Bacteria classified to grow at higher temperatures but capable of growing at low temperatures
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Prodigiosin
A red pigment and antibiotic
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Oxygen
Makes up 21% of Earth’s atmosphere
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Strict (Obligate) Aerobes
Bacteria that must grow in oxygen
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Why Aerobes Must Grow in Oxygen
Their metabolism requires oxygen and they carry out respiration in which oxygen is used as the terminal electron acceptor in the electron transport chain
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Microaerophiles
Aerobic bacteria that prefer 2-10% oxygen
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Why Microaerophiles Prefer Less Oxygen
The lower oxygen concentration is necessary for their respiratory metabolism
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Facultative Anaerobes
Bacteria that grows well in aerobic conditions but can also grow anaerobically when oxygen is not available
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Why Can Facultative Anaerobes Grow in Both Conditions
Their flexible metabolism allows them to produce energy by carrying out respiration in aerobic conditions or fermentation in anaerobic conditions
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Aerotolerant Anaerobes
Anaerobes that can tolerate oxygen and grow in its presence, but do not require it for energy production
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Why Aerotolerant Anaerobes Do Not Need Oxygen
They only use fermentation to produce energy
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Strict (Obligate) Anaerobes
Bacteria that are harmed or killed by oxygen and produce energy through fermentation
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Why Strict Anaerobes Need Aerobic Conditions
They lack the systems that can convert toxic forms of oxygen to less harmful compounds that will not damage the cell
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Fermentation
Inorganic compounds (such as nitrates and sulfates) take the place of oxygen in the electron transport chain as the terminal electron acceptor
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Toxic Forms of Oxygen
Hydrogen peroxide and superoxide
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H2O2 and Superoxide
Can damage biological molecules (such as nucleic acids, proteins, and coenzymes)
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Catalase
Degrades hydrogen peroxide to oxygen and water
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Peroxidase
Degrades hydrogen peroxide
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Superoxide Dismutase
Convert superoxides to oxygen and hydrogen peroxide
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FTM
Fluid Thioglycollate Medium
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Fluid Thioglycollate Medium
A rich medium that supports the growth of both aerobic and anaerobic bacteria
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FTM Composed of
Glucose, cystine, and sodium thioglycollate (to reduce its oxidation/reduction potential)
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FTM Contains
Resazurin
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Resazurin
A dye that turns pink in the presence of oxygen (and an oxygen indicator)
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Brewer’s Anaerobic Agar
A solid medium for cultivating anaerobic bacteria
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Brewer’s Anaerobic Agar Contains
Thioglycollate and Resazurin
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Thioglycollate
A reducing agent
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Antiseptics and Disinfectants
Chemical agents that are used to control microorganisms
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Antiseptics
Substance that inhibit microbial growth or kill microorganism but are gentle enough to be applied to living tissue; do not destroy endospores
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Disinfectants
Chemical agents that are applied to inanimate objects to kill microorganisms (too harsh for living tissue)
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Disinfectants Classified as Sterilants or Sporocides
Destroy all microbial life, including endospores
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Sanitizers
Agents that reduce microbial numbers to a safe level but do not completely eliminate all microbes
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Bacteriostatic
An agent that inhibits the growth of bacterial cells but does not kill them (when removed, the growth resumes)
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Bactericidal
Agents that kill bacterial cells
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Psycrophiles Location
Icy waters of the Arctic and Antarctic
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Mesophiles Extra
Most bacteria; Most pathogens grow between 35 and 40 degrees
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Thermophiles Location
In soils where midday temps can reach greater than 50 degrees or in compost piles where temps exceed 60 to 65 degrees
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Hyperthermophiles Location
Isolated from thermal vents in the ocean floor or volcanic heated hot springs
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Examples of Pychrotrophs
Proteus, Pseudomonas, and Leuconostoc (mesophiles in fridges→food spoilage) & Listeria monocytogenes and Campylobacter (foodborne pathogens)
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Enzymes Above Maximal Temperatures
Denature and lose activity
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Enzymes Below Minimal Temperatures
Chemical activity slows down
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As Temperature Drops
Transport of nutrients into the cell decreases and membrane fluidity changes
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As Temperatures Rise
Membrane lipids can be destroyed resulting in serious damage to the membrane and death of the organism
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Ribosomes
The energy centers of cells
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Ribosomes in High Temps
Cease to function adequately
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S. marcescens
Produces prodigiosin in a certain temperature range
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Examples of Strict Aerobes
Pseudomonas, Micrococcus, and Bacillus
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Helicobacter pylori and Campylobacter
Pathogens found in the human gastrointestinal tract (microaerophiles)
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Examples of Facultative Anaerobes
E. coli and Salmonella
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Examples of Aerotolerant Anaerobes
Streptococci (produces cheese, yogurt, and sour cream) and Streptococcus pyogenes (causes strep throat)
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Examples of Strict Anaerobes
Clostridium
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Strict Anaerobes Location
Soil, rumen of cattle, and septic systems
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Pink of the FTM
Top of the medium
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Colorless of the FTM
Middle and bottom of the medium
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FTM Agar
A small amount is added to the medium to localize the organisms and favors anaerobic conditions in the bottom of the tube
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GasPal
Capable of producing hydrogen, placed in an anaerobic jar to form water from the present oxygen
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Anaerobic Indicator Strip
Used to make certain the anaerobic jar is an oxygen-free environment which is checked by being colorless in anaerobic conditions and blue in the presence of oxygen
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Two Common Antibiotics
Penicillin and streptomycin
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MRSA
Methicillin-resistant S. aureus
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HAI
Health-care acquired infections
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Antimicrobial Agents
Can vary their effectiveness against various pathogenic bacteria
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Narrow Spectrum Antimicrobial Agents
More effective against gram positive bacteria OR gram negative bacteria
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Broad-Spectrum Antimicrobials
More effective against both kinds of organisms
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Broad vs Narrow Spectrum
Depends on mode of action, ability to be transported into the cell, and permeability
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Antimicrobials Can Target
\-Cell wall synthesis
\-DNA and RNA synthesis
\-Protein synthesis
\-Vitamin Synthesis
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Gram Negative Bacteria
The outer membrane acts as a permeability barrier and can restrict antimicrobial access
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Zone of Inhibition
The zone around the disk where no growth occurs due to the agent inhibiting or killing the organism
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Zone Can Vary With
\-Diffusibility of the agent
\-Size of the inoculum
\-Type of medium
\-Etc.
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Inoculation in the Kirby-Bauer Method
Made with a cotton swab from broth culture
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Kirby-Bauer Method
A way to determine the sensitivity or resistance of a bacterium to an antimicrobial that is standard, reliable, simple, and fast
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Kirby-Bauer Method Procedure
Performed by uniformly streaking a standardized inoculum of the test organism on Mueller-HInton medium, and then paper disks containing specific concentrations of an antimicrobial or antibiotic are deposited on the agar serface
Studied by 114 people
