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Microbiology
Test 2
| Question | Answer |
|---|---|
| What are the major macro elements? | Carbon (C), Nitrogen (N), oxygen (O), phosphorus (P), and sulfur (S) |
| What percentage of a cell's weight do macro molecules take up? | 95% |
| The 5 macromolecules are the elemental components of the macroelements of life. What are these macro elements? | nucleic acid, protein, lipid, carbohydrate |
| In what form are the macroelements magnesium (Mg), Calcium (Ca), Iron (Fe), and potassium (Fe) needed in the body? | Ionic form |
| In what quantity are the macroelements magnesium (Mg), Calcium (Ca), Iron (Fe) in the body? | milligram |
| What are the functions of the macro elements magnesium (Mg), Calcium (Ca), Iron (Fe) | heat resistance, enzyme activity, respiration, maintainance of ionic strength |
| What are the trace elements of bacterial nutrition? | Manganese (Mn), Zinc (Zn), Cobalt (Co),Molybdenum(Mo) Copper (Cu) and Nickel (Ni). |
| What quantity of a trace element is needed for bacterial nutrition? | Required in ug quantities per liter |
| What are trace elements required for? | enzyme function |
| What are the three classes of growth factors? | 1) purines and pyrimidines-nucleic acid 2) vitamins-usually used as enzyme cofactors 3) amino acid-protein |
| what are the nutritional types of organisms? | based on energy source or electron source |
| what energy source do phototrophs use? | light |
| what energy source do chemotrophs use? | obtain energy from oxidation of chemical compounds |
| what electron source do lithotrophs use? | use reduced inorganic substances |
| what is the electron source of organotrophs? | obtain electrons from organic compounds |
| what nutritional type do a majority of pathogens use? | chemoorganoheterotrophs |
| a majority of microorganisms are known as.... | photolithoautotrophs and chemoheterotrophs |
| What are sources of nitrogen? | organic molecules, ammonia, nitrate via assimilatory nitrate reduction, nitrogen gas via nitrogen fixation |
| What are deamination reactions? | reactions convert the nitrogen groups to ammonia which is then assimilated into biomass |
| What are 2 preformed forms of nitrogen? | organic nitrogen compounds such as amino acids or purines and pyrimidines |
| What is the most commonly used for of nitrogen by microorganisms | ammonia |
| How is NH4+ incorporated into glutamate when in high concentrations? | glutamate dehydrogenase |
| How is NH4+ incorporated into glutamate when in low concentrations? | glutamine synthetase system |
| Many bacteria can use _______as a sole nitrogen source | nitrate |
| What happens to nitrate during the assimilatory nitrate reduction process ? | it is reduced to ammonia |
| What nutritional form of phosphorous is used by most microorganisms? | phosphate (PO4+) |
| When used in a growth medium, how is phosphorous usually incorporated? | as a phosphate buffer system |
| What nutritional form of sulfur is used by most microorganisms? | sulfate (SO4+), which is then reduced |
| How is sulfur usually incorporated into growth mediums? | as a salt. a salt of ammonia (ammonium sulfate) or magnesium (Magnesium sulfate) |
| How is sulfur mainly used in relation to microorganisms? | to make the sulfur amino acids methionine and cystiene |
| "An organism that requires the same nutrients for growth as the majority of naturally occuring members of its species." What is this the definition of? | prototroph |
| What is a prototroph? | An organism that requires the same nutrients for growth as the majority of naturally occuring members of its species. |
| "A mutated prototroph that lacks the ability to synthesize an essential nutrient therefore must obtain it or a precursor from its surrounding environment." What is this the definition of? | auxotroph |
| What is an auxotroph? | A mutated prototroph that lacks the ability to synthesize an essential nutrient therefore must obtain it or a precursor from its surrounding environment. |
| How are culture media used in labratories? | need to grow, transport, and store microorganisms |
| What must a culture media contain? | all the nutrients required by the organism for growth |
| How are culture media classified? | -chemical constituents from which they are made -physical nature -function |
| In a culture media that uses a defined medium..... | All components of the medium are known and in a specific concentration. |
| minimal salts media are composed of... | the minimum growth requirements for a given organism |
| "Generally an organic rich medium of unknown composition" Which type of media does this describe? | complex media |
| Why are complex media routinely used? | allows fast growth and supports growth of many different organnisms |
