Above 100° C (212°F) most bacteria Multiple Choice are destroyed. stop growing, but are not dead. are not affected by the heat. grow rapidly.
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Which of the following statements is the most correct? Select one: a. None of the other answers are correct. b. Bacteria cannot live in hot environments. c. All bacteria can live in hot environments, but some live better at colder temperatures. d. Body temperature is the optimum temperature for all bacteria. e. All of these answers are correct. f. The temperature ranges for enzyme performance dictate the temperature the bacteria can grow.
Sri K.
1) Answer parts a through VV. a) The scientist that contributed most to the development of pure culture techniques was Alexander Fleming. Louis Pasteur. Edward Jenner. Robert Koch. b) The solidifying agent used most successfully in bacterial nutrient media is gelatin. peptone. agar. starch. c) Prokaryotic cells divide by a process known as conjugation. mitosis. binary fusion. binary fission. d) In nature, bacteria often grow in close association with many other kinds of organisms. may remain in a prolonged exponential phase. frequently synthesize structures such as slime layers. may adhere to surfaces by means of pili and slime layers. All of the choices are correct. e) The simplest technique for isolating bacteria in growth media is referred to as the pour plate method. streak plate method. serial dilution method. MPN method. f) Bacteria may be stored on a slant in the refrigerator. frozen in glycerol solution. lyophilized. in broth at 37°C. on a slant in the refrigerator, frozen in glycerol solution AND lyophilized. g) In the growth curve of a bacteria population, the bacteria are rapidly increasing in number in the lag phase. exponential (log) phase. stationary phase. decline phase. boomer phase. h) During which phase of growth are bacteria most susceptible to antibiotics? lag stationary exponential (log) decline i) When doing experiments with bacteria it is usually not necessary to standardize which stage of growth is used. it is best to use colonies as all the bacteria in a colony are at the same stage of growth. it is best to use bacteria from the same stage of growth. the age of the bacteria is not important. j) During which phase of the bacterial growth curve does the total number of viable cells decline? stationary lag exponential death k) The lag phase of the bacterial growth curve is marked by a decrease in cell mass. dormant, metabolically inactive cells. metabolically active cells. vigorously dividing cells. l) During which phase of the bacterial growth curve does a bacterial population become much more resistant to harmful conditions? lag phase exponential phase stationary phase late log phase m) In a rapidly multiplying bacterial population, cell numbers increase arithmetically. logarithmically. linearly. indirectly. n) Generally the proteins of thermophiles resist denaturation. react more efficiently with DNA. are easily denatured. have a particular amino acid sequence that restricts bond formation. are easily denatured AND have a particular amino acid sequence that restricts bond formation. o) A hot tub (approx. 104 deg. F or 40 deg. C) would most likely contain psychrophiles. partiers. thermophiles. mesophiles. p) The optimal temperature for most human pathogens might be expected to range from 35-40°C. 20-45°C. 15-25°C. 93-98.6°C. q) Mycobacterium leprae is typically found infecting the ears, toes and fingers of its host due to its requirement for well-oxygenated blood. easy access to those parts. need for cooler temperatures. long incubation period. r) Organisms that require gaseous oxygen for metabolism are referred to as facultative aerobes. obligate aerobes. facultative anaerobes. microaerophiles. s) Organisms that are indifferent to the presence of oxygen and do not use it are aerotolerant anaerobes. facultative anaerobes. obligate aerobes. microaerophiles. t) Shake tubes are used to determine the pH requirements for bacterial growth. temperature requirements for bacterial growth. oxygen requirements for bacterial growth. salt requirements for bacterial growth. u) The optimum pH for growth of most species of bacteria is pH 5. pH 7. pH 9. pH 6. v) High concentrations of salt and sugar in foods are useful in preserving the food. tend to draw water out of a cell. tend to force water into a cell, causing plasmolysis. have no effect on water availability. are useful in preserving the food AND tend to draw water out of a cell. w) Small organic molecules that must be provided to bacteria in order for them to grow are called minerals. growth factors. water. vitamins. x) Organisms that use organic molecules as their source of carbon are called chemotrophs. organoheterotrophs. heterotrophs. autotrophs. y) Organisms that use CO2 as their source of carbon are called