 2
Microbial Nutrition
n Electron flow requires:
¨ Source of electrons n Lithotrophs
¨ Inorganic molecules are electron donors
n Organotrophs ¨ Organic molecules are electron donors
¨ Ultimate electron acceptor n Inorganic molecules
¨ Respiration
n Organic molecules ¨ Fermentation
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 3
Microbial Nutrition
n Source of energy
¨ Phototrophs n Light energy excites electrons n Excited molecules are electron donors
¨ Chemotrophs n Chemicals are electron donors n Oxidation of chemical
¨ Oxidation = donation of electrons ¨ Electron acceptor is reduced
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 4
Microbial Nutrition
n Nutrients
¨ Must be supplied from environment ¨ Macronutrients
n Major elements in cell macromolecules ¨ C, O, H, N, P, S
n Ions necessary for protein function n Mg2+, Ca2+, Fe2+, K+
¨ Micronutrients n Trace elements necessary for enzyme function
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 5
Microbial Nutrition
n Different microbes require different
additional nutrients ¨ Amino acids ¨ N from air (N2) vs. from soil, other organisms ¨ Electron acceptors
n Aerobic (O2) vs. anaerobic organisms
¨ Energy source n Light vs. organic energy source
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 6
Nutrient Uptake
n Passive diffusion ¨ Some gases pass freely through membranes
n O2, CO2
¨ Follows gradient of material n Facilitated diffusion
¨ Transporters pass material into/out of cell
¨ Follows gradient of material
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 7
Nutrient Uptake—Active Transport
n ABC Transporters ¨ Use ATP energy to pass
material into cell ¨ Transport material against
gradient
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 8
Nutrient Uptake—Active Transport
n Symport and Antiport ¨ Gradient of one molecule transports another
n Electron transport creates Proton-Motive Force n PMF transports other molecules
¨ Transports material against its gradient Symport: Gradient of pumps in same direction
Antiport: Gradient of pumps in opposite direction
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 9
Nutrient Uptake—Active Transport
n Phosphotransferase System (PTS)
¨ Uses ATP energy to pass material into cell
¨ Modifies material as it enters cell n Gradient is maintained,
pushing material into cell
glucose enters cell and is phosphorylated. As a result, gradient of pushes more glucose inside. (glucose-6-phosphate) cannot pass out of cell.
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 10
Animation: Phosphotransferase System (PTS) Transport
Nutrient Uptake—Active Transport
Click box to launch animation
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 11
Culturing Bacteria
n Culture media has all materials necessary for growth ¨ Varies for different bacterial species ¨ Electron source ¨ Energy source
n If not phototrophic
¨ Carbon source n If not autotrophic
¨ Nitrogen source n If not N2-fixer
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 12
Obtaining Pure Cultures
n Dilution streaking
¨ Streak cells on plate ¨ Agar inhibits spread of
microbes on plate ¨ All cells in colony derive
from single cell n Genetically identical n Clone of that original cell
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 13
Obtaining Pure Cultures
n Dilution in liquid culture
¨ Reduces number of cells in each tube ¨ Spread liquid on plate to see single colonies
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 14
Counting Bacteria
n Petroff-Hauser chamber ¨ Counts cells directly ¨ Gives accurate number ¨ Can’t tell if cells are alive or dead
n Use stain to distinguish living cells
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 15
Counting Bacteria
n Spectrophotometer
¨ Measures optical density n “Shadow” of bacteria
¨ Gives rapid measurement ¨ Can’t tell if cells are alive or dead ¨ Solution must be at 107–1010 cells/ml
Drawing of light bulb Photodetector
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 16
Counting Bacteria
n Viable counts
¨ Counts only cells able to reproduce n Form colonies
¨ Requires time to form colonies (overnight)
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 17
The Growth Cycle
n Lag phase
¨ Cells synthesizing materials, not dividing n Log phase = exponential growth
¨ 1 → 2 → 4 → 8 → 16 … n 10 doublings increases density by ~1000 n log10(N) increases linearly
n Stationary phase ¨ Cells no longer growing
n Death phase
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 18
The Growth Cycle
Log scale necessary to show wide range of concentrations
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 19
Cell Differentiation
n Cells respond to changing environment
¨ Endospores n Protect against bad conditions n Disseminates cells
¨ Forms inside (“endo”) mother cell
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 20
Cell Differentiation
n Cells respond to changing environment
¨ Heterocysts n Different cells produce different
nutrients ¨ Vegetative cells—energy ¨ Heterocysts—fixed nitrogen
¨ Myxospores n Form inside fruiting body
¨ Multicellular structure
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 21
Cell Differentiation
n Cells respond to changing environment
¨ Actinomycetes form spores n Food runs out n Produce aerial hyphae n Protect against bad conditions n Disseminates cells
Spores
Microbiology: An Evolving Science © 2009 W. W. Norton & Company, Inc. 22
Biofilms
n Cells secrete material to hold to a surface ¨ Cells acting together
n Multiple species or a single species
¨ Cells signal to each other n Quorum sensing
¨ Protects against dispersion ¨ Prevents antibiotics
from infiltrating