Bio 420 Lecture 2

Both human cells and bacterial cells divide by mitosis. TRUE or FALSE

False Explanation: Bacteria divide by binary fission and human cells divide by mitosis. The processes are similar in the fact that both involve the division of one cell into two genetically identical cells.

Cell division is triggered exclusively when cells attain a threshold mass. TRUE/FALSE

FALSE X: Cell division is triggered exclusively when cells attain a threshold mass and length.

DNA helicase is responsible for adding nucleotides to the growing end of the DNA. TRUE/FALSE

FALSE X: DNA helicase is responsible for unwinding the DNA double helix so replication can begin. DNA polymerase is responsible for adding the nucleotides to the chain.

Measures to prevent prion contamination of healthcare settings have been in place for the past several decades and fully control the risk True or False

False

Regarding use of heat to control microbial growth, dry heat at lower temperatures is as effective as moist heat at the same temperature. True or False

False

Sterilization is the destruction of all living microbes from a surface by physical or chemical means. True or False

False

Cells cannot begin a new round of replication until they have completely finished dividing. true or False

False X: A new round of cell division can occur before the cells complete division.

Chlorine is safely used to disinfect waste liquids, some medical instruments, and various surfaces. It is readily available in liquid household bleach but bleach must be diluted because high concentrations are toxic and corrosive. To obtain an effective concentration of chlorine when using household bleach, a 1:100 dilution is made. This means that ______ mL of bleach is added to ______ mL of water. 0.1/100 99/1.0 1.0/100 99/0.1 1.0/99 0.1/99

1.0 / 99

Consider a culture of E. coli growing in exponential phase with a generation time of 20 minutes. Beginning with 2 x 106 cells per ml, how long will it take the culture to reach a density of about 3.2 x 107 cells per ml? 120 min 80 miin 100 min 60 min 40 min

80 min X: We know the population of cells will double every 20 minutes. One way to solve this problem is with the formula Nt = N0 x 2n, where Nt is the number of cells at a given time (in minutes), N0 is the initial number of cells, and n is the number of generations. In this question, Nt = 3.2 x 107 cells/ml, N0 = 2 x 106 cells/ml, and we need to solve for the number of generations. This gives us 3.2 x 107 cells/ml = 2 x 106 cells/ml x 2n, or 2n = (3.2 x 107 / 2 x 106), or 2n = 16, or n = 4 generations. Since the generation time is 20 minutes, after 4 generations, 80 minutes will have elapsed.

Match each type of bacteria with the appropriate incubation setup. Capnophile Aerobe Microaerophile Obligate anaerobe Benchtop Candle jar Gastight container with chemical pack that reduces oxygen to 5-15% Gastight container with chemical pack that reduces oxygen to ~0%

Aerobe - Benchtop Capnophile - Candle jar Microaerophiloe - Gastight container with chemical pack that reduces oxygen to 5-15% Obligate anaerobe - Gastight container with chemical pack that reduces oxygen to ~0%

Following the Exxon Valdez oil spill, beaches in Prince William Sound were treated with nitrogen compounds in order to enhance the bioremediation of the oil. What does this tell you about the ecosystem of these beaches? a) Microorganisms are unable to grow on the abundant hydrocarbons found in oil. b) With the arrival of large quantities of hydrocarbons, nitrogen was a limiting nutrient for microbial growth. c) Nitrogen was used to react with the hydrocarbons of oil in order to enhance its degradation. d) With the arrival of large quantities of nitrogen, carbon was a limiting nutrient for microbial growth. e) With the arrival of large quantities of hydrocarbons, phosphorous was a limiting nutrient for microbial growth.

Answer is B X: Although oil-degrading microbes are found in the environment that can help bioremediate such spills, the enormous imbalance of carbon relative to other essential nutrients can limit microbial growth. In this case, nitrogen was especially limiting relative to carbon. Following research to demonstrate the effectiveness of fertilizing with nitrogen, over a hundred thousand pounds of nitrogen fertilizer was applied over the next few years to accelerate the microbial degradation of the oil contamination.