organotrophs. heterotrophs. autotrophs. chemotrophs. z) Chemoheterotrophs use sunlight as an energy source. use pre-formed organic molecules as a carbon source. use pre-formed organic molecules as an energy source. use inorganic chemicals as an energy source. use pre-formed organic molecules as a carbon source AND as an energy source. A) Medically important bacteria are often grown on agar containing blood. grown at 37°C. grown on agar containing chocolate. grown at a pH of 5. grown on agar containing blood AND grown at 37°C. B) Products which limit pH changes are often incorporated into media and are referred to as enzymes. bases. buffers. acids. C) A medium that inhibits the growth of organisms other than the one being sought is termed a(n) synthetic medium. specific culture medium. selective medium. enrichment medium. D) It is assumed that every colony observed on a streak plate arose from a single bacterium. True False E) In microbiology, growth usually refers to an increase in size of the bacteria. True False F) There are 5 stages of growth in an open system of culture. True False G) A single bacterial cell may multiply to form a visible colony. True False H) Freezing is an effective means of destroying bacteria. True False I) Lister developed his ideas on prevention of infection during medical procedures after studying the work of Koch. Pasteur. Jenner. Fleming. J) One of the first chemicals used by Lister to prevent surgical infections was alcohol. iodine. carbolic acid. mercury. K) The process of killing or removing all of the microorganisms in or on a material is termed sterilization. disinfection. sanitation. antisepsis. L) A sterile item is free of viable microbes. endospores. viruses. prions. microbes, endospores AND viruses. M) A suffix used to describe a killing action would be -static. -cidal. -cillin. -tion. N) Pasteurization is the use of heat to sterilize food products. is the use of heat to reduce numbers of pathogenic/spoilage bacteria in a food item to a safe level. is a process which uses intense cold to kill microorganisms on foods. is a process which uses short bursts of radiation to kill microorganisms on foods. O) Plain soap is very effective in controlling spread of microorganisms because it is bacteriostatic. very effective at the mechanical removal of microorganisms. virucidal. bactericidal. P) Nosocomial infections are acquired at various social events. are acquired while in the hospital. occur because of a susceptible population and presence of disease causing organisms. are acquired at sporting events. are acquired while in the hospital AND occur because of a susceptible population and presence of disease causing organisms. Q) To reduce or eliminate disease/spoilage causing organisms, food is often subjected to heat. chemical additives. radiation. cold. All of the choices are correct. R) Microbial death rates may be affected by pH. temperature. the presence of organics. All of the choices are correct. S) Moist heat kills microorganisms by irreversible coagulation of proteins. destruction of carbohydrates in the cell wall. denaturation of nucleic acids. dissolving the capsule. T) Boiling is not reliable for sterilization because heat sensitive instruments may be destroyed. heat resistant endospores are unaffected. water boils at a higher temperature at lower altitudes. viruses are more sensitive to heat than bacteria. U) Which are essentially equivalent treatments? dry 200°C heat for 1.5 hours; wet 121°C heat for 15 minutes dry 160°C heat for 1.0 hour; wet 200°C heat for 30 minutes dry 121°C heat for 1.5 hours; wet 200°C heat for 15 minutes dry 100°C heat for 2.0 hours; wet 100°C heat for 30 minutes V) Which of the following is not a sterilization method? hot air oven autoclave pasteurization filtration W) The autoclave treatment may be monitored by heat-sensitive tape. heat-resistant endospores of Geobacillus stearothermophilus. pressure indicators alone. waiting for contaminants to appear on freshly poured media. heat sensitive tape AND heat-resistant endospores of Geobacillus stearothermophilus. X) Commercial canning processes are geared to destroy Clostridium botulinum spores. kill all endospores. are especially needed on low acid foods. are 12D processes (designed to kill 1012 endospores). are geared to destroy Clostridium botulinum spores, are especially needed on low acid foods, AND are 12D (designed to kill 1012 endospores) processes. Y) Generally, membrane filters are not used to remove bacteria from liquids. microorganisms from gases. spoilage agents from alcoholic beverages. enzymes. Z) Gamma irradiation has not been approved for use on food. can be used to either sterilize or pasteurize, depending on the dose of radiation. leaves some radioactive particles in the treated substance. usually kills by disrupting cell membranes. AA) Ultraviolet radiation at the bactericidal wavelength