Lab Reports



Diffusion and Osmosis through Dialysis Tubing

Purpose/Problem

            The purpose of these experiments is to investigate the influence of solute concentration on osmosis and diffusion.

Background Information

            The membrane of the cell is semipermeable; it must allow some products through such as waste, and materials for the cells.  However, it must also contain all of the enzymes, DNA, and other materials necessary for cell function.  In this lab, the focus will be on passive transport through the semipermeable membrane, or the dialysis tubing.  This has been made semi permeable through the addition of microscopic holes in the sides of the tubing.

Hypothesis: Activity A

1.      If the solution outside the bag tests positive for glucose, then glucose diffused out of the dialysis bag and through the permeable membrane.
2.      If the iodine diffuses into the bag, then it will turn black/blue.
3.      If the starch diffuses out of the bag, the solution will turn black/blue.

Hypothesis: Activity B

1.  If the bag is heavier after the experiment, then the water was transferred in by osmosis.

Materials: Activity A

Dialysis tubing, plastic cup, glucose/starch solution, distilled water, iodine-potassium iodide solution, dropping pipet, glucose test strips, funnel

Materials: Activity B

Dialysis tubing, plastic cups, distilled water, funnel, sucrose solutions, paper towels, balance

Procedures: Activity A

1.       Pour 160-170 mL of distilled water into a plastic cup.  Add approx. 4mL of IKI solution to the water and mix well.  Record solution color.  Dip a glucose strip into the solution and record results.
2.      Dip a fresh glucose test strip into the glucose/starch solution.  Record results.
3.      Obtain a piece of dialysis tubing that has been soaked in water. Close one end by knotting it.
4.      Using a small funnel, pour 15mL of glucose starch solution in the dialysis bag.  Expel the air.  Tie off open end of bag, leaving enough room to allow for expansion.  Record color.  Immerse the dialysis in solution, making sure it is completely covered.
5.      Wait 30 minutes.
6.      Remove bag from cup, and cut a slit to insert the glucose test strip.  Record results.

Procedures: Activity B

1.       Pour 160-170mL of distilled water into a plastic cup.  Label it with the sucrose concentration.
2.      Form a bag with the dialysis tubing by knotting off one end of it. 
3.      Using a small funnel, pour 15mL of sucrose solution into the dialysis bag. Expel the air. Tie off the open end, leaving space for expansion.
4.      Dry the bag and determine the mass.  Record result.
5.      Immerse the bag in the water.  Make sure it is completely covered in water.  Wait 30 minutes.
6.       Remove the bag and dry it on towels.  Mass the bag and record results.  Determine change in mass and record.

Results: Activity A

            In the activity measuring the diffusion through the semipermeable membrane, the results correlated with most of our expectations.  The IKI solution was an orange brown color in the beginning, and ended the same, indicating that starch did not diffuse through the dialysis tubing.  The glucose starch solution inside the bag started out clear and turned black/blue, indicating that the iodine diffused into the bag.  Our initial glucose results tested positive for the glucose/starch solution, and negative for the distilled water.  Our final glucose results were positive for both the water and the solution, indicating that the glucose diffused out of the bag. 

Results: Activity B

In activity B, the experiment tested the change in mass when solutions of different concentrations of sucrose were submerged in distilled water.  The results show that the higher the concentration, the more of a change in mass there was.  For the 0.0M concentration, there was no change.  For the 0.2M concentration, there was a 25.3% change in mass.  For the 0.4M concentration, there was a 46.1% change in mass.  For the 0.6M concentration, there was a 53.76% change in mass.  For the 0.8M concentration, there was a 64.36% change in mass.

Conclusion: Activity A

            Most of the above results for activity A correlated with the hypotheses and predictions.  However, the one result that was not seen was the solution outside of the cup turning a black color.  This indicates that the starch did not diffuse out of the bag.  This was unexpected, but it allows us to draw conclusions about the size of the molecules.  We can determine that the starch molecule is too large to fit through the microscopic holes in the membrane, and this explains the results that we found here. 
            The one substance that was not accounted for here was water.  In order to measure the water transfer, we could collect data about the mass of the bag before and after the experiment.  This would mean that we had then accounted for all of the molecules in this experiment.

Conclusion: Activity B

            This experiment tested the travel of water into and out of the dialysis bag in relation to the concentration of sucrose in the water in the bag.  The results were consistent with what we expected to see, so we can assume that all of the variables were controlled other than the variable we were testing: water.  Our results do indeed support the hypothesis that the water would transfer in by osmosis.  The higher the concentration of sucrose in the water in the bag, the higher the percent change of mass is.  This shows that the more concentrated the sucrose is, the more water is needed to dilute it, and the higher the change in mass.

