2. You have been asked to set up a dilution series, and then use spread plates to determine the viable cell count. Why is it necessary to use a dilution series when isolating bacteria from a biological sample using spread plating? [5 MARKS]
It is vital to use a dilution series to reduce the concentration of the original biological sample so it is easier to count the number of isolated colonies which are present on the spread plate. The diluted samples will have a workable number of colonies on the spread plate which can then be used to calculate the number of bacteria which were present in the original undiluted sample.
3. You plate the dilutions onto nutrient agar and chromogenic agar plates. What are the differences between these types
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4. What temperature should the plates be incubated at and why? [2 MARKS]
Both the nutrient and chromogenic plates should be incubated at 37 degrees Celsius because this will mimic the temperature of the birthing pools where the sample is from as well as mimicking the temperature of the human body.
5. You use cUTI plates as the chromogenic media and find that some of the colonies have turned pink in colour. What information does this tell you about the bacteria in the sample, and why did the colony change colour? [2 marks]
This tells me that the bacteria in the sample contains coliforms such as Escherichia coli (E.coli). The colonies changed colour as the enzymes produced by the bacterial cells reacted with the red galactosidase in the agar medium, this reaction causes the colonies to turn pink making them easily
Organic modifiers are used to change the retention time of different analytes. Organic modifiers lower mobile phase polarity. By increasing the amount of water lead to the repulsion of hydrophobic analytes out of the mobile phase. The hydrophobic analytes are pushed onto the stationary phase where they reside for duration up to the partitioning into the mobile phase. When ionic analytes exist in the sample, the addition of ion and buffer to the mobile phase are necessary.
After 5 days the plates were removed from the cold room and the gram-negative test for Colony A on the EMB agar showed pink fisheye colonies which lead to the conclusion that the gram-negative organism within Unknown #21 was Enterobacter aerogenes. Had the pigmentation been metallic green, the organism would have been identified as Escherichia coli, and had there been no pigmentation at all a Triple Sugar Iron agar (TSI) test among other tests would have been
Neutral red acts as a pH indicator, it remains colorless when the pH is above 6.8 and becomes red when the pH falls lower than 6.8 (3). The gram-negative coliform type bacteria would turn this medium red, while bacteria that do not ferment lactose will not incur a color change. The MSA plate is also considered a selective and differential medium. MacConkey is commonly used to differentiate between different species in the Enterobacteriaceae family. MSA is considered selective because it contains 7.5% NaCl and only bacteria that can survive the high osmotic pressure due to the sodium chloride will be able to grow on this plate.
Interpretation NA plate: The NA plate had growth of both organism even though it was difficult to differentiate between the colonies on this
On the first negative control plate, there should have been no growth on the plate with agar and ampicillin and regular E. coli cells. On the negative control plate with just agar and E. coli cells there should have been growth but the colonies would not
coli bacteria new traits. The pGLO plasmid that is being transformed into these cells contains genes that can give colonies of bacteria the ability of antibiotic resistance and a green fluorescent glow. Four different models were prepared and plated on multiple agar plate. After the bacteria was grown for three days in an incubator at 37°C; observations were made and recorded (Table 1). All of the plates were looked at for the amount of colonies grown, if growth was present, and if the colonies gained the ability to glow green.
The initial test conducted after being given unknown bacteria number 5 was a Three-Step gram stain. This test was conducted utilizing aseptic technique. I first aseptically prepared a smear using unknown bacteria number 5 and heat fixed the smear. I then flooded the smear with
Each plate serves as a first step to identify the unknowns. The TSA (tryptic soy agar) can be used to do a gram stain, which differentiates gram-negatives from gram-positives, based on the structural make up of the cell wall (Carson, 2015). The blood agar plate is used to test for hemolytic activity, which is useful for distinguishing gram-positives. A MacConkey plate is selective by inhibiting the growth of gram-positives and differential due to the fermentation of lactose by certain gram-negative species. In the
The unknown bacteria was then tested on multiple selective and differential media. Growth was present on the MacConkey Agar and the colonies were the same color as the plate, which told me my bacteria was gram negative and did not ferment lactose. There was no growth on the Mannitol Salt Agar, and this told me the unknown was not salt tolerant and did not
The second ½ of the organism was used for gram staining. The gram stain method was performed on the unknown organism per lab manual page 42 and two gram stain reactions were identified. Organism B was gram positive cocci in grape like clusters. Because organism B was positive I could eliminate Escherichia coli, Enterobacter aerogenes and Proteus vulgaris because these bacteria would be rod shapes. Organism A was gram negative pink rod shaped and because of gram positive morphology I could eliminate Staphylococcus aureus, Streptococcus lactis and Bacillus subtilis.
The streaking technique used was a modified streaking for isolation with a heavy quadrant one. The result revealed that bacteria is alpha, with an incomplete breakdown of the medium with a susceptibility of 17mm from the bacitracin gamma hemolysis. That is why the organism represented by the bar graph was in low numbers because it was incomplete. The other test was DNase agar, it is an enzyme test used to identify if the organism has the enzyme DNA. The streaking technique is a single straight line down the middle of the plate.
Experiment 2: Distillation and Purification of Liquids Angela Kaiser 100125701 ELL 308 September 19th, 2015 Introduction and Experimental: The purpose of this experiment was to determine the ratio of dichloromethane (DCM) to cyclohexane in a DCM/cyclohexane solution by carrying out a fractional distillation. The temperature and volume of distillate were measured periodically to determine the volume both components in the solution. The experiment was performed as written in “Experiment 2: Distillation and Purification of Liquids” from the Chemistry 2050 Lab Manual for Organic Chemistry Part 1, Fall 2015. Results and Observations:
The concentration of the stock solution 2.0x 10-4M as per label information in the lab. However, the calculated volume using the experimental data is 1.5 x 10-4M.There is 25% difference between these concentration caluclated from zero time intercept. The significant difference in the concentration drop happened by many factors. First,the rate ionization is depend the pH because pKa determines the equlibrium between p-nitrophenol and its depronated form p-nitrophenolate. Although,the pH is maintained by buffer at 7,not all of the p-nitrophenol produced by the chymotrpsin catalysis is not its depronated form.
From the Unknown tube professor Cooper gave me, I scratched a little on the slant surface with the sterilized inoculating loop. Then I place it on a clean prepared slide which already had a slight drop of water. The two substances are mixed together in the middle of the slide and let dry completely. One extra step of “heat fix” is necessary to adhere everything to the surface of the slide. To start gram staining, I slightly pour crystal-violet all over the slide and let it sit for 30 seconds before wash it off with water.
Research question: Does green tea inhibit oral bacteria? Aim: To determine whether green tea inhibits oral bacteria Hypothesis: The strongest green tea solution will inhibit the greatest amount of growth in oral bacteria Independent variable: