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unit 5 microbio
| Question | Answer |
|---|---|
| What enables the copied chromosomes to separate during binary fission? | the chromosomes are attached to diffrent parts of cell membrane, which elongates and thus separates the chromosomes |
| How long does it take for the daughter cells from one round of replication to replicate themselves? | no time is required - they are ready to divide immediately after DNA replication and separation of the daughter cells is complete if conditions are right. |
| Put the following steps of bacterial replication in the correct order, starting from a parent cell. | chromosome replication, cell elongation, septum formation, seperation of daughter cells |
| What would happen if the septum did not form during binary fission? | the parent cell would not have two copies of the chromosomes |
| Starting with three cells, how many cells would result from three rounds of replication? | twenty-four |
| Microbial growth is generally described as an increase in cell number rather than the expansion in size of an individual microbial cell. | true |
| Fts proteins are essential for bacterial cell division because they __________. | are responsible for pulling apart the two copies of the chromosomes, are responsible for peptidoglycan synthesis, are responsible for forming the division. |
| The time interval required for the formation of two cells from one is called the | generation time |
| Which of the following is/are transferred to daughter cells during bacterial cell division? | chromosomes, protiens, and all other cellular constituents |
| If a bacterial culture contains 1 cell at time zero, 4 cells after 1 hour, and 16 cells after 2 hours, then all EXCEPT which of the following are true? | the growth rate is increasing with each generation |
| The lag phase does NOT occur if an exponentially growing culture is transferred into a nutrient rich medium with the same components and growth conditions as the previous medium. | true |
| Which of the following statements is FALSE? | in the lag phase, cell death exceeds cell division |
| Cell density in a chemostat is controlled by | the concentration of the limiting nutrient |
| A selective medium is used to suppress the growth of certain bacteria in order to facilitate the growth of other bacteria. | true |
| Microbial contamination is prevented by the | use of aseptic technique |
| Selective medium differs from differential medium because | selective medium permits growth of a particular microbial type while differential medium is used to distinguish between types of organisms |
| A medium containing known substances in precise amounts is known as a ________ media. | defines |
| Serial dilutions are generally made | to reach a suitable dilution while minimizing error. based on powers of 10, although other serial dilution factors are possible. when the appropriate viable count is unknown. |
| Direct microscopic counting of cells is an accurate method for estimating the number of viable cells in a sample. | false |
| Turbidity measurements are commonly utilized for monitoring | planktonic cultures |
| Refrigeration controls microbial growth in food as a result of irreversible cell damage caused by low temperature. | false |
| Organisms able to live in environments with high sugar concentrations are | osmophiles |
| When water activity is low, an organism must | increase its internal solute concentration. |
| Superoxide dismutase and catalase work together to convert superoxide into | water and oxygen |
| Which of the following forms of oxygen is/are generally toxic to living organisms? | Superoxide, hydrogen peroxide, and hydroxyl radicals are all toxic. |
| field test be a direct or indirect method? Why? If your field test comes back as being above the safe threshold, one example of a specific method you could use in the lab accurate count of the bacterial load? Would this be a direct or indirect method? | field test- indirect, doesnt accurately count bacteria. turbitidy and absence/presence over threshold- standard plate count. direct method |
| Why are some forms of oxygen toxic? How do obligate aerobes tolerate these oxygen forms if it can kill obligate anaerobes? | |
| You have just inoculated a sterile broth tube with a culture of Serratia marcescens. Describe the four phases of growth it will go through over the next 3 weeks if you leave it out at room temperature. | lag, log, stationary, and death |
| How does a viable cell count differ from a total cell count? Does this matter? Provide an example of a quantitative method that provides a viable cell count. | Viable cell count - living tissues Total cell count - living and non-living tissues Dying with trypan blue dye which excludes dead cells, serial dilution and plate count Important for testing |
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