Presence of Staphylococcus epidermidis, Streptococcus epidermidis and Escherichia coli in casual catch morning urine samples and casual catch afternoon samples.

Purpose:

The purpose of this lab is to discover the bacterial found on urogenital surfaces, as well as how bacteria can enter the urinary tract and cause infections.  This lab taught how to prepare a proper bacterial culture as in a diagnostic laboratory. This lab was also intended to draw conclusions on the sterility of morning urine and afternoon urine.

Background:

A urinary tract infection is a bacterial infection.  It is common among all people, but more so in women.  A urinary tract infection is caused by bacteria from the urogenital area entering the urinary tract.  They are diagnosed by performing a bacterial culture and looking for abnormalities in species and levels.  They are treated with antibiotics, but can also be treated naturally with cranberry juice.  The lab deals specifically with the bacteria species E. coli and S. epidermidisE. coli is a common fecal bacterium that is being tested for in conjunction with urinary tract infections, and S. epidermidis is a common skin bacterium.  S. epidermidis is catalase-positive, so this lab will apply hydrogen peroxide to the bacterium to ensure that it is not Streptococcus.  This lab is also testing for bacteria that are gram positive or negative by manipulating the agar chosen for growing the samples.  Gram positive bacteria will not grow on the dyed agar, and gram negative bacteria will only grow on the dyed agar because of the specific dietary requirements.

Hypotheses:

1.      If E. coli is present in the urine sample then green bacteria will grow on the EMB culture plate.
2.      If S. epidermidis or Streptococcus are present in the urine sample then the bacteria will grow on the phenylethanol culture plate.
3.      If S. epidermidis is present in the urine sample, then the hydrogen peroxide will react with the bacteria and break down to water and gaseous oxygen.
4.      If morning urine is less sterile than afternoon urine, then the morning urine sample cultures will contain more species of bacteria than afternoon samples.

Materials:

Escherichia coli, Staphylococcus epidermidis, EMB agar, Phenylethanol agar, autoclave disposal bag, sterile petri dishes, 3% hydrogen peroxide, sterile applicator sticks, sterile specimen containers, antiseptic pads, 70% ethanol, cotton balls.
Methods:
1.  Disinfect work surfaces and wash hands.
2.  Set out one petri dish of EMB agar and one dish of phenylethanol agar.
3.  Have one person from each group supply a casual catch urine sample. Be sure that the container does not touch clothing or body.  The sample can be refrigerated until ready to be used, but it should be taken as close to the laboratory period as possible.
4.  Remove a sterile applicator stick from the package, and bei9ng careful not to touch the tip to any other surfaces, dip it into the urine sample.  Inoculate the surface of the EMB agar, being sure to cover half of the surface.  Be sure to inoculate heavily because the bacteria will be diluted in the urine.  Label the dish.
5.  Using a fresh stick, inoculate the phenylethanol dish with the same urine sample using the same procedure as before.
6.  Incubate both the control and inoculated plates at 37 C for 48 hours.  Invert the plates to prevent moisture from dripping down onto the agar and obscuring the results.
7.  Observe the plates after 48 hours and note the presence and appearance of the EMB and phenylethanol agars.
8.  Test the S. epidermidis colonies on the control phenylethanol plate with one drop of 3% hydrogen peroxide.  Repeat this step with colonies on the urine-inoculated phenylethanol dishes.  Observe whether bubbling occurs where the hydrogen peroxide is in contact with the culture.  Bubbling is a positive reaction for catalase; no bubbling is a negative catalase reaction.  Record results.

Results:

On the EMB culture plate, all samples were negative except for samples 2 and 8.  On the phenylethanol, all samples were positive except for sample 6 (Table 1).  Samples 1,2,3,4,5, and 8 on the phenylethanol culture plate  tested positive for Staph., and samples 2,6, and 7 tested negative.  Sample 2 tested both positive and negative for reaction to hydrogen peroxide.  Samples 1, 3, 4, 5, 6, and 7 had no bacteria on the EMB plates.  Sample 2 had green colonies growing on the EMB, and sample 8 had purple colonies growing.  All samples had white colonies growing on the phenylethanol except for sample 6, which was negative.  The samples were taken from 3 males and 5 females.  All samples were casual catch samples taken in the afternoon except for sample 7, which was a clean catch afternoon sample, and sample 8, which was a casual catch morning sample.  The control plate for E. coli tested positive on the EMB agar with green colonies, and negative on the phenylethanol agar.  The control plate for Staph. tested negative on the EMB agar, and positive on the phenylethanol agar, with white colonies showing. 

