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118 Cards in this Set

  • Front
  • Back
The Importance of Microorganisms (just a few examples)
• Provide nitrogen for plants
• Help cows and sheep digest cellulose
• Degrade wastes
• Make wine and cheese
• Develop vaccines and antibiotics
• Cause pathogenic disease
Antoni van Leeuwenhoek (1632-1723)
o Developed the first simple microscope (much like a magnifying glass)
o Allowed him to examine, for the first time, the microbial world
o Examined tiny animals, fungi, algae, protozoa - animalcules
o Reported the existence of protozoa in 1674
o Reported the existence of bacteria in 1676
Carolus Linnaeus (1707-1778)
o Developed a taxonomic system for naming and grouping plants and animals
Eukaryotes – complex organisms with a true nucleus and membrane-bound organelles
 Kingdom Plantae
 Kingdom Animalia
 Kingdom Fungi
 Kingdom Protista
Prokaryotes – simple organisms that lack a true nucleus and lack membrane-bound organelles
 Kingdom Bacteria
 Kingdom Archaea
Fungi
 Kingdom Fungi
 Eukaryotic
 Have cell walls
 Obtain food from other organisms
 Examples include molds and yeasts
Protozoa
 Kingdom Protista
 Eukaryotic
 Simplest eukaryotic organisms
 Single-celled
 Examples include Amoeba and Euglena
Algae
 Kingdom Protista
 Eukaryotic
 Plant-like
 Photosynthetic
 Examples include kelp and diatoms
Bacteria
 Kingdom Bacteria
 Prokaryotic
 Streptococcus, Staphylococcus
Archaea
 Kingdom Archaea
 Prokaryotic
 Extremophiles
Parasites
 Kingdom Animalia
 Eukaryotic
Viruses
 Not considered “alive”
• Acellular
• Obligatory intracellular parasites
• Do not replicate themselves (rely on host cell machinery)
• Do not carry out typical cellular functions
 Remained undiscovered until the development of the electron microscope (1932)
Theory of spontaneous generation
 Living organisms can arise from non-living matter
 Proposed by Aristotle (384-322 BC)
 Widely accepted for 2000 years
 Francesco Redi (1626-1697) challenged this theory
• See Redi’s meat experiment
 Louis Pasteur (1822-1895) disproved theory
• See Pasteur’s swan-necked flask experiments
 Spontaneous generation debate led the way to the development of the scientific method
Fermentation
o Pasteur’s investigations led to the discovery that yeast was responsible for producing alcohol
Disease
o Prior to 1800, disease was attributed to evil spirits, sin, body fluid imbalance, foul vapors
o Germ Theory of Disease
 Diseases are caused by microorganisms
Nosocomial infections
(infections acquired in a healthcare facility) were rampant in the mid-19th century
Ignaz Semmelweis (1818-1865)
 Noticed lower infection rate when women giving birth were attended by midwives (as opposed to medical students)
 Required medical students to wash their hands, reducing the rate of infection
Joseph Lister (1827-1912)
 Used phenol to reduce the spread of disease
 Founder of antiseptic surgery
Edward Jenner (1749-1823)
 Created the first vaccine (from Vaccinia virus)
 Noticed that cowpox provided protection against smallpox
Robert Koch (1843-1910) (Kochs’s postulates)
 A set of steps taken to prove the cause of infectious disease
 Koch’s Postulates
• The suspected causative agent must be found in every case of the disease and be absent from healthy hosts
• The agent must be isolated and grown outside the host
• When the agent is introduced to a healthy, susceptible host, the host must get the disease
• The same agent must be re-isolated from the diseased experimental host
Number of Elements in Universe vs. Biology
o 93 naturally occurring elements
o 20 elements utilized by living organisms
Synthesis reactions
 Form larger more complex molecules via dehydration synthesis
• Two small molecules joined by a covalent bond
• A water molecule is lost
• Sometimes called condensation reactions
• Anabolism – sum of synthesis reactions in an organism
Decomposition reactions
 Large molecules are broken down via hydrolysis
• Opposite of dehydration synthesis reaction
• A water molecule (facilitated by an enzyme) is used to break the covalent bonds of large molecules
• Catabolism – sum of decomposition reactions in an organism
Exchange reactions
 Atoms are exchanged between reactants
 Example: the phosphorylation of glucose
Lipids
 Four major groups of lipids: fats, phospholipids, waxes, and steroids
Carbohydrates
 Serve as structural framework (chitin and cellulose) and provide building materials for cells.
