Exam 2 will be on Wednesday, March 27, 2019 .

1. Exam 2 will be on Wednesday, March 27, 2019. Place: If your last name starts with A – Pe: please take exam in room 112 Gregory If your last name starts with Ph – Z: please take exam in room 213 Gregory Covers chapters: 5, 6, 5, 7, 5, 9 &10 and 5 Review Session: 7:00 – 8:20 pm, Monday, March 25 Place: Room 124 Burrill Hall

2. Recombinant DNA TechnologyWhat is a restriction enzyme? • a protein that binds to a specific DNA sequence, the protein catalyzes the hydrolysis of specific phosphodiester bonds at that site resulting in the double-stranded cutting of the DNA molecule • a protein that binds to DNA at a site called a promoter, the protein then catalyzes the polymerization ribonucleotides to form of a strand of RNA that is complimentary to one of the DNA strands • a technique that allows one to artificially produce thousands of copies of a specific region of DNA from a single template molecule if you have a set of short DNA molecules called “primers” that bind to the upstream and downstream boundaries of the sequence of interest • a protein the binds to double-stranded DNA structure at a site where there is a break in one of the backbone chains of phosphodiester bonds, the protein then catalyzes the formation of a phosphodiester bond that seals up the break in the nucleotide chain

3. Recombinant DNA Technology What is a restriction enzyme? • a protein that binds to a specific DNA sequence, the protein catalyzes the hydrolysis of specific phosphodiester bonds at that site resulting in the double-stranded cutting of the DNA molecule • a protein that binds to DNA at a site called a promoter, the protein then catalyzes the polymerization ribonucleotides to form of a strand of RNA that is complimentary to one of the DNA strands RNA polymerase • a technique that allows one to artificially produce thousands of copies of a specific region of DNA from a single template molecule if you have a set of short DNA molecules called “primers” that bind to the upstream and downstream boundaries of the sequence of interestPCR polymerase chain reaction • a protein the binds to double-stranded DNA structure at a site where there is a break in one of the backbone chains of phosphodiester bonds, the protein then catalyzes the formation of a phosphodiester bond that seals up the break in the nucleotide chain • DNA ligase

4. MCB 100 Introductory Microbiology 2019 Chapter 9 from Microbiology by Bauman Physical and Chemical Antimicrobial Agents Treatments & Substances That Kill or Inhibit Microbes physical agents: heat, cold, radiation, desiccation (drying) chemicals: detergents, solvents, oxidizing agents, metals

5. What is the difference between bacteriocidal and bacteriostatic? A bacteriocidal agent is a physical or chemical treatment that will kill bacteria, whereas a bacteriostatic agent will prevent the growth of bacteria, but will not kill them.

6. Why would anybody want to use a bacteriostatic agent instead of a bacteriocidal agent? A bacteriostatic agent or treatment may provide adequate protection of the product from bacteria without destroying the product. Conditions needed to kill bacterial endospores are so harsh they may damage the product that you want to protect from the bacteria. For example:Incineration kills bacteria but it isn't a very good way to preserve meat. Adding salt or spices or drying meat is bacteriostatic rather than bacteriocidal, but it will stop or slow bacterial growth on the meat. This slows spoilage without destroying the meat. Refrigeration is bacteriostatic.

7. Factors That Affect Efficiency of a Bacteriocidal Treatment What is the species of microorganism that you are most worried about? Maybe you don't have to kill every species of bacteria in a sample in order to achieve the desired effect. Some species of bacteria are easier to kill than others.

8. Factors That Affect Efficiency of a Bacteriocidal Treatment What is the material that needs to be protected from microorganisms? A process that sterilizes a metal instrument may be too harsh to use on food or plastic. A procedure that works for preservation of one type of food may be inappropriate for another.

9. Factors That Affect Efficiency of a Bacteriocidal Treatment Biological factors that affect the efficiency of a sterilization procedure include the age of the cells that you want to kill and the size of the population of bacteria that you want to get rid of.

10. Factors That Can Affect the Efficiency of a Bacteriocidal Treatment Environmental factors that affect the efficiency of a sterilization or preservation procedure include: the storage temperature of the product, the pH, the water activity (osmotic pressure), and the presence of organic matter.