Conclusion:

The data suggest that the first hypothesis, which states that if E. coli is present in the urine sample, then bacteria will grow on the EMB agar plate, can be accepted for sample 2, because green colonies were present.  All other samples, reject this hypothesis suggesting no presence of E. coli.  The only urine samples that tested positive for bacterial growth on the EMB plate were samples 2 and 8.  The colonies on sample 8 were purple, not metallic green indicating that the bacteria present was not E. coli.  I conclude that the purple colonies must be a vigorous fermenter in order to produce the purple color seen.  Past this conclusion, it is unclear exactly what bacterium was growing on that plate.  This leads to the conclusion that E. coli can be present in urine, and will grow on the EMB agar plates.  However, it also leads us to the conclusion that bacterial growth on the EMB agar is not a definite proof of E. coli in the urine, because some sample tested positive, but were clearly not E. coli because of their distinct purple color.
The second hypothesis, which states that if S. epidermidis or Streptococcus are present in the urine sample then the bacteria will grow on the phenylethanol culture plate, can be accepted.  The data show that many urine samples tested positive, and were determined to be either S. epidermidis or Streptococcus.  Based on these results, I conclude that when either bacteria is present in the urine sample, it will show up on the phenylethanol agar.
The third hypothesis, which states that if S. epidermidis is present in the urine sample, then the hydrogen peroxide will react with the bacteria and break down to water and gaseous oxygen, is accepted in samples 1,2,3,4,5, and 8.  This suggests that that the samples are populated with S. epidermidis.  Samples 2, 6 and 7 tested negative.  Samples 6 and 7 showed no bacterial growth, so that can be deemed unimportant data in this conclusion.  Sample 2, however, did have colonies growing on it, and the data suggest that bacteria of both types were growing in the urine sample.  Because of the consistency of finding the S. epidermidis bacteria in the urine samples, the conclusion that can be made is that it is a common bacteria to be found in the urogenital area.
The fourth hypothesis, which states that if morning urine is less sterile than afternoon urine, then the morning urine sample cultures will contain more species of bacteria than afternoon samples, can be accepted, but only on a limited basis.  The sample size for this data set was alarmingly small, leading to the conclusion that a larger conclusion cannot be determined from this data.  The data that is shown is also contradictory towards conclusions.  The one morning sample that was taken did have a significantly higher population of bacteria than sample 4 and 5, but was similar in content to sample 2.  The only significant difference in the morning sample was the presence of the purple colonies, but again, it is unknown as to what caused that.  Therefore, on this hypothesis is can be concluded that there was not enough information gathered, and much contradictory results, that result in no conclusion being drawn.

The interactions of Bacteriophage T4, antiserum T4 and E. coli in relation to bacterial infection prevention.

Purpose:

The purpose of this lab is to explore the reaction between bacteriophage T4 and Escherichia coli, and the reactions between the bacteriophage T4 and the homologous antibody.  This lab presents the problem facing modern medicine, namely, how to prevent the antibodies from attacking the bacteriophage before it has destroyed the bacterium.

Background:

The anticoliphage T4 serum used in this lab is produced through the autoimmune response of a goat when the bacteriophage T4 is injected into it.  The blood serum that is collected after this process contains the antibody for bacteriophage T4.  This antibody is capable of attacking free T4 virions.  These antibodies are produced by the B- cell lymphocytes in the goat’s immune system.  These substances that stimulate the immune system to create antibodies are called antigens.  Specifically, an antibody will be produced that is targeted against that specific antigen.  The trigger for the immune system in this situation has a “head” and “tail”, where each end is a different antigen.  Therefore, in the blood serum sample collected, there are two distinct clones of the antibody.  Despite this, studies have shown that only the antibody that attacks the tail of the virus has an effect on the virus infectivity.  These antibodies neutralize unadsorbed virions, but cannot have an effect on a virion that has already attached to a bacterium.  The free floating antibodies produced by the goat’s immune system mirror the workings of the human system as well, so the results of this lab can be used to tackle the ideas and problems presented by the concept of battling bacterial infections with virulent phages.  This is becoming increasingly relevant in today’s world, because there are increasingly more antibiotic-resistant bacterial infections coming into existence.  A problem yet to be solved is the elimination of the bacteriophages by the antibodies before they have performed their job of eliminating the bacteria.   The removal of the phage by the body’s natural processes does not happen instantaneously, but rather proceeds at a measurable rate.   This is the process being addressed in this lab.

Question:

Might a virulent phage be administered to destroy a particular bacterial infection?

Materials:

Antiserum and coliphage T4 set, 18 tubes dilation and culture broth, 6 tubes soft agar, 6 base-layer agar plates, 21 pipets, 1 mL, marking pen, 5 procedure flowsheets.