 Contain carbon, hydrogen, and oxygen in the ration 1:2:1 (Glucose C6H12O6)
Disaccharaides
o Two monosaccharides covalently bonded (by dehydration synthesis).
o Sucrose (table sugar) is glucose + fructose.
o Lactose (milk sugar) is glucose + galactose.
o Maltose (grain sugar) glucose + glucose
Polysaccharides
o Many covalently linked monosaccharides.
o Energy storage
 Starch – energy storage in plants. Starches are long chains of glucose
 Glycogen – energy storage in animals
o Structural
 Cellulose
All living things share four processes
o Growth – an increase in size
o Reproduction – an increase in number
o Responsiveness – an ability to react to environmental stimuli
o Metabolism – controlled chemical reactions
Viruses are not “alive” because
o Cannot grow
o Cannot reproduce without host cell machinery
Glycocalyx (Prokaryotes)
o Gelatinous, sticky substance surrounding the outside of the cell
o Called a capsule if firmly attached to cell surface
 Protect cells from phagocytosis
o Called a slime layer if loose and water-soluble
 Enable cells to adhere to substrates
o Both capsules and slime layers
 Prevent dessication
 Help with pathogenecity
Flagella (Prokaryotes)
 Peritrichous flagella – cover the cell
 Polar flagella – found at rear
Fimbriae (Prokaryotes)
 Short, sticky, proteinaceous, nonmotile extensions present in some bacteria
 Helps cells “stick together” and to their substrates
Pili (Prokaryotes)
 Hollow, nonmotile tubes of protein
 Connect and join cells for conjugation (movement of DNA from one cell to another)
Peptidoglycan
 A complex polysaccharide found in most bacterial cell walls
Gram- positive
 Indicates that a bacterium has a thick layer of peptidoglycan
 Retain the dye crystal violet (during Gram Stain procedure)
• Cell looks purple
Gram-negative
 Indicates that a bacterium has a thin layer of peptidoglycan surrounded by a lipopolysaccharide (LPS) layer
 During infection, Lipid A (from the LPS layer), from the deteriorating Gram negative bacteria enter the blood causing fever, etc.
 Does not retain the crystal violet during Gram stain, but takes up the counterstain, safranin
• Cell looks pink or red
Archael Cell Walls
o Lack peptidoglycan
o Do, however stain with Gram stain
 Gram positive have thick walls, retain the purple dye, crystal violet
 Gram negative have a layer of protein that stain with the red/pink dye, safranin
Prokaryotic Cytoplasmic Membranes
• All bacteria have a membrane that may or may not be surrounded by a glycocalyx and/or cell wall
• Cell membranes of bacteria are composed of a phospholipid bilayer
• Archaea do not have a phospholipid bilayer
Function of the prokaryotic cell membrane
o Separates the internal components from the “outside” world
o Selectively permeable
o Embedded proteins facilitate the passage of substances into and out of the cell
Passive processes – require no energy
o Simple diffusion – movement of substances down a concentration gradient
o Facilitated diffusion – movement of substance, through proteins, down a concentration gradient
o Osmosis – diffusion of water
Active processes – require energy
o Energy required in the form of ATP
o Substances are moved up a gradient
o Active transport – process that uses ATP energy to move needed substance uphill (against a concentration gradient)
Hypertonic solution
 higher concentration of solutes (than on the inside of the cell)
• Water always moves toward the hypertonic solution
Hypotonic solution
 lower concentration of solutes (than on the inside of the cell)
Isotonic solution
 equal concentration of solutes on either side of the cell
• No net movement of water
Cytosol (Prokaryotes)
o Liquid portion of cytoplasm
 Contains water, ions, carbohydrates, proteins, inclusions, endospores, nonmembranous organelles
 Contains DNA
Inclusions (Prokaryotes)
o Lipid, starch (or other) reserves (for energy)
o Gases also stored
Endospores (Prokaryotes)
a dormant, tough, and non-reproductive structure produced by Gram-positive bacteria from the Firmicute phylum which forms when a bacterium produces a thick internal wall that encloses its DNA and part of its cytoplasm
o produced under stress (lack of nutrients, etc.)