11. Which of the following factors can affect the killing efficiency of a microbicidal agent? A. the species of microorganism that must be killed B. the temperature of treatment C. the pH of the medium D. the microbial load (a lot of bacteria vs. a few) E. all of the above

12. Which of the following factors can affect the killing efficiency of a microbicidal agent? A. the species of microorganism that must be killed B. the temperature of treatment C. the pH of the medium D. the microbial load (a lot of bacteria vs. a few)E. all of the above

13. What is an “autoclave”? A. a refrigerator B. a device that kills microorganisms with dry heat C. a device that kills microorganisms by freeze- drying them D. a device for killing microorganisms by exposing articles to hot steam under pressure E. a very small car that bacteria drive to work when they must commute more than 1 mm

14. What is an “autoclave”? A. a refrigerator B. a device that kills microorganisms with dry heat C. a device that kills microorganisms by freeze- drying them D. a device for killing microorganisms by exposing articles to hot steam under pressure E. a very small car that bacteria drive to work when they must commute more than 1 mm

15. Killing Microbes With Heat Antimicrobial treatments kill by damaging a vital cellular structure or by inhibiting a metabolic reaction. Heat kills bacteria by denaturing proteins and nucleic acids. Heat also disrupts the cell membrane structure. Moist heat kills bacteria faster than dry heat because water has a higher heat capacity than air.

17. Killing Microorganisms With Heat: Steam, Boiling Water and Dry Heat Compressed steam is hotter than boiling waterso you can use it to heat the sample to a higher temperature. How does dry heat sterilization differ from moist heat sterilization? What are some applications of dry heat sterilization? Moist heat kills cells by denaturing proteins, nucleic acids and the cell membrane causing the cytoplasm to turn into a coagulated mass. Dry heat removes water from the cell and causes oxidation of organic matter, basically the bacteria slowly burn until they turn into little pieces of charcoal. Dry heat is used to sterilize metal or glass instruments that can take the heat. Usually scientists and doctors like their tools to be dry, because it prevents rust and makes it easier to hold them. Sterilizing ovens are hot, usually 200 – 300oC. 250oC is 482oF, cakes are baked at 350 oF. Paper can catch on fire in a sterilizing oven. Items like paper or cloth are usually sterilized in an autoclave using moist heat and then placed in a drying oven, which is about 130 – 150oC.

18. Comparison of Times and Temperatures to Achieve Sterilization with Moist and Dry Heat Time to Sterilize Moist Heat 121oC 15 min. 134oC 3 min. Dry Heat 121oC 600 min. 140oC 180 min. 170oC 60 min. A. Average Thermal Death Times of Vegetative Bacteria vs. Endospores MicrobeTemperatureTypeTime (min.) Non-spore forming pathogenic bacteria 58oC moist heat 28 vegetative stage of spore-forming bacteria 58oC moist heat 19 Clostridium botulinum endospores 120oC moist heat 10 Clostridium botulinum endospores 120oC dry heat 120 B.

19. Pasteurization: Disinfection of Beverages Using a Minimal Amount of Heat Beverages such as milk, fruit juices, beer and wine are easily contaminated with microorganisms during collection and processing. These contaminating microorganisms can cause spoilage of the product or may be human pathogens. Pasteurization is the application of heat to a liquid to kill potential agents of infection and spoilage without destroying the product’s taste or nutritional value. Milk is typically heated to 72oC for 15 seconds in a special heat exchanger (flash method), or 65oC for 30 minutes (batch method). This amount of heat is sufficient to kill most viruses and vegetative stages of bacteria and fungi. Pasteurization of milk is designed to kill non-spore forming pathogens, especially: - Mycobacterium bovis and Mycobacterium tuberculosis (TB), - Coxiella burnetii (Q-fever), - Salmonella typhi (typhoid fever), - Campylobacter jejuni (gastroenteritis) - Listeria monocytogenes (listeriosis).

20. Which one of the following statements about pasteurization is false? Pasteurization is an antimicrobial procedure that: _____________ A. kills most viruses and pathogenic bacteria that don’t form spores. B. helps prevent the spread of Tuberculosis, Listeriosis and Salmonellosis. C. is designed to kill Clostridium botulinum spores. D. is used to decontaminate beverages such as milk, fruit juices, wine and beer. E. was invented by Louis Pasteur.

21. Which one of the following statements about pasteurization is FALSE? Pasteurization is an antimicrobial procedure that: _____________ A. kills most viruses and pathogenic bacteria that don’t form spores. B. helps prevent the spread of Tuberculosis, Listeriosis and Salmonellosis. C. is designed to kill Clostridium botulinum spores. D. is used to decontaminate beverages such as milk, fruit juices, wine and beer. E. was invented by Louis Pasteur.

22. REFRIGERATION (a bacteriostatic treatment) * Refrigeration slows or stops bacterial growth but it does not kill them. * Cold temperatures are generally bacteriostatic rather than bacteriocidal. * Some microorganisms will grow in the refrigerator, but they grow slowly. * Refrigeration prevents the growth of most disease causing bacteria because they are adapted for growth in the human body. * Freezing kills some bacteria by causing the formation of ice crystals that can disrupt the cell membrane, but most bacteria can survive freezing if they are put into a 15% solution of glycerol. A refrigerator,(temperature ~4oC or ~39oF) is a slow incubator. Micrococcus roseus