Shown are results from membrane filtration of a water sample. Choose the statement that best describes this process. a) Only the microbes found in the collection bottle are grown on the agar plate b) Only the microbes too large to make it through the filter are grown on the agar plate c) Only the microbes that are small enough to pass through the filter are grown non the agar plate

Answer is: B

Boiling is not a reliable method for sterilization because: a) water boils at different temperatures at different altitudes b) it releases toxic substances from water c) it does not destroy heat-resistant endospores d) it causes the release of toxins from endospores

Answer is: C

Choose which of the following best describe the difference between a disinfectant and an antiseptic. a) Disinfectants are chemicals that reduce the number of pathogenic microbes on an inanimate surface or object. Antiseptics are chemicals used to delay the spoilage of food or other perishable materials by slowing the growth of microorganisms. b) Disinfectants are chemicals that completely destroys all microbes on a product. Antiseptics are chemicals that reduce the number of microbes on a product. c) Disinfectants are antimicrobial chemicals used on inanimate surfaces or objects to remove most of the pathogenic microorganisms. Antiseptics are antimicrobial chemicals that can be used on skin or tissues to achieve the same result. d) Disinfectants and antiseptics are both types of chemicals used to remove microbes from any kind of surface. They are used interchangeably. e) Disinfectants are chemicals that reduce the number of microbes to meet accepted health standards. Antiseptics are chemicals that completely eliminate of all microbes/viruses from a surface.

Answer is: C

Select the correct statements about autoclaving. a) Autoclaving involves the use of both temperature and pressure b) Autoclaving was pioneered by Louis Pasteur and is used to preserve food c) Autoclave tape is used to ensure that an object has been effectively sterilized d) Biological indicators such as heat-resistant endospores are used to ensure that an autoclave is working properly e) Autoclaving is consistently effective in sterilizing most objects f) Adding pressure to the autoclave increases the temperature of the steam in it g) The pressure used in autoclaving plays a direct role in killing microbes

Answers are: A, C, D, E, F

You have a culture of bacteria in which cells are dying off at a constant rate. This culture is most likely in ______ phase. stationary log death prolonged decline lag

Death X: During death phase, the total number of viable cells in the population decreases as cells die off at a constant rate. The rate of death is exponential.

Please match the term with its description to test your understanding of microbial control terminology. 1) Sterilization 2) Decontamination 3) Preservation 4) Disinfection Destruction of all microbial life Reduction of most microbial life on inanimate surfaces Mechanical removal of most microbes from living or inanimate surfaces Slows microbial growth but does not reduce the number of existing microbes.

Destruction of all microbial life ~~#1 Reduction of most microbial life on inanimate surfaces ~~ #4 Mechanical removal of most microbes from living or inanimate surfaces ~~#2 Slows microbial growth but does not reduce the number of existing microbes. ~~#3

Production of extracellular polymeric substances (EPS) is necessary for bacteria to form biofilms. communicate with other cells. grow in cold climates such as the Arctic. make endospores. undergo DNA mediated transformation.

Form biofilm X: Bacteria frequently grow in polymer-encased communities called biofilms. These involve the production and release of polysaccharides, DNA, and other hydrophilic polymers, yielding a slimy, mesh-like accumulation of polymers refered to as extracellular polymeric substances, or EPS.

Match the descriptions and antimicrobial agents to the appropriate type of germicide to test your knowledge of alcohols, halogens, phenolic compounds, and quaternary ammonium compounds as germicidal chemicals. Halogens/ Quaternary Ammonium Compounds/ Alcohols/Phenolic Compounds These compounds are ineffective against mycobacteria, naked viruses and Pseudomonas species. Carbolic acid Compound reacts with membranes to destroy many vegetative bacteria and enveloped viruses Solutions can be used as antiseptics or to disinfect instruments and surfaces without leaving a residue. Chlorine, chlorine dioxide, iodine Ethanol or isopropanol Germicidal agent which can leave an antimicrobial residue after use. Aqueous solutions which kill vegetative bacteria and fungi but not bacterial endospores or naked viruses. Common disinfectant which oxidizes proteins and other cell components Cationic detergent which can be safely used on food preparation surfaces

Halogens: -Chlorine, chlorine dioxide, iodine -Common disinfectant which oxidizes proteins and other cell components Quaternary Ammonium Compounds -Cationic detergent which can be safely used on food preparation surfaces -Compound reacts with membranes to destroy many vegetative bacteria and enveloped viruses -These compounds are ineffective against mycobacteria, naked viruses and Pseudomonas species Alcohols - Aqueous solutions which kill vegetative bacteria and fungi but not bacterial endospores or naked viruses. - Solutions can be used as antiseptics or to disinfect instruments and surfaces without leaving a residue. - Ethanol or isopropanol Phenolic Compounds Carbolic acid Germicidal agent which can leave an antimicrobial residue after use.