o can survive harsh conditions
Nonmembranous Organelles (Prokaryotes)
o Ribosomes (70S)
 Site for protein synthesis
o Cytoskeleton
 Internal network of protein fibers that give shape to the cell
Glycocalyces (Eukaryotes)
o Gelatinous, sticky substance surrounding the outside of the cell
o Absent in eukaryotes that have cell walls
o Animals and protozoans have glycocalysed anchored in cell membrane
o Functions:
 Provide strength
 Provide protection from dehydration
 Cell-to-cell recognition
Flagella (Eukaryotes)
o Long, whip-like extensions (composed of microtubules)
o For movement
Cilia
o Short, numerous extensions
o Extension beat rhythmically to propel cells (or substances)
Eukaryotic Cell Walls
• Cells walls of fungi, algae, plants, protozoa
o Composed of polysaccharides (different from bacteria)
 Plants have cell wall of cellulose
 Fungi have cell wall of chitin (+)
 Algae have cell wall of agar, carrageenan, algin, or other
o Provides protection
o Provide shape and support
Eukaryotic Cell Membranes
• ALL eukaryotic cells have a cell membrane!
o Composed of a phospholipid bilayer
o Protects internal portion of cells from the “outside”
o Acts as a gatekeeper allowing some substance to pass
Nonmembranous Organelles (Eukaryotes)
o Ribosomes (80s)
 Site for protein synthesis
o Cytoskeleton
 Composed of proteins that provide structural support
 Anchor organelles
 Cell movement
o Centrioles
 Animals and fungi
 Composed of microtubules
 Play a role in mitosis
Smooth Endoplasmic Reticulum
Membranous Organelle
• Lipid and carbohydrate synthesis
• Transport
Rough Endoplasmic Reticulum
Membranous Organelle
• Protein production
• “rough” contributed by presence of ribosomes
Lysosomes, peroxisomes, vacuoles, vesicles
Membranous Organelles
 Vesicles and vacuoles
• Membranous “sacs”
• Storage
 Lysosomes
• Vesicle containing hydrolytic enzymes (digestive)
• Peroxisomes
o Some contain catalase for breakdown of hydrogen peroxide
Mitochondrion
Membranous Organelle
 Powerhouse of the cell
 Site for aerobic cellular respiration
Chloroplast
Membranous Organelle
 Plants, algae
 Site for photosynthesis
Metric system (meters)
kilometer (10^3), meter, decimeter (10^-1), centimeter (10^-2), millimeter (10^-3), micrometer (10^-6), nanometer (10^-9)
Visible Light Spectrum
400 to 750 nm
Resolving Power of Most Light Microscopes
0.2 μm
Bright-field Light Microscopy
 Most common
 Background is illuminated
 Light travels through specimen and enters the objective
Dark-field Light Microscopy
 Used to view pale objects
 Light passes through specimen at an oblique angle
 Only light deflected by the specimen enters the objective
 Specimen appears against dark background
Fluorescent Light Microscopy
 UV light passes through specimen that is stained with a fluorescent dye
Transmission Electron Microscope (TEM)
 Beam of electrons passes through specimen
 Magnetic field gathers the electron beams
 Fluorescent screen changes electron image to visible light image
Scanning Electron Microscope (SEM)
 Specimen coated with metal (platinum or gold)
 Beam of electrons passes over specimen surface
 Coated specimen deflects electrons
 Detector and photomultiplier display image on a monitor
chromophores
dyes used for staining to increase contrast (differences in intensity between two objects or between an object and its background)
Preparing Specimens for Staining
o Prepare smear
o Fix slide
 Heat fixation or chemical fixation
o Add dye
Staining
• Simple stains
o Use a single dye (i.e. crystal violet)
• Differential stains
o Use more than one dye to distinguish more than one structure (i.e Gram Stain)
Procedure for Gram Stain (distinguishes between gram positive and gram negative cell walls)
 Flood the smear with the primary stain, crystal violet, and rinse
 Flood the smear with the mordant, iodine, and rinse
 Flood the smear with the decolorizing agent, a solution of ethanol and acetone, and rinse
 Flood the smear with the counterstain, safranin, and rinse