destroy bacteria by destroying endospores. damaging nucleic acid. preventing spore formation. denaturing proteins. BB) Microwaves do not kill organisms directly but kill by the heat they generate in a product. generating free radicals. generating toxins. creating thymine dimers. CC) Alcohols are not reliably effective at destroying vegetative bacteria. enveloped viruses. naked viruses. endospores. naked viruses AND endospores. DD) Glutaraldehyde is, if given enough time, able to destroy all forms of microbial life. is very good for use on heat-sensitive medical items. attacks lipids. does not affect naked viruses. is, if given enough time, able to destroy all forms of microbial life AND is very good for use on heat-sensitive medical items. EE) Chlorhexidine is a member of the biguanides. is extensively used in antiseptics. is ineffective against vegetative bacteria. is limited in use due to its high toxicity. is a member of the biguanides AND is extensively used in antiseptics. FF) Ethylene oxide is gas that is very useful for sterilizing heat or moisture sensitive items. is potentially carcinogenic. is used as a 37% aqueous solution. is effective against all microorganisms except endospores and viruses. is very useful for sterilizing heat or moisture sensitive items AND is potentially carcinogenic. GG) Which is true of iodine? It does not readily kill endospores. It may be used as an antiseptic or as a disinfectant. It is important to use it at the recommended dilution. It is usually found as tinctures or iodophors. All of the choices are true. HH) Which of the following is true of hydrogen peroxide? It is a sterilant for inanimate objects and is quickly inactivated on living tissue. It leaves a toxic residue. It is broken down by catalase into water and oxygen. It is even more effective when used in combination with peracetic acid. It is a sterilant for inanimate objects and is quickly inactivated on living tissue; it is broken down by catalase into water and oxygen AND it is even more effective when used in combination with peracetic acid. II) Phenolics denature proteins and destroy cytoplasmic membranes. remain effective in the presence of detergents or organic material. such as triclosan, have been used widely in various lotions and soaps. reliably inactivate all groups of viruses. denature proteins and destroy cytoplasmic membranes, remain effective in the presence of detergents or organic material, AND phenolics such as triclosan, have been used widely in various lotions and soaps. JJ) Quaternary ammonium compounds are cationic detergents which help wash surfaces. attracted to the negative charge on the microbial cell surface. used as a 37% aqueous solution. very effective against Pseudomonas. cationic detergents which help wash surfaces AND attracted to the negative charge on the microbial cell surface. KK) Silver sulfadiazine, a combination of silver and a sulfa drug, is used to disinfect water for drinking. prevent infection of surgical wounds. prevent infection of second- and third-degree burns. counteract lead poisoning. treat bites from werewolves. LL) Prions and viroids are easily destroyed by common sterilization procedures. True False MM) Upon heat treatment, bacteria die at a constant proportion. True False NN) The more bacteria one starts with, the longer it will take to kill them all. True False OO) Heat treatment is an effective method for sterilization or disinfection of all materials. True False PP) Boiling is very effective at removing most common waterborne pathogens. True False QQ) Dry heat takes a much shorter time to sterilize material than wet heat. True False RR) Hydrogen peroxide may be used as a sterilant on living tissue. True False SS) Organic acids, such as benzoic acid, are often added to foods to prevent microbial growth. True False TT) Which of the following organisms are resistant to destruction by typical control methods? endospores of Bacillus and Clostridium Pseudomonas naked viruses Mycobacterium spp. All of the choices are correct. UU) A common environmental organism that may even grow in certain chemical disinfectants is Escherichia coli. Streptococcus pneumoniae. Pseudomonas aeruginosa. enveloped virus. VV) Upon treatment with heat or chemicals, bacteria will all die immediately. die at a constant proportion. die at an exponential rate. die at a geometric rate.
8.) What happens to an organism at a temperature above the maximum growth temperature? a.) The membrane loses its fluidity. b.) Proteins denature. c.) Metabolic activity slows down. d.) Two of these are correct. 9.) Organisms that grow best in basic pH ranges are called ___. a.) Neutrophiles. b.) Acidophiles. c.) Basophiles. d.) Alkaliphiles. 10.) Hypotonic conditions can cause cells to ___. a.) Shrink. b.) Burst. c.) Swell. d.) Two of these are correct.
Anand J.
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