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Closed System
No nutrients added later and no wastes removed
Lag, Exponential, Stationary, and Death
List the 4 growth phases in microbial growth curve
Lag phase
adjustment period where there is initially no cell division
Exponential (log) phase
time of max growth that is limited almost exclusively by the organism's reproductive potential
Stationary phase
Period where the growth rate declines to where the death rate is more or less equal to the reproductive rate
Death phase
The nutrients are depleted or the medium becomes toxic to the organism which causes a decline in the population
Continuous culture
an open system in chemostat, maintains a continuously growing microbial culture at exponential phase, supplies fresh nutrients continually, removes waste and products continually and is used in industries to extract useful primary metabolites, including amino acids, organic acids, etc.
Bioluminescence
Emission of light by living organisms, often gram neg rods, only occurs in presence of O2 and when population density has reached a certain threshold, requires enzyme lucifase and FMNH2
Quorum Sensing
The ability of bacteria to regulate gene expression based on density of cells
Fluorescence
To emit light of a different color than the light that is being received
Differentiate based on fermentation or oxidation of sugars; uses bromothymol blue to indicate pH change, uses mineral oil, green/blue shows no oxidation, while yellow shows oxidation, used to separate Enterobacteriaceae from Pseudomonas and Alcaligenes
Oxidation-Fermentation Test
Differentiate based on fermentation of specific carbohydrates to separate members of Enterobacteriaceae from other gram neg rods; phenol red is indicator, has tube to catch gas bubbles, acid produced turns yellow, gas produced gets bubble, turns pink is alkaline due to peptone degradation
Phenol Red Broth (Carbohydrate fermentation test)
Amylase is used to hydrolyze polysaccharides, done on petri dish, uses iodine, clearing around bacteria indicates amylase is present
Starch Hydrolysis (Amylase Test)
Casein is milk protein and a source of amino acids for organisms that can hydrolyze it, casease hydrolyzes casein, clearing around growth indicates casease is present
Casein Hydrolysis
Gelatin is protein derived from connective tissue in animals, gelatinase serves as collagenase and allows organism to be more invasive if infecting an animal; done in slant, if liquified, gelatinase is present, if still solid, gelatinase is negative
Gelatin Hydrolysis
Urea is product of decarboxylation of amino acids, hydrolyzed to ammonia and CO2 by urease; done in test tubes, read at 24 hours, uses phenol red as indicator, will turn pink if urease is positive, yellow or brown if negative for urease
Urea Hydrolysis (Urease Test)
include Indole, Methyl Red, Voges Proskauer, Citrate, and differentiate members of Enterobacteriaceae and distinguish them from other Gram neg rods
IMViC tests
Differentiation of enterobacteriaceae, salmonella, and shigella; uses Kovac's reagent with indole to form red color, sulfur reduction has occurred if solution turns black, red layer in alcohol top layer if organism produces tryptophanase and hydrolyzes tryptophan into indole and pyruvate; murky growth radiating out from stab means motility
Indole Test using SIM medium
Tests for mixed acid fermentation, uses methyl red dye to test pH which is red at 4.4 but yellow above 6.2 on pH scale; red color is positive for mixed acid fermentation
Methyl Red test
Tests for conversion of glucose products to acetoin and 2,3-butenadiol; reagents react with acetoin to form diacetyl, which reacts with guanidiine nuclei from peptone to produce red color, which is the positive result color, can take 1 hour
Voges-Proskauer test
Citrate is component of Krebs cycle, sodium citrate only carbon source, ammonium phosphate only nitrogen source, only cells that have citrate-permease will grow, uses bromothymol blue which turns from green to blue as pH goes up, blue color is a positive result for citrate, green is negative
Citrate Slant
Tests for Nitrate reductase which reduces nitrate (NO3) to nitrite (NO2), use durham tubes to collect any gases made, any gas initially made means nitrate reduction has occurred; then add reagents, if it turns red, positive for nitrate reduction; if not add zinc to remaining tubes, here red color means negative result for nitrate reduction