Acid-fast stain – identifies cells with a waxy cell wall (i.e. Mycobacterium)
 Ziehl-Neelsen acid fast staining procedure (direct from Bauman, pg 109)
• Prepare smear
• Cover smear with tissue paper for retaining dye
• Flood smear with carbolfuchsin (red) for several minutes, while warming it over steaming water
o The steam helps the stain get into the waxy cell wall
• Remove tissue paper, coo slide, decolorize with HCL and alcohol
o Only cells without waxy wall will decolorize
o Cells with waxy wall will retain stain
• Counterstain, methylene blue (blue) will stain cells without waxy cell wall
Schaffer-Fulton endospore stain – heat is used to drive malachite green into the normally impermeable endospore
 used for Bacillus and Clostridium
Biological Taxa
o Domain (proposed by Carl Woese)
 Domains are categories based on three different types of rRNA sequences
• Eukarya
• Bacteria
• Archaea
o Kingdom
o Phylum
o Class
o Order
o Family
o Genus
o Species
Taxonomic and Identifying Characteristics
• Five procedures help taxonomist identify and classify microorganisms
o Physical characteristics
o Biochemical tests
 Microbes differ in their ability to utilize and/or produce certain chemicals
o Serological tests
 Antigen-antibody relationship reveals agglutination if particular organisms are present
o Phage typing
 Bacteriophages are used to identify susceptible microorganisms
o Nucleic acid sequencing
Taxonomic Keys
• Dichotomous keys provide stepwise choices between paired characteristics to assist in identifying microorganims
Naming of Enzymes
o Named according to their activity or “job category”
 Hydrolases – promote hydrolysis
 Phosphatases – catalyze the removal of a phosphate
 Synthases and synthetases facilitate dehydration synthesis or condensation reactions
 Dehydrogenases – remove hydrogen atoms from their substrates
o Name indicates substrate of the enzyme and job category
 Lactic acid dehydrogenase – removes hydrogen atoms from lactic acid
Temperature and enzyme activity
 Rate of reaction may proceed faster with increases in temperature (because molecules are colliding faster).
 Optimum temperature – temperature at which an enzyme functions at its best.
 Too much of an increase in temperature, will denature the enzyme, it will no longer be functional.
pH and enzyme activity
 Optimum pH – pH at which an enzyme functions at its best.
 Differences in pH can disrupt the bonding patterns exhibited by the amino acids in a protein, changing the shape of a protein.
Salt and enzyme activity
 Salts dissociate into ions that destroy normal bonding patterns in an enzyme. Curing meat involves using salt, the salt destroys bacterial enzymes, prevents microbial growth.
Enzyme concentration and enzyme activity
 Increasing enzyme concentration will increase the rate of the reaction, but saturation can occur.
Inhibitors and enzyme activity
substance that binds to an enzyme and deactivates it or decreases activity
 Competitive inhibitor – compete for the active site of an enzyme, displacing some of the substrate molecules.
• poisons can act as competitive inhibitors by blocking active sites of enzymes needed for important metabolic reactions
 Noncompetitive inhibitors – bind to the enzyme (at the allosteric site or on/off switch) causing a conformational change in the enzyme; the active site is blocked.
• Allosteric inhibitor – inhibitors that bind to the allosteric site; decreasing enzyme activity
Activators and enzyme activity
bind to allosteric sites, keeping enzymes in their active configurations, increasing enzyme
Enzyme Helpers and enzyme activity
o Cofactors – inorganic molecules required by enzymes to function properly (metal ions like zinc, molybdenum, manganese). Or, organic molecules called coenzymes
o Coenzyme – non-protein organic molecule that acts as an enzyme helper (energy carrier) by acting as an electron donor or acceptor. Many vitamins (water-soluble B vitamins) are coenzymes.
