DISCUSSION

Assuming that serial dilution was carried out in a laboratory experiment in 6 tubes with 9 ml of saline in each tube and 0.1ml of the stock solution was used for initial dilution, pour plate method of inoculation was performed after the dilution process using 1ml of the culture from the samples from the test tubes. It was found out that on the 6th Petri dish after incubation, there was a total of 16 individual colonies counted. Compute the total number of microorganisms present in tube one, assuming that there was no human error in the transferring proces.

a. Explain whether or not any of the methods in fi gure 2.9 could beused to determine the total number of cells present in a patient’s specimen.b. After performing the streak plate method on a bacterial specimen, theculture was incubated for 48 hours at 37°C. Upon viewing the plate, therewas heavy growth (with no isolated colonies) in the fi rst quadrant, but nogrowth was apparent in the remaining quadrants. Please discuss errors in the procedure that could have produced this result.

A bacterial culture that has been pretreated with penicillin to inhibit its peptidoglycan synthesis is split and put into solutions of various concentrations. The same is done with a control culture with no prior penicillin exposure. Which condition is likely to demonstrate the biggest difference in outcomes between the control culture and the experimental culture? Placing the cultures into an isotonic solution Placing the cultures into a hypotonic solution Placing the cultures into a hypertonic solution The control and experimental cultures should show you the same results in every condition

Below is a diagram of four different antibiotics (numbered 1-4) that are being tested in a petri dish inoculated with bacteria. After a sufficient incubation period, bacterial growth occurred except in the zones of inhibition (shown with dotted lines in the diagram) around the antibiotics. Based on the results shown here, would it be reasonable to conclude that the most effective antibiotic in this example would be an effective antibiotic against any bacterium? Why or why not?

The following results were obtained from a disk diffusion test for microbial susceptibility to antibiotics. Staphylococcus aureus was the test organism. Use these data to answer questions. The following results were obtained using the Kirby-Bauer method to assess microbial susceptibility to antibiotics. Staphylococcus aureus was the experimental organism. Use the data below to answer the questions. antibiotics Zone of Inhibition TO 3mm В. 7mm C Omm 10mm The most effective antibiotic was: Select one: O TO B. can't tell O O O O O

A pure bacterial culture of unknown concentration was diluted to determine the concentration of viable bacteria in the original culture. Serial dilutions were performed as 1. diagrammed below. Each dilution tube contained 400 ul of diluent and 100 ul was transferred into each tube. TSA plates were inoculated with 100 µul from the last three dilution tubes. a. What is the dilution between each tube shown in the diagram below? Express your answer as a ratio. b. What is the total dilution of tube number 5? Express your answer as a ratio. c. What is the concentration of viable bacteria in the original culture? Express your answer using scientific notation and the units CFU/ml. d. What is the concentration of viable bacteria in tube number 2? Express your answer using the units CFU/ml. e. If you inoculated a TSA plate with 250 µl from tube number 5, how many colonies would you expect to see after the plate was incubated? 1 2 3 5 423 80 13 Number of colonies

In Exercise 2-1:Ubiquity of Microorganism, we used two unopened plates as controls: one was incubated at 25° C and one was incubated at 37° C. What information do you get from these controls to give you confidence in your results? How does growth on an unopened plate affect the reliability of the other plates that were inoculated in this experiment?

A pure bacterial culture of unknown concentration was diluted to determine the concentration of viable bacteria in the original culture. Serial dilutions were performed as 2. diagrammed below. A volume of 500 µl was transferred into each tube. TSA plates were inoculated with 100 µl from the last three dilution tubes. a. If the dilution between each tube is 102, what is the volume of diluent in each of the 5 dilution tubes? Provide the volume using ml as the units. b. What is the total dilution of tube number 4? Express the total dilution using scientific notation. c. What is the concentration of viable bacteria in the original culture? Express the concentration using scientific notation and CFU/ml as the units. d. If you inoculated a TSA plate with 1.0 ml from dilution tube 4, how many colonies would you expect to form on the plate after incubation? e. If the original culture had a volume of 50ml, what was the total number of viable bacteria in the 50 ml of the original culture? 1 2 3…

For a laboratory exercise of antibiotic susceptibility test in a disk-diffusion method. With reference to the table below, determine the antibiotic susceptibilities of different antibiotics against E.coli and S.aureus.

The total number of cells in a culture is counted using the trypan blue exclusion assay and is found to be 6.8 x 106 cells/ml. Each well in a 6 well plate requires 2 x 105 cells. How should the solution be diluted so that 1ml can be added to each well?