| What is the complex media component "peptone" made up of? | protein hydrolysates prepared by partial digestion of various protein sources |
| What is the complex media component "extracts" made up of? | aqueous extracts, usually of beef or yeast |
| What is agar made up of? | sulfated polysaccharide used to solidify liquid media; most microorganisms cannot degrade it |
| What are the functional types of media? | supportive, enriched, differential, and selective |
| This type of media favors growth of a particular kind of organism and selects against others: eosin methylene blue, endoagar, MacConkey’s all used to detect enterics | selective media |
| Distinguishes between certain groups of bacteria by a color reaction with a dye or some other characteristics | differential media |
| Blood agar for hemolytic streptococcus is an example of what functional type of media? | differential media |
| What are cardinal growth temperatures? | For any given organism there is a minimum growth temperature, optimum growth temperature and maximum growth temperatures |
| What are 3 techniques for the isolation of pure cultures? | spread plate, streak plate, and pour plate are techniques used to isolate pure cultures |
| Who developed the isolation of pure cultures by the process of a population of cells arising from a single cell? | Robert Koch |
| What does the isolation of pure culture allow for? | the study of a single type of microorganism in a mixed culture |
| colony characteristics that develop when microorganisms are grown on agar surfaces aid in ___________ | identification |
| differences in growth rate from edges to center is due to (hint: 2 things) | -oxygen, nutrients, and toxic products -cells may be dead in some areas |
| What is a biofilm? | attached microbes that are members of a complex, slime enclosed community |
| Where can biofilms be formed? | any conditioned surface |
| when something is planktonic, it is__________ | free-floating microbes |
| What is formed when Microbes reversibly attach to conditioned surface and release polysaccharides, proteins, and DNA to form the extracellular polymeric substance (EPS) | a biofilm |
| What is produced when a biofilm matures and microbes reproduce? | additional polymers |
| In biofilms, what does the EPS and the change in the organisms physiology do? | protect microbes from harmful agents |
| What are some agents that could be harmful to microbes? | UV light, antibiotics, antimicrobials |
| What happens when biofilms form on medical devices, such as implants? | illness |
| What can biofilms sloughing off of organisms result in? | contamination of water phase above the biofilm, such as a drinking water system. |
| In what condition do extremophiles grow? | harsh conditions that would kill most other organisms |
| What is the optimum temperature of a mesophile? | between 20 and 45 degrees celcius |
| What is the optimum temperature range of a thermophile? | can grow at 55 degrees celcius. Optimum is between 55-65 |
| What is an example of a mesophile? | E. Coli, T. Vaginalis |
| What is the optimal temperature range for a hyper thermophile? | 85-110 degrees celcius |
| How do microbes reduce osmotic concentration of cytoplasm in hypotonic solutions? | mechanosensitive (MS) channels in plasma membrane allow solutes to leave |
| How do microbes fight hypertonic solutions? | increase internal solute concentration with compatible solutes to increase their internal osmotic concentration in hypertonic solutions |
| What are the optimal conditions for halophile growth? | grow optimally in the presence of NaCl or other salts at a concentration above about 0.2M |
| What are the optimal conditions for extreme halophile growth? | require salt concentrations of 2M and 6.2M and extremely high concentrations of potassium |
| why do extreme halophiles need high levels of salt and potassium? | cell wall, proteins, and plasma membrane require high salt to maintain stability and activity |
| why do extreme halophiles accumulate potassium? | remain hypertonic to the environment |
| what part of (extreme)halophiles requite large salt concentrations | Enzymes, ribosomes protein |
| how do halobacterium respond to a hypertonic environment? | increase ionic potassium concentration to 7M |
| When trying to battler a hypertonic solution, what are compatible solutes? | chemicals that can be kept at high concentrations without interfering with metabolism: glycerol, choline, betaine or proline and glutamate. |
| what us pH? | measure of the relative acidity of a solution negative logarithm of the hydrogen ion concentration |
| what is the optimal pH for acidophiles? | growth optimum between pH 0 and pH 5.5 |
| What is the optimal pH for neutrophiles? | growth optimum between pH 5.5 and pH 7 |
