one or your lab partners has followed the rrecommended procedure of running Gram-positive and Gram negative control organisms on her gram stain of an unknown species. Her choices of conrols were Escherichia Coli and Vacillus subtilis. She tries several times and each time concludes she is decolorizing too long because both controls have pink cells (one more than the other) What might you suggest and why?
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one or your lab partners has followed the rrecommended procedure of running Gram-positive and Gram negative control organisms on her
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- One of your lab partners has followed the recommended procedure of running Gram-positive and Gram-negative control organisms on her Gram stain of an unknown species. Her choices of controls were Escherichia coli and Bacillus subtilis. She tries several times and each time concludes she is decolorizing too long because both controls have pink cells (one more than the other). What might you suggest she try and why?Out of the three gram-positive bacteria (Micrococcus luteus, Staphylococcus aureus, and Staphylococcus epidermidis). Which of the following test(s) will help me identify the unknown gram-positive bacteria? Gram Stain Wet Mount (motility testing) Endospore Staining Acid Fast Staining Differential & Selective Media (MacConkey, PEA, EMB, MSA Agar, Blood Agar, etc.) Oxidative-Fermentative Test Carbohydrate Fermentation MR-VP Testing Indole Production Citrate Utilization Triple Sugar Iron Testing Catalase TestA mixed culture is known to contain Gram negative bacilli and Gram positive cocci. You perform a Gram stain of this mixed culture as a control while simultaneously Gram stainin an unknown organism on the same slide (the same procedure you used in lab). The results, observed under the 100x objective lens, are described below: Results: Control side: purple bacilli and purple cocci Unknown side: purple bacilli Using all the information given above, discuss the results of your unknown organism. Shoul you be confident in this result? Answer question A if you are confident, answer question B if you are not confident. a. If you are confident in your results, why? Explain how the staining reagents produced the described results. b. If you are not confident, do you think an error was made in the Gram staining procedure? If so, describe the error and explain how it impacted your results.
- In the image attached is a unknown bacteria lab. The gram stain result and growth result is already given to us and is shown. What other tests (1-2 examples) could we use to follow up this test. Explain why we should use those tests with justification.You are working through the Gram Staining procedure on a mixed culture of S. aureus (G+) and E. coli (G-) (gram + & gram -) organisms respectively. If you accidentally use too much alcohol / acetone during the procedure, which of the following will likely happen? E. coliE. coli will appear to be Gram + will appear to be Gram +E. coli will appear to be Gram + S. aureus will appear to be Gram - Both organisms will appear colorless Both organisms will appear purple None of the answers are correctYou have identified two colony types A and B on the streak plate. Now briefly describe (in 3-4 sentences) the process of how you identified the cellular morphology/arrangement of each isolate. Again, assume you have all the necessary equipment and materials at your disposal. Be concise and thorough, not verbose; e.g., refer to the Gram stain, but describing the details of each step is not necessary.
- The acid-fast bacterium, Mycobacterium smegmatis, is relatively safe to be used by students in performing the acid-fast stain technique because of its thin cell wall. However, if this organism is used for Gram-stain, it can also take the Gram stain reaction. Why is this so?Using your fingers, you are asked to aseptically touch the surface of a sterile agar plate. Illustrate the possible result from this step if your fingers are (a) unwashed – touched various things prior to placing on agar surface, and (b) washed with soap or disinfected with 70% alcohol. Describe the relative abundance of microbial growth observed on the plates. List and draw the possible characteristics of an isolated bacterial colony that can be observed based on type of (a) margin, (b) elevation, (c) texture, and (d) optical property.Kousei works at a company that produces sweetened condensed milk. If one or more samples exceed 104 bacterial CFU/mL (or CFU/g) the entire lot produced will be rejected. Kousei's boss, Kaori, wanted to know if the lot passed the FDA guidelines. The following bacterial counts were obtained after serial dilution and pour plating of the samples: Type of Dilutions plated 10-4 10-³ 10'5 Colony Plate 1 Plate 2 Plate 1 Plate 2 Plate 3 Plate 1 Plate 2 Plate 3 Plate 3 244 Bacteria 288 251 99 81 75 24 21 15 Based on the bacterial counts obtained, will the lot be rejected? Yes, because the computed CFU/mL is 2.5 x 10^7 OYes, because the computed CFU/mL is 3.0 x 10^6 No, because the computed CFU/mL is 3.0 x 10^3 No, because the computed CFU/mL is 2.5 x 10^3 OYes, because the computed CFU/mL is 3.8 x 10^5 O No, because the computed CFU/mL is 3.0 x 10^3 O Information is lacking so CFU/mL cannot be computed
- MacConkey agar is often used to differentiate E. coli from other Gram-negative rods. The recipe for MacConkey agar is given in the table. Suppose you plated a mixed culture of Escherichia coli, Bacillus subtilis, and Streptococcus pyogenes onto a MacConkey agar plate. Which species would grow, and how would they appear? Why would the others NOT grow?1. Sally Monella found 344 bacterial colonies on one of her plates. She had prepared this plate after a serial dilution of a culture of Yersinia pestis. She had pipetted 1 ml sample of diluted Yersinia pestis from a tube with the overall dilution factor of 106 into a plate and covered it with agar. She used this plate to calculate the concentration in cells/ml of a bacterial culture. a) How many organisms were in the original culture? b) Were her results valid? Why or why not?A lab technician is working with a bacterium in pure culture (in 5 ml of liquid media in a test tube). The bacterium is a mesophile that can infect humans. Which of the following is NOT true (with regards to temperature conditions for this bacterial culture)? Lowering the temperature to -10 deg C for at least an hour will likely kill all the bacteria. Placing the tube at 37 deg C will likely facilitate rapid growth of the bacteria. Raising the temperature to 90 deg C for at least an hour will likely kill all the bacteria. Placing the tube at 4 deg C will likely slow or halt growth of the bacteria.