SEPARATION OF COMPONENTS BY CENTRIFUGATION Consider the following subcellular components and their corresponding sedimentation rates. Table 3. Sedimentation rates of four subcellular components for isolation. CENTRIFUGAL FORCE (xg) SUBCELLULAR COMPONENT CDCP 14896 AJRA 967 AGC 382 JCKSP 2378 Two centrifuge machines are available in your laboratory. Centrifuge A has a rotor diameter of 14 cm and a maximum speed of 3500 rpm while centrifuge B has a rotor diameter of 18 cm and a maximum speed of 14500 rpm. Construct a separation scheme of the four subcellular components considering the following parameters: The four components are separated into pellet/supernatant I and pellet/supernatant II. Only two centrifugation steps are performed; specify the centrifugal speeds (in rpm) per step. Show relevant calculations. Both centrifuge machines must be used in the procedure. Components of each fraction are indicated.

A culture of E. coli is diluted as follows:(1) 65mL are added to 435mL of water.(2) 10uL from (1) are then added to 9.99mL of water.(3) A 10-3 dilution is made from tube # (2).(4) 100uL from (3) are plated for a pour plate and incubated. There were 34 colonies counted on one quarter of the plate following incubation. a) What was the overall dilution?b) How many cfu/mL were present in the original culture?c) How many milliliters of water is needed to make a 10-3 dilution using 1000 uL from the original culture?

In a fed-batch culture operating with intermittent addition of lactose solution, values ofthe following parameters are given at time t = 2, when the system is at a quasi-steady state. 1.Determine the initial volume of the culture 2. Determine the concentration of growth-limiting substrate and the total amount ofbiomass in the vessel at a quasi-steady state. 3. At which scenario of bioprocessing, a fed-batch system is recommended to be applied?

Your animal cell culture laboratory suddenly suffered from a bacterial contamination. Several components like vitamins, yeast hydrolysate, and fetal calf serum are temperature sensitive and must be filtered through a bacteriological filter to add to the autoclaved animal cell culture media. After careful considerations, you found that there are no issues with the autoclaving, but there is something wrong with the filter sterilization process, and changing new batches of filter did not remove the bacterial contamination. Which of the following rationale best describes the probable cause? Group of answer choices A. The media is probably contaminated with E. coli,  which passed through the 0.2-micron bacteriological filter. B. The media is probably contaminated with Mycoplasma, due to the lack of cell walls they are the only bacteria that can pass through the 0.2-micron bacteriological filter.   C. All of the other answer choices could be correct D. The media is probably…

You spread 0.1 mL volume of a 10^(-6) dilution onto a nutrient agar plate. After 24 hours of incubation at 37°C, there were 280 colonies of bacteria on the plate. A.) What is the original concentration (OCD) of bacteria in the stock sample this dilution came from?  B.) Using the OCD value from part A, determine the number of colonies that would be expected to grow on a plate that is inoculated with 0.1 mL volume of 10^(-8) dilution from this same stock of bacteria.  Show your work for both.

You spread 0.1 mL volume of a 10^(-6) dilution onto a nutrient agar plate. After 24 hours of incubation at 37°C, there were 280 colonies of bacteria on the plate. A.) What is the original concentration (OCD) of bacteria in the stock sample this dilution came from?  B.) Using the OCD value from part A, determine the number of colonies that would be expected to grow on a plate that is inoculated with 0.1 mL volume of 10^(-8) dilution from this same stock of bacteria.

Which of the following is a reason to run simultaneous tests on known positive and negative controls when identifying an unknown microbe using biochemical tests? The controls maintain the differential qualities of the test medium The controls can show if there was contamination of the tubes with another species The controls will ensure that the unknown microbe multiplies on the medium The controls can show if there was a recent mutation in your unknown microbe

Below is shown a growth curve for an E. coli culture. As indicated, the culture was incubated in the absence of a carbon source for 2 hours until Glucose and Lactose were added; Glucose was used up after 5 hours, and Lactose was used up after 8 hours. During the time-course, you take four samples, labeled A-D, after 1, 3, 7 and 9 hours, respectively, as indicated under the graph. Assuming there is cAMP present at t=0, for each sample identify whether CAP and/or the Lac Repressor would be bound to the DNA, and explain why.

Below is shown a growth curve for an E. coli culture. As indicated, the culture was incubated in the absence of a carbon source for 2 hours until Glucose and Lactose were added; Glucose was used up after 5 hours, and Lactose was used up after 8 hours. During the time-course, you take four samples, labeled A-D, after 1, 3, 7 and 9 hours, respectively, as indicated under the graph. Assuming there is cAMP present at t=0, for each sample identify whether CAP and/or the Lac Repressor would be bound to the DNA, and explain why.