| What is the optimal pH for alkaliphiles(alkalophiles)? | growth optimum between pH 8.5 and pH 11.5 |
| Where on the spectrum do most microbes maintain their internal pH? | near neutrality |
| Why do most microbes maintain and internal pH near neutrality? | -the plasma membrane is impermeable to proton -exchange potassium for protons |
| How do microbes become acid tolerant? | -pump protons out of the cell -some synthesize acid and heat shock proteins that protect proteins |
| How do microorganisms change the pH of their habitat? | producing acidic or basic waste products |
| can microbes regulate their internal temperature | no |
| in what temperature range do proteins function best? | low temperatures |
| what part of the cell contains high levels of unsaturated fatty acids? | membrane |
| what type of thermophile can only grow about temperatures of 45 degrees celcius? | obligate |
| What is an example of an obligate thermophile? | Bacillus stearothermophilus. |
| What type of thermophiles can grow at temperatures lower than 45C but optimal is at 55C. | faciliative |
| what is an example of a facilitative thermophile? | Bacillus coagulans |
| What is an example of a hyperthermophile? | Pyrococcus abyssi. |
| how is the protein structure of thermophiles inherently heat stabilized? | more H bonds, more proline, chaperones |
| What stabilizes DNA? | histone like proteins |
| the membrane of thermophiles is stabilized by ? | more saturated, more branched and higher molecular weight lipids. Archaeal membranes also have ether linkages |
| These anaerobes prefer growing in the presence of oxygen but can grow anaerobically | faculative |
| What is an example of a faculative anaerobe? | E. Coli |
| these aerobes need at least 20% oxygen in their habitat to survive | obligate |
| This is an example of an oblligate aerobe | Azotobacter vinelandi. |
| these bacteria are damaged by 20% oxygen but require 2%-10% oxygen. | Microaerophilic |
| what are the protective enzymes produces by aerobes? | superoxide dismutase (SOD), catalase, peroxidase |
| superoxide radical, hydrogen peroxide, and hydroxyl radical are all examples of what developed when oxygen is reduced. what are they called? | reactive oxygen species (ROS) |
| all strict anaerobic microorganisms lack or have very low quantities of | superoxide dismutase and calatalse |
| anaerobes can be grown in 2 places within a labratory | work station with incubator or gaspak anaerobic system |
| how is oxygen sometimes toxic? | Toxicity is due to the formation of reactive oxygen molecules or compounds:1) superoxide (O2-); and 2)hydrogen peroxide (H2O2). These are both powerful oxidizing agents and damage proteins, nucleic acids and lipids. |
| how is superoxide formed? | Superoxide is formed during respiration by the univalent reduction of oxygen which occurs primarily via the reduced flavins of the respiratory chain |
| how is oxygen detoxified by the creation of superoxide? | Detoxification occurs through the action of the enzyme superoxide dismutase. 2 O2- + 2H+ ------superoxide dismutase--------> H2O2 |
| how is oxygen detoxified by the creation of hydrogen peroxide? | Hydrogen peroxide is formed primarily through the action of superoxide dismutase Detoxification occurs through the action of catalase 2 H2O2------- ------catalase---------------->2 H2O + O2 |
| why are strict anaerobes killed by oxygen? | Strict or obligate anaerobes lack or have very low levels of superoxide dismutase (SOD) and catalase and thus are killed by the presence of oxygen. |
| this is Obligate anaerobic spore forming rod gram positive bacteria. | c.diff |
| what is the significance of c.diff? | Cause of 3 million cases of hospital diarrhea and colitis (7% of admitted hospital patients per year). In the US 500K infections/15K deaths |
| what causes c.diff? | Cause- C. difficile releases 2 toxins, A and B. A is an enterotoxin and B is a cytotoxin. Both bind to receptors on the intestinal mucal cells compromising fluid absorption + retention |
| How does c.diff spread in hospitals? | Mechanism: Spores of bacteria prevalent in hospitals. Ingestion or surgical contamination of patient. Spores germinate in colon and colonize producing toxins. |
| how is c.diff treated? | Treatment. Usually Vancomycin or Metronidazole. Organism is very susceptible to this vancomycin. It is resistant to cephalosporins, ampicillin/amoxicillin, and clindamycin and aminoglycosides. |
| how do bacteria reproduce? | binary fission |
| what is the most important step in cytokinesis? | formation of the z ring |
| growth of microorganisms is measured by.... | population growth, increase in cell number, increase in cell size |
| when is a growth curve observed? | when microorganisms are cultivated in batch culture |
| how is a growth curve plotted? | as a partial logarithmic plot |
| what are the distinct phases of the growth curve? | lag, exponential, stationary, and death |
| What happens in the lag phase of the growth curve? | -No cell division occurs -Cells adjusting to medium and new environment (temp, nutrients, etc) -Synthesis of some new cell components -Varies in length depending on media shift, temperature shift and age of inoculum |
| What happens in the exponential or log phase of the growth curve? | -Bacteria are actively dividing at the maximum rate given their genetic potential, nature of medium and environmental conditions -Cells ar most uniform in terms of chemical and phsyiological properties. Log phase cells are commonly used experimentally |
| What happens in the stationary phase of the growth curve? | -No net increase in cell numbers thus growth curve levels off -Total number of viable cells is constant -Cell death may =cell division or the populations ceases to divide but remains metabolically active |
| what are some reasons for the stationary phase of the growth curve? | -Nutrient limitation -Toxic waste products -pH (usually becomes acidic) -Oxygen availability |
| What happens in the death phase of the growth curve? | -The detrimental changes resulting in the stationary phase worsen -Cells death is faster than cell division -It is a logarithmic function |
| what is the formula used for the exponential growth curve? | k=log10N1-log10N0 = log10N1-log10N0 (log10 2) x t (0.301) x t |
| what is the generation time for treponema pallidum? | 33 hours |
| how can microbial growth be measured? | changes in numbers of cells in a population and changes in mass of a population |
| how can bacteria cells be directly counted? | Petroff-Hausser counting chamber |
| how can large bacteria cells be directly counted? | hemocytometer |
| what are some characteristics of direct cell counting? | -Counts live and dead cells -Generally must have at least 106 cells per ml to see in high field -Quick and easy but takes practice to get reproducibility |
| how can live and dead cells be determined in membrane filtration? | with the use of dyes |
| how are cells visible in membrane filtration | floroscent dyes and dark background |
| what is a coulter counter? | electronic counter for larger eucaryote microorganisms like yeast, algae and protozoa |
| how does a coulter counter work? | Cell suspension passes through a small hole. An electric current flows across the hole and electrodes are placed on each side. Every time a cell passes through the electrical resistance increases and the cell is counted. Counts dead and live cells. |
| why is a coulter counter useful | fast, easy, accurate. used in hospitals to count white blood cells |
| what is flow cytometry? | microbial suspension forced through small orifice with a laser light beam specific antibodies can be used to determine size and internal complexity |
| this is the Most commonly used technique for growth curves or establishing a relationship between turbidity and cell numbers | viable counts |
| what are three common techniques for viable counts? | spread plate, pour plate, and membrane filtration |
| do viable counts count dead cells? | no |
| how long does it take for viable count results? | 24 to 48 hours |
| the number of cells in a viable count is determined by? | Nt= (CFU * dilution factor)/amount plated |
| how does the millipore membrane system work? | only molecules small enough to get through the pores of the filter, holes of 0.45mm, filtered, removed, incubated for 24 hours |
| What is the concept of measuring growth by turbidity? | Concept of measuring growth by turbidity is that microbial cells scatter light striking them. |
| How is turbidity measured? | Beer's Law-scattering of light is proportional to concentration of cells |
| what concentration of cells must be present to see turbidity? | 10^7 cells/mL |
| what is an instrument that measures light absorption that is more precise that a spectrometer? | nephelometer |
| What is the typical wavelength setting for a spectrometer? | 520-660 nm |
| At what point does Beer's law stop being functional for a spectrometer? | Beer’s law is obeyed only up to about 0.6 absorption units when using a spectrophotometer so if higher than that dilutions must be made. |
| Why is a nephelometer more accurate than a spectrometer? | Nephelometer measures light reflected at right angles. Klett-Summerson Nephelometer is specifically designed for measuring bacterial growth |
| When can cell number be made directly from turbidity? | when a viable count has previously been made in the exact same media |
| What is a mechanism in which the rate of incoming medium is equal to the rate of removal from the vessel | a chemostat |
| what is the limiting factor in a chemostat? | essential nutrients |