 Important coenzymes in cellular respiration
• NAD+ - nicotinamide adenine dinucleotide, reduced to NADH
o NAD+ acts as an electron and hydrogen acceptor; reduced to NADH.
• FAD – flavin adenine dinucleotide; reduced to FADH2
 Important coenzyme in photosynthesis
• NADP+ - Nicotinamide adenine dinucleotide phosphate, reduced to NADPH
End products of glycolysis
o Four ATP are made during glycolysis (substrate level phosphorylation), but 2 ATP used to get reaction started
 Substrate level phosphorylation – generation of ATP by direct transfer of phosphate to ADP from another phosphorylated molecule
o Glucose intermediates are oxidized and 2 NAD+ are reduced to 2 NADH
o Glucose is converted to two 3-carbon molecules of pyruvate (pyruvic acid)
Alternatives to Glycolysis
(only produce one molecule of ATP per glucose)
o Pentose phosphate pathway
 Produces precursor metabolites used in the synthesis of nucleotides, amino acids, and glucose (by photosynthesis)
o Entner-Doudoroff
 Glucose breakdown results in pyruvate (pyruvic acid), but different enzymes used
 Used by a few bacteria
• Pseudomonas aeruginosa, Enterococcus fecalis
 Produces precursor metabolites and NADPH
Fermentation – Anaerobic Respiration
 If oxygen unavailable:
• Lactic acid fermentation
o NADH produced in glycolysis, donates electrons to pyruvate, eventually producing lactate
 Recycles NAD+ necessary to accept hydrogen and electrons during glycolysis
• Alcohol fermentation
o NADH produced in glycolysis donates electrons to pyruvate, eventually producing ethanol
 Recycles NAD+ necessary to accept hydrogen and electrons during glycolysis
Post-Glycolysis Cellular Respiration
 Aerobic Cellular Respiration - metabolic oxidation of organic molecules to produce ATP, final electron acceptor is oxygen.
 C6H12O6 + 6O2 → 6CO2 + 6H2O + energy (mostly heat and ATP)
 Aerobic Respiration Pathways
 Pyruvate Oxidation
 Krebs Cycle
 Oxidative Phorphorylation in the Electron Transport Chain
 In eukaryotes, aerobic respiration takes place in mitochondria
 In prokaryotes, aerobic respiration takes place in the cell membrane
Pyruvate Oxidation
 CO2 is clipped from pyruvate (from glycolysis) forming Acetyl-CoA
o 1 NADH made per pyruvate (2 NADH total)
o Acetyl Co-A (2) enters into the Krebs cycle
Krebs Cycle or The Citric Acid Cycle
 Acetyl –CoA combines with oxaloacetate to form citrate (citric acid cycle)
o Oxaloacetate will be regenerated
o Glucose “remnant” continues to be oxidized, giving energetic electrons to coenzymes NAD+ and FAD+
o Per acetyl Co-A molecule (2 per glucose)
 3 NADH (6 NADH)
 1 FADH2 (2 FADH2)
 1 ATP via substrate level phosphorylation (2 ATP)
 4 molecules of CO2 are produced and exhaled
o The glucose molecule is completely consumed
 The energy extracted from glucose has been given to the coenzymes NAD+ and FAD+ to produce NADH and FADH2.
 NADH and FADH2 will carry energy to ETS where oxidative phosphorylation will occur
Electron Transport and Oxidative Phosphorylation
 Electron transport chain is a series of proteins/enzymes embedded in inner membrane of mitochondrion (eukaryotes) or cell membrane (prokaryotes).
o NADH and FADH2 carry electrons to ETC and drop them off
 NAD+ and FAD+ are regenerated to shuttle more electrons from the Krebs Cycle to ETC
o Energy from electrons is used to phosphorylate ADP à ATP in a process called oxidative phosphorylation
 oxidative phosphorylation – generation of ATP in which energy gained from electrons in electron transport chain is used to phosphorylate ADP à ATP
o Chemiosmotic Theory
 Energy gathered by ETC is used to pump H+
• Creates a H+ gradient
• H+ follow the concentration gradient through ATP synthase where ADP is phorphorylated to make ATP
Function of Oxygen in ETC
 Electrons added to beginning of ETC are passed along the proteins until they reach end.