How would you produce a 10^-1 dilution if a 3 mL bacterial sample using the entire 3 mL volume?  suppose your professor handed you a test tube with 2.0 mL of an E. coli broth culture in it and told you to make a 10^-1 dilution of the entire culture. Explain how you would do this. Show your calculations.

The number of bacteria in culture increases rapidly. The table below gives the number of bacteria a few times (in hours) after the moment when. (a) Find the average rate of change for the number of bacteria from 0 hours to 3.1 hours. (b) Find the average rate of change for the number of bacteria from 6.2 hours to 15.5 hours.

Blood agar is often used to observe changes in the appear-ance of the agar around the colonies growing on this medium.This medium could then be called:(a) Selective(b) Designated(c) Differential(d) Defined(e) Exact

You are tasked to observe the motility of an UNKNOWN Bacteria isolated from a mixed culture, which technique/s is BEST to perform? How shall the procedure be carried out? Explain.

Per the USDA, whole, unpasteurized fresh eggs can contain no more than 50,000 CFU/mL bacteria in a standard plate count. You are curious if the fresh eggs that you buy from your neighbor are considered safe to consume so you use your eScience Microbiology kit to test these eggs using direct plate count after serial dilution. After you complete the experiment, you obtain 74 countable colonies from the 10-2 dilution plate. The inoculum volume you plated was 0.1 mL.   How many bacteria are present in 1 mL of the egg you sampled?   Are these eggs considered safe to consume per USDA standards?

The colony forming units (CFU)/ml in sauerkraut brine are given for different types of bacteria except for leuconostoc (shaded column). To obtain the Leuconostoc counts for different days, 40 microlitre of sauerkraut brine was 10-fold diluted and the CFU was determined by plating different dilutions on agar plates. For Day 0 56 CFU were counted in 10-1 dilution, Day 1 81 CFU were counted in 10-3 dilution, Day 2 86 CFU were counted in 10-3 dilution Day 5 78 CFU were counted in 10-5 dilution     Calculate the CFU/ml of leuconostoc in the brine for the 4 different days. Show your calculation

A phagehunter performs a full plate titer using standard techniques (100 ul of each dilution added to 250 ul of Gordonia terrae cells) of a lysate obtained from an optimum webbed plate experiment. The phagehunter counts 72 plaques on the 10-7 dilution plate. Which of the following scenarios is the best choice for the phagehunter to do next? a.) The phagehunter has not achieved a high enough titer lysate to move forward with characterization experiments, so they should adopt a phage from direct isolation. b.) The phagehunter has not achieved a high enough titer lysate to move forward with characterization experiments, so they should go back to the pick-a-plaque experiment. c.) The phagehunter has achieved a high enough titer lysate to move forward with characterization experiments. d.) The phagehunter has not achieved a high enough titer lysate to move forward with characterization experiments, so they should try to make more optimum webbed plates.

You have several different media onto which you inoculated eight strains of yeast (A-H). The media include a rich medium, an unsupplemented minimal medium, and minimal media each supplemented with one vitamin. Of the yeast strains, one is a prototroph and seven are auxotrophs for a vitamin. After overnight incubation, the following results were observed (tan patches represent growth): D plate 1 (A) B DE F GH plate 5 plate 4 plate 6 Which plate contains an unsupplemented minimal medium? [Select] Which plate contains a rich medium? [Select] plate 2 Which strain is a prototroph? [Select] Strain E is an auxotroph for niacin. Which plate reveals this specific auxotrophy? [ Select] plate 3 plate 7 One strain is an auxotroph for both choline and pantothenic acid. Which one is this most likely to be? [Select]

Вackground In order to determine whether a newly synthesized chemical might be a useful food preservative, the chemical was tested for its ability to inhibit bacterial growth. Control. 500 ml of cottage cheese was inoculated with 2 ml of a 24-hr culture of Pseudomonas aeruginosa and incubated at 25°C. Five hours after inoculation, a standard plate count showed there were 200 bacterial cells/ml in the cottage cheese. After 11 hours, 1600 cells/ml. After 21 hours, 50,000 cells/ml. After 27 hours, 400,000 cells/ml. Experiment. 500 ml of cottage cheese containing the preservative was inoculated with 2 ml of a 24-hr culture of P. aeruginosa. After 6 hours of incubation at 25°C, a standard plate count was performed. There were 700 bacterial cells/ml in the cottage cheese. After 14 hours, 11,000 cells/ml. After 20 hours, 90,000 cells/ml. After 28 hours, 1, 400, 000 cells/ml. Use the data and the semi-log graph paper to plot growth curves for the control and the experiment. Remember to label…