| what is the formula for a continuous culture? | D=f/v |
| "Process by which all living cells, spores, viruses and viroids are destroyed. Usually done by heat or gas autoclaves" is the definition of what? | sterilization |
| "Killing ,inhibition or removal of microorganisms on inanimate objects that may cause disease" is the definition of what? | disinfection |
| "prevention of infection by use of chemicals on living tissue" is the definition of what? | antiseptis |
| what do statics do? | prevent growth |
| what do cides do? | kill |
| "reduction of microbial population to levels deemed safe (based on public health standards)" is the definition of what? | sanitation |
| "prevention of infection of living tissue by microorganisms" is the definition of what? | antiseptis |
| What are antiseptics? | chemical agents that kill or inhibit growth of microorganisms when applied to tissue |
| What are the factors that determine the effectiveness of agents in microbial death? | Factors influencing the effectiveness of agents: 1) population size; 2) population composition; 3) concentration or intensity of chemical or physical agent; 4) duration of exposure; 5) temperature; 6) local environment |
| how does killing biofilms compare to killing other microbes? | organisms in biofilms are physiologically altered and less susceptible to many antimicrobial agents |
| what are the methods of sterilization? | autoclave, gamma or ion radiation, membrane filtration |
| what are the characteristics of the autoclave? | Moist Heat under pressure: The autoclave. 121C at 15 lb psi is the standard for small volumes of liquid. Larger volumes take longer |
| how is air filtered? | surgical masks, HEPA, cotton plugs on culture vessels |
| Why moist heat in autoclave? | -destroys viruses, fungi, and bacteria -boiling will not destroy spores and does not sterilize -degrades nucleic acids, denatures proteins, and disrupts membranes |
| how is the quality of steam sterilization tested? | quality control - includes strips with Geobacillus stearothermophilus |
| what does dry heat sterilization do? | denature proteins and oxidize cell contituents |
| how long and at what temperature must items be sterilized using dry heat sterilization? | 2-3 hours at 160 to 170 degrees celcius |
| how is filtration sterilization used? | filter microbials in air and Sterilizes solutions of heat-sensitive materials by removing microorganisms |
| what wavelength is best for sterilization using ultraviolet radiation? | 260 |
| how does UV radiation work for sterilization? | Causes thymine dimers preventing replication and transcription |
| what is UV radiation used to sterilize? | UV limited to surface sterilization because it does not penetrate glass, dirt films, water, and other substances Has been used for water treatment |
| How is ionizing radiation used? | used for sterilization and pasteurization of antibiotics, hormones, sutures, plastic disposable supplies, and food |
| What does ionizing radiation destroy? | destroys bacterial endospores; not always effective against viruses |
| What is particularly useful about gamma radiation? | gamma radiation penetrates deep into objects |
| What is an example of a sterilizing gas? | ethylyene oxide (EtO) |
| How does ethylene oxide kill? | It kills by combining with proteins and can penetrate packing material like plastic wrap. |
| what are sterilizign gases useful to sterilize? | Good for sterilizing plastics, heart lung machine components, sutures and catheters |
| Why my EtO be mixed with carbon dioxide? | EtO is very toxic and explosive so usually mixed at 10-20% with CO2 |
| What is the pasteurization process? | Pasteurization-Process of heating milk and other liquids to destroy microorganisms that can cause spoilage or disease. |
| What was the old method of pateurization? | 63C for 30 minutes |
| What is the new method of pateurization? | New Methods include flash pasteurization or high temperature short term (HTST). 72C for 15 seconds with rapid cooling. |
| What are phenols and what do they do? | Commonly used in hospitals. Lysol is a penolic.These agents denature proteins and disrupt membranes |
| What are alcohols and what do they do? | Alcohols: Ethanol, isopropanol. Used at 70%. Denature proteins |
| What are halogens and what do they do? | Halogens:fluorine, iodine, chlorine. Uusally at 1-2%. Strong oxidizing agents and react with many proteins. |
| What are detergents and what do they do? | Detergents: Both anionic and cationic are organic wetting agents that disrupt cell membranes. |
| what are aldehydes and how do they act as sporocides? | Aldehydes such as formaldehyde and gluteraldehyde. React with DNA and proteins and inactivate. Sporicidal. |
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