Identify the phases of a bacterial growth curve. Not all labels are used. Climb phase Lag phase Exponential phase Decline phase Stationary phase Dormancy phase Arithmetic phase Spore phase

Lag phase Exponential phase Stationary phase Decline phase

Match the listed objects and compounds with the appropriate method used to destroy microbes and viruses on/in them. Moist heat/ Dry heat/ Radiation Animal carcasses Heat-sensitive medication Inoculating loop Culture media Medical waste Milk Meat products

Moist heat : Culture media Milk Dry heat: Medical waste Inoculating loop Animal carcasses Radiation: Meat products Heat-sensitive medications

Place the labels into the correct columns for moist heat and dry heat. Moist heat/ Dry heat Used to sterilize surgical instruments Autoclaving Used to prevent food spoilage Pasteurization Used to treat drinking water Burns cell components Less efficient Denatures proteins Used to destroy animal carcasses Bunsen Burner More efficient Used to sterilize microbial media Used to destroy medical wastes Dry heat ovens Boiling Incineration

Moist heat: Pasteurization Denatures proteins More efficient Used to prevent food spoilage Used to sterilize microbial media Used to treat drinking water Used to sterilize surgical instruments Autoclaving Boiling Dry heat: Incineration Burns cell component Less efficient Used to destroy medical wastes Used to destroy animal carcasses Dry heat ovens Bunsen burner

Which enzyme is NOT involved in DNA replication? Ligase Helicase Gyrase DNA polymerase RNA polymerase

RNA polymerase Expl: Helicase, gyrase, DNA polymerase, and ligase are needed for DNA replication to take place.

Cells must ______ their DNA prior to cell division. hydrolyze translate replicate denature transcribe

Replicate

The FtsZ protein is needed to form the ______. ribosome replicated DNA septum mitochondria All of these

Septum Explanation: The FtsZ protein is needed to form the septum between dividing cells.

Match the labels with the observed pattern of growth based upon oxygen requirements. Not all labels are used. Facultative aerobes Facultative anaerobes Microaerophile Obligate anaerobe obligate mesophile Aerotolerant anaerobe Obligate aerobe

Starting from left side: Obligate aerobe Facultative anaerobe Obligate anaerobe Microaerophile Aerotolerant anaerobe

Identify the types of microorganisms based on their optimal growth temperatures. Not all labels are used. Thermophile Psychrotrops Hyperpsychrotrops Anaerobes Mesophile Hyperthermophiles Hypotrophs Psychrophile

Starting with the blue: Psychrophile Psychrotroph Mesophile Thermophile Hyperthermophile

Match the term to its description to test your understanding of the use of moist heat to control microbial growth. Steam under pressure Commercial canning Pasteurization a) Requires use of an autoclave. To sterilize, temperature must reach 121°C for a minimum of 15 minutes. b) Heat applied to beverages to prevent spoilage and kill pathogens. High-temperature-short-time protocols include holding liquids at 72°C for 15 sec. Does not sterilize. c) Uses an autoclave called a retort to destroy the endospores of Clostridium botulinum. It will not destroy the endospores of some thermophiles.

Steam under pressure ~~ a) Pasteurization ~~ b) Commercial canning ~~ c)

Microbes will only grow until the least represented (limiting) nutrient is used up. True or False

True

Environmental factors control microbial growth through their effect on enzyme activity. True or False

True Explanation: Factors such as pH, temperature, and moisture have an effect on bacterial enzymes, which influence bacterial cell division.

Most cultured bacteria tend to multiply by _____. fragmentation binary fusion budding sexual reproduction binary fission

binary fission X: Bacteria cultured in the lab usually multiply by binary fission.

The energy source for contraction of the FtsZ ring during cell division comes from ______. the hydrolysis of ATP the hydrolysis of gyrase the synthesis of GAP the hydrolysis of GTP the synthesis of gyrase

the hydrolysis of GTP Expl: GTP hydrolysis provides the necessary energy for the contraction of the FtsZ ring.