1) Quorum sensing is used by bacterial cells to determine which of the following? a) the size of the population b) the availability of nutrients c) the speed of water flow d) the density of the population 2) Which of the following statements about autoinducers is incorrect? a) They bind directly to DNA to activate transcription. b) They can activate the cell that secreted them. c) N-acylated homoserine lactones are autoinducers in gram-negative cells. d) Autoinducers may stimulate the production of virulence factors. 3) Which of the following statements are NOT true of Quorum Sensing? a) occurs only at a high cell density b) always involves an acyl-­homoserine lactone c) allows coordination of bacterial functions d) is mediated by a diffusible signaling molecule 4) Which of these are considered emergent properties of biofilms? a) Cell-cell signaling b) Cell division (binary fission) c) Complex architecture (e.g. Towers, mushrooms etc). d) Altruism e) 5) Which of these phenomena are known to be under the control of Cell-cell signaling? a) Bioluminescence or the production of light by Vibrio fisheri in the light organs of certain marine fish. b) The formation of complex architecture in biofilms. c) The synthesis of virulence factors, such as toxins, in certain pathogens. d) Multicellularity in bacteria. 6) Biofilms have been shown to be very resistant to antimicrobial materials like disinfectants and antibiotics. Which among the following are believed to be significant factors responsible for this resistance? a) The cells are relatively metabolically inactive (metabolically quiescent) due to nutrient limitation. These inactive cells provide few points of attack for antimicrobials. b) The biofilm matrix serves as a barrier to the diffusion of antimicrobials and thus prevents killing of biofilm cells. c) In biofilms genes for defensive mechanisms such as enzymes that pump antimicrobials out of the cell (efflux pumps) are up-regulated and this may protect the cells. d) Some believe that some biofilm cells (Persister cells) produce proteins that inactivate critical cellular functions such as translation, transcription and DNA replication. These "toxins" force this small population of cells into a dormant state with resists killing by antimicrobials. Later, after an antimicrobial challenge, other proteins (antitoxins) may inactivate the toxins permitting growth to resume. 7) Coliform bacteria: a) Grow in the intestines of people and warm blooded animals b) Usually cause diseases c) Respond to water treatment differently than do most other pathogens d) Exist only in water that contains pathogens e) All of the above 8) Following are types of microorganisms that can be pathogenic (disease producing) in drinking water: a) Bacteria b) Protozoa c) Viruses d) a and c e) All of the above 9) The single most important consideration about any drinking water supply is its freedom from: a) Iron staining b) Disease-producing organisms c) Total dissolved solids d) Chlorides 10) The coliform group of bacteria includes all the -------------------- bacilli a) aerobic b) anaerobic c) aerobic, non-sporulating d) aerobic, Gram-negative, non-sporulating 11) What will be the plate count of good quality water? a) 10 per ml b) 50 per ml c) 100 per ml d) 1000 per ml 12) Which of the following features contains the largest amount of phosphorus in the phosphorus cycle? a) The atmosphere b) Rocks and deep oceans sediment c) Ocean water d) Fertilizers and detergents 13) Which of the following features of the carbon cycle is associated with carbon fixation? a) geologic reserves of fossil fuels b) the atmosphere c) ocean water d) plants and other photosynthesizing organisms e)   14) What process causes water molecules to spend a relatively short amount of time in organisms? a) Transpiration b) Infiltration c) Submimation d) Precipitation 15) Which stage of the nitrogen cycle do the arrows in the image represent? a) Nitrogen fixation, in which nitrogen gas is converted into ammonia. b) Denitrification, in which nitrogen gas is released into the atmosphere. c) Nitrification, in which ammonia is converted into nitrate ions. d) Ammonification, in which organic nitrogen is converted into ammonia or ammonium. 16) Which of the following is a definition of a biogeochemical cycle? a) The movement of elements through organisms and the environment b) The movement of elements in organisms' bodies only c) The way that new elements are created on earth. d) The way that elements are lost on earth 17) Which of the following is not a biogeochemical cycle? a) Nitrogen cycle b) Water cycle c) Oxygen cycle d) Carbon cycle 18) What is the process by which atmospheric nitrogen is converted into a form that plants can use? a) Denitrification b) Ammonification c) Nitrification d) Nitrogen fixation 19) Which biogeochemical cycle is essential for the formation of proteins and nucleic acids in living organisms? a) Nitrogen cycle b) Water cycle c) Phosphorus cycle d) Carbon cycle 20) Which biogeochemical cycle is primarily influenced by the combustion of fossil fuels and deforestation? a) Nitrogen cycle b) Water cycle c) Phosphorus cycle d) Carbon cycle

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