A specific heat treatment used on a particular bacterial suspension has a DRT of 10 seconds, how much time would be required to achieve a 5 log reduction in numbers of bacteria?
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A specific heat treatment used on a particular bacterial suspension has a DRT of 10 seconds, how much time would be required to achieve a 5 log reduction in numbers of bacteria?
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- Why should agar media be completely dissolved before they are dispensed in tubes and plates? What are the bases for pegging the temperature at 1210C for 15-30 minutes during moist heat sterilization and 1800C for two (2) hours using dry heat sterilization? Can you sterilize culture media using dry heat sterilization? Why is that so? You will notice in the videos shown, the cotton plug is not used. What is role of cotton plug in media prep, sterilization and culture of microorganisms? Instead of using cotton plug, plastic screw-cap is used, can you substitute this for the former? Is it technically acceptable in microbiology?A microbiologist has isolated a new strain of bacteria, and is trying to characterize aspects of its growth. Three flasks of the same media have different amounts of NaCl added. Other growth conditions are identical, and the flasks inoculated at the same time. At regular intervals over a 3 hour period, culture samples are taken and turbidity is measured. Here are the absorbance values over time in a table and graphed. Absorbance (OD600) Time (min) 20% NaCl 3% NaCl 0% NaCl 0 0.05 0.05 0.05 30 0.06 0.05 0.05 60 0.075 0.06 0.05 90 0.11 0.07 0.049 120 0.25 0.1 0.048 150 0.5 0.105 0.055 180 0.7 0.11 0.055 210 0.99 0.15 0.06 240 1.22 0.18 0.055 270 1.35 0.19 0.06 300 1.5 0.2 0.06 330 1.6 0.25 0.062 360 1.7 0.3 0.06 Based on these data, which of the following can be determined about this bacterium? It is psychrophilic. It…Assume an inoculum with a cell density of 108 cells per mL. The entire generation time takes 30 minutes. How many hours would it take to grow a culture to 108/mL if you started with a 10–2 dilution? helpful formula: g (generation time) = 0.301 (time)/ log x – log xo
- use these OD numbers to plot growth curve for E. coli K12- and estimate generation time for this culture. Table 1. Absorbance (O.D.600) measured for growing culture of E. coli K12 (time course) Incubation time O.D.600 Incubation time O.D.600 O min 3 hrs 3 hrs 30 min 4 hrs 4 hrs 30 min 5 hrs 5 hrs 30 min 0.11 1.75 30 min 0.20 1.94 1 hr 1 hr 30 min 2 hrs 2 hrs 30 min 0.27 2.24 0.51 2.48 2.31 2.19 0.65 1.30Given the scenario, compute for the total volume of the culture media solution (milliliter or liter) and dehydrated media (grams). Scenario: The students of a Microbiology class were tasked to transfer or subculture a pure culture of Escherichia coli bacterium in five 7 mL nutrient broth and five petri dishes of nutrient agar with 20 mL capacity each. Based on the instruction bottles for nutrient broth and nutrient agar, preparation of the culture media is as follows. Nutrient broth: 8 g/liter Nutrient agar: 28 g/liter Formula: C1V1 = C2V2 *Concentration *Volume Computation: What are the answers to the following. Weight in grams of nutrient broth: _________ Distilled water in mL for nutrient broth: __________ Weight in grams of nutrient agar __________ Distilled water in mL for nutrient agar: ____________If 5% w/v concentration of a bactericide of dilution coefficient of 3 takes 25 minutes to effect killing, what will be the time of kill when it is diluted 8 times A sanitizer with dilution coefficient of 0.5 takes 3 minutes to effect killing. If it takes 18 minutes to kill when it is diluted 5times, what is the initial concentration? An unknown concentration of ‘LD’ disinfectant killed 106 viable cells of Sporotrichum schenkii within a certain time. When the concentration was increased 2-fold the extinction time decreased a 103-fold. Determine the concentration exponent of this disinfectant
- What would the final concentration of a bacteria culture be if 2.7 x 106 cells/ml were diluted 8.2 x 10-2? What would the initial concentration of a bacteria culture be if the final concentration was 3.7 x 102 cells/ml and the total dilution was 4.6 x 10-4?(b) A Food material containing Bacillus stearothermophilus PS1518 as an indicator organism ts subjected to heat sterilization at 121 C. Calculate the time required to reduce the organism to one tenth of the original number. Fo value for the organism is 4 minutes and the decimal reduction time , D, at 116°C is 40 minutes. Assume operation is at constant temperature of 121°C. HINT Fo = -To 10 dt Where Fo = equivalent exposure time at 121°C of the actual exposure time at a variable temperature To = the reference temperature =121 C, z=10 = number ofC necessary for10fold increase in Fstarting with four bacterial cells per milliliter in a rich nutrient medium, with a 1-hour lag phase and a 30-minute generation time, how many cells will there be in 1 ml of this culture after 10 hours?
- If the sterile glycerol stock is 40%, what will be the volume of the bacterial culture in a nutrient broth that must be added to have a final concentration necessary for a glycerol stock culture? the final volume in the microfuge tube must be 1ml. Compute. Answers should be in a microliter.The thermal death point is best described as:(a) The highest temperature that will support growth of amicrobial culture(b) The length of time required for killing 100% of mi-crobes in a 24-hour culture that is heated to 100°C(c) The temperature at which a previously growing 24-hourculture will begin to die(d) The temperature at which 100% of the microbes in a24-hour culture will be killed in 10 minutesYou have found that the D-value (decimal reduction value) of an antimicrobial agent to be 4 minutes when the agent was exposed to a bacterial culture having an initial total viable cel1 count of 10° CFU/mL. After 4 minutes upon addition of the antimicrobial agent, what would have been the total viable count of the culture in this experiment? A) O 10° CFU/mL B) O 10$ CFU/mL C) O 10° CFU/mL D) O 10' CFU/mL