• Electrons must be given away or ETC would stop
• Oxygen accepts electrons and combines with hydrogen to form water
• O2 + 4e- + 4H+ à2H2O
ATP Yield
 ATP formed by substrate level phosphorylation
o 2 ATP from glycolysis
o 2 ATP from Krebs Cycle
 ATP formed by oxidative phosphorylation
o For every NADH, 3 ATP are formed
o For every FADH2, 2 ATP formed
 2 NADH from glycolysis (2 x 3 = 6 ATP)
 2 NADH from pyruvate oxidation (2 x 3 = 6 ATP)
 6 NADH from Krebs Cycle (6 x 3 = 18 ATP)
 2 FADH2 from the Krebs Cycle (2 x 2 = 4 ATP)
 Grand Total = 38 ATP
o 2 ATP used to shuttle NADH from glycolysis
 Theoretical yield – 36 ATP formed per glucose molecule
Proteins can be catabolized to produce ATP
o Surplus amino acids are most often used to form ATP via deamination
 Deamination – removal of an amino group from a molecule
o NH2 is removed from amino acid, forming an organic acid (pyruvate, acetyl-CoA) and ammonia
 Ammonia is converted to urea and is excreted by kidneys
 Organic acid can be fed into aerobic respiration
Lipids yield more energy per unit weight than glucose or protein
 Lipolysis – fats hydrolyzed by lipase forming glycerol and fatty acids
• Acetyl CoAs from free fatty acids serve as a major energy source
• Beta – oxidation clips carbon units from fatty acid chains
o Carbon units are converted to Acetyl Co-A
o These products fed into Krebs Cycle
Photosynthesis
Plants, some protistans (algae and Euglenoids), and some bacteria
 Two steps in photosynthesis (both stages of photosynthesis occur in the chloroplast
o The light-dependent reactions convert light energy to chemical energy
 Pigment molecules like cholorophylls and carotenoids convert the light energy to chemical energy
 The energy is stored in ATP and NADPH (nicotinamide adenine dinucleotide phosphate).
o The light-independent reactions assemble sugars and other organic molecules using ATP and NADPH as energy sources
 Reactions take place in the stroma
 Carbon fixation takes place
 Glucose formation: 6CO2 + 12 H2O → light energy→ C6H12O6 + 6O2. + 6H2O
Two major types of organisms based on their acquisition of carbon
 Autotrophs
• Obtain carbon from CO2 in the air
 Heterotrophs
• Obtain carbon by catabolizing organic compounds
Two categories based on acquisition of energy
 Phototrophs
• Utilize light as energy source
 Chemotrophs
• Utilize chemical compounds as an energy source
• Energy obtained during cellular respiration (aerobic or anaerobic)
Four major groups that define how an organism obtains carbon and energy
 Photoautotrophs
• Use CO2 as a carbon source and light energy from the environment to make their own food
• Plants, algae, cyanobacteria, photosynthetic green sulfur and purple sulfur bacteria
 Chemoautotrophs
• Use CO2 as a carbon source but catabolize organic molecules for energy
• Hydrogen, sulfur, and nitrifying bacteria
 Photoheterotrophs
• Microorganism which requires light energy and gains carbon via catabolism of organic compounds
• Green nonsulfur and purple nonsulfur bacteria
 Chemoheterotrophs
• Microorganism which utilizes organic compounds for energy and carbon
• Most animals, fungi including yeasts, many protozoa, many bacteria
Categories based on Oxygen Requirements
o Obligate aerobes – require oxygen as a final electron acceptor of the electron transport chain
o Obligate anaerobes – cannot tolerate oxygen and uses a final electron acceptor other than oxygen
o Facultative anaerobes – can utilize fermententation or anaerobic respiration, but metabolism efficiency is lessened in the absence oxygen
 E. coli
o Aerotolerant aerobes – prefers anaerobic conditions but can tolerate exposure to low levels of oxygen
 Lactobacilli responsible for changing cucumber to pickles, milk to cheese
o Microaerophiles – require low levels of oxygen
 H. pylori
Nitrogen Requirements
o Growth –limiting nutrient
o Atmospheric nitrogen is not useful to most organisms
o Nitrogen fixation – the ability of some microorganisms to fix atmospheric nitrogen, reducing it to ammonia (a useable form of nitrogen)
Other Chemical Requirements
o Trace elements – elements required in very small amounts