Nitrate Reduction Test
Detects the presence of catalase which protects cells from hydrogen peroxide; differentiates Staph and Micrococcus from Strepto, entero, and lactococcus; if bubbles are present, it is positive for catalase
Catalase test
Tests for presence of cytochrome C oxidase, uses oxidase reagent, dark blue/purple within 20 seconds indicates that cytochrome C oxidase is present, no color change means no cytochrome C oxidase
Oxidase test
Found in S. aureus that makes it resistant to antimicrobials and body's immune response, most staph species don't produce coagulase, makes fibrin barriers around bacterial cells which prevents phagocytosis; tube test detects presence of either bound or free coagulase, if medium is solid within 24 hours, it is positive for coagulase; slide test only detects bound coagulase, if there is clumping, cells are positive for coagulase
Coagulase Test
Tests for Staphylococcus aureus, uses coagulase test, if positive for coagulase it is S. aureus, if negative for coagulase, it is S. epidermis
Rapid Staph test
Take throat swab, if two reddish-purple colored lines, it is positive for strep, if only one colored line, then it is negative for strep
Rapid Strep test
Sterilization
any process that kills or destroys all forms of life, including bacterial endospores, usually achieved by physical methods
Disinfection
any process that reduces a microbial population on an inanimate surface to an acceptable level, achieved using a disinfectant, usually a chemical
Antisepsis
any process that reduced a microbial population on living tissue to an acceptable level, achieved using an antiseptic, usually a chemical
-cidal
suffix used to identify agents that kill or destroy microorganisms
-static
suffix used to identify agents that do not kill, but only inhibit the growth of microorganisms
Dry Heat
kills organisms by oxidizing proteins and lipids, need high temps and long heating times such as 160 C for 2 hours, used for glassware and metal objects
Moist Heat
also called autoclaving, denatures proteins and membrane lipids, uses steam under pressure, uses 121 C at 15 psi for 15 min
Non-ionizing radiation
UV light, is used for disinfection or sterilization, induces formation of thymine dimers, effective between 290-220 nm and is optimal at 260 nm
Ionizing radtions
using x-rays or gamma-rays and is used for sterilization, induces double stranded breaks in DNA that cannot be repaired, effectiveness is proportional to amount of DNA, good penetrating power and can be used to sterilize prepackaged items
Filtration
uses filters (0.45 or 0.22 um pore size) to physically remove microorganisms from a liquid solution
Chemotherapeutic agent
A chemical that interferes directly with the proliferation of microorganisms at concentrations tolerated by the host
Antibiotic
A type of chemotherapeutic agent that may be naturally occurring or chemically synthesized. Naturally occurring antibiotics are primarily produced by sporulating organisms at the time of sporulation. However, once identified the antibiotics may be chemically modified to alter their effectiveness.
Antimycotics
kill or inhibit the growth of fungi
Antivirals
inhibit the replication of viruses within the host cells
0.5 McFarland standard, agar plate swabbed 3 different directions, place disks evenly across the surface
Kirby Bauer Method
Bacitracin interferes with synthesis of peptidoglycan which inhibits bacterial cell wall synthesis, any zone of inhibition 10 mm or greater is interpreted as being bacitracin susceptible, used to differentiate B-hemolytic, group A streptococcus pyogenes from other B-hemolytic streptococci
Bacitracin Susceptibility test
Novobiocin interferes with ATPase activity, should produce zone of inhibition 16 mm or greater, used to differentiate coagulase negative staphylococci, most often used to identify staph saprophyticus, a common cause of UTIs in women
Novobiocin Susceptibility test
interferes with ATPase activity and ATP production, 14 mm zone of inhibition, differentiates strep pneumoniae from other a-hemolytic sprep, as s. pneumoniae is the only strep susceptible to optochin
Optochin Susceptibility test