 i.e. cobalt ,copper, manganese, molybdenum
 Serve as cofactors for some enzymes
o Growth factors
 Organic chemicals that cannot be synthesized by the microorganism
 i.e. amino acids, purines, pyrimidines, cholesterol
Temperature as a physical growth requirement
temperature affects the structure of proteins and lipids. Each organisms has an optimum temperature range and range of temperatures that it survives in
o Psychrophile – requires cold temperature of < 20oC
 i.e bacteria, fungi, algae living in snow, ice, cold water
o Mesophile – lives in temperatures from 20oC to 40oC
 Most human pathogens
o Thermophile – requires temperatures above 40oC
 Bacteria that live in hot springs
o Hyperthermophile – requires temperatures above 80oC
 Archaea
pH as a physical growth requirement
pH affects the structure of proteins and nucleic acids. Each organism has an optimum pH
o Neutrophile – grow best at neutral pH between 6.5 and 7.5
 Most bacteria and protozoa
o Acidophiles – grow in acidic environments down to pH 0
 Bacteria, many fungi
o Alkalinophiles – grow in basic environments up to pH 11.5
Physical Effects of Water
o Osmotic pressure
 Obligate halophiles – require high osmotic pressure such as exists in salt water
 Facultative halophiles – do not require, but tolerate salty conditions
o Hydrostatic pressure
 Barophiles – live in extreme pressure conditions deep in the ocean
Culturing Microorganisms
• Microorganisms cultured by transferring inoculum (sample) into a medium that contains nutrients
o Liquid media = broth
o Solid media = broth + agar
Culture
microorganisms that grow from an inoculum
Colony
culture that is visible on the surface of solid media
Clinical Sampling
sample from feces, saliva, csf, blood that is examined and tested for the presence of microorganisms
Pure Culture
consists of cells that arise from a single progenitor called a colony forming unit (CFU)
Isolation techniques for obtaining pure cultures
o Streak plate method – sterile inoculating loop is used to spread an inoculum across the surface of a solid medium in Petri dish
o Pour plate method – a series of dilutions separates CFUs and the final dilutions are mixed with warm agar in a Petri dish
Culture media
o Defined medium – precise chemical composition that supports the growth of a particular microorganism
o Complex media – contains several growth factors that support the growth of a variety of microorganisms
o Selective media – favors the growth of “wanted” microorganism and inhibit the growth of the “unwanted”
o Differential media – visible changes in the medium or the microorganisms growing on the medium differentiate microorganisms
o Reducing media – provide conditions conducive to growing anaerobes
Preserving cultures
o Refrigeration at 5oC sufficient for short-term storage
o Deep freezing between -50 to -95oC sufficient for long-term storage
o Lyophilization – freeze drying sufficient for long-term storage
Growth of Microbial Populations
• Binary fission – reproductive process in which a cell grows to twice its normal size, then divides in two, creating two daughter cells
• Logarithmic growth or exponential - describes how microbial population size increases (one cell divides into two, two cells divide into four, etc.)
Generation Time
• time required for a population of cells to double in number
o Many bacteria have a generation time of 1-3 hours
Growth Curve
• plots the number of bacteria growing in a population over time
o Lag phase – organisms adjust to their environment
o Log phase – population of organisms is most actively growing
o Stationary phase – new organisms are being produced at the same rate at which others are dying
o Death phase – organisms are dying more quickly than they are being replaced by new organisms
Measuring Microbial Growth
o Viable plate count – the size of the microbial population is estimated by counting the number of colonies formed when diluted samples are plated onto agar media
o Electronic counter – devices that count cells as they interrupt an electric current flowing across a narrow tube held in front of an electronic detector