Results:

On each plate, the measurements were determined subjectively, by estimating the percent coverage of both phage and E. coli on each culture plate.  This lab was measuring the concentrations of E. coli and bacteriophage T4 on soft agar plates.  The first plate was P-5, meaning that it consisted of phage at a dilution of 10-5.  The results on this agar show E. coli at a concentration of 5% on the plate, and the bacteriophage at a concentration of 95% (Table 1).  This plate presented with a dense film of bacteriophage colonies with sparse scatted milky white E. coli colonies.  The P-6 plate, or phage at a dilution of 10-6, showed 5% E. coli and 70% bacteriophage.   This plate had sparsely scattered milky white E. coli colonies, and densely scattered tiny white bacteriophage colonies.  The 2A/P-5 plate consisted of phage at a 10-5 dilution allowed to interact with the antibody for 2 minutes.  The results show 30% E. coli and 30% bacteriophage, an equal ratio.  This plate held medium sized milky white E. coli colonies, and scattered tiny white phage colonies.  The 4A/P-5 plate consisted of phage at 10-5 dilution and the phage was allowed to interact with the antibody for 4 minutes.  The results show 25% E. coli concentration and a 15% bacteriophage concentration.   The plate held small milky white scattered E. coli colonies, and scattered tiny white bacteriophage colonies.  The 8A/P-5 consisted of phage at 10-5 dilution allowed to interact with the antibody for 8 minutes.  The plate showed a 20% E. coli concentration and a 5% bacteriophage concentration.  The plate held several large white E. coli colonies and scattered tiny white bacteriophage colonies.  The 8A/P-5X plate consisted of phage at a 10-5 dilution allowed to interact with the antibodies for 8 minutes.  This plate showed no signs of life.
Table 1:
Plate Name
E. coli
Bacteriophage
Description
P-5
5%
95%
filmy layer, scattered small E. coli colonies
P-6
5%
70%
small white milky colonies, tons of tiny white dots
2A/P-5
30%
30%
medium white milky colonies, scattered lots of white dots
4A/P-5
25%
15%
small white milky colonies, densely scattered white dots
8A/P-5
20%
5%
Several large white milky colonies, sparsely scattered white dots
8A/P-5X
0%
0%
devoid of all life on the plate









Figure 1:

Conclusion:

The results of this lab can be applied to the question of bacterial infection treatment through bacteriophages.  The effects of the different factors in this lab could lead to more ideas on how to oppress the natural antibody response in human systems.  Our results on the P-5 and P-6 plates showed varying levels of phage growth, which was clearly due to the dilution of the phage added to that plate.  There were no antibodies to inhibit the growth on these plates, so therefore we see an explosion of phage growth, and a very slight presence of e. coli.  The explosive growth seemed to be less on the plate labeled P-6, which correlates because this is a higher dilution of the phage.  On plate 2A/P-5, there appeared to be a dramatic decrease in amount of phage, and almost equal parts phage and e. coli.  This makes sense, because this plate allowed interaction between the antibodies and the phage for 2 minutes.  A lesser amount of phage would be expected here, due to the fact that it is being incapacitated by the antibody.  On plate 4A/P-5, there is recorded a drop in phage on the plate, most likely due to the fact that this plate allowed interaction between the phage and the antibody for 4 minutes instead of 2.  On plate 8A/P-5, there was a drop in numbers of phage colonies, again likely due to the fact that the interaction time between the antibody and the phage was increased to 8 minutes.  Here, it would be safe to conclude that the more time the bacteriophage is exposed to the antibodies, the less survives on the plate.  Plate 8A/P-5X showed no signs of life, which could be predicted, given the fact that this plate contains no e. coli, and the phage was allowed to interact for 8 minutes with the antibodies.  The combination of being attacked, and having no host cells to reside in clearly resulted in complete inability for the phage to take hold.   Out of all of this, it can be concluded that the phage does increasingly worse the more time it is exposed to an antibody, and when it has no host cells, it stands not a chance.  One result that was found that has difficulty being described is the decrease in the numbers of e. coli colonies as the numbers of phage decreased.  The expected result would be that as the number of phages preying on it decreased, the number of e. coli colonies seen would increase, and flourish in the absence of their predator.  This leaves the unanswered question, what is causing the decline in E. coli colonies?  It is possible that if this could be identified, it could lead to yet another treatment option for these kinds of bacterial infections.  Given that some of the possible concerns of bacterial therapy may include difficulty containing the virus, this data suggests that the phage cannot survive without cells to invade, and so could be contained.  One of the questions still to be answered here is how the body’s natural immunological response could be repressed so that the phage could do its job, because clearly the phage does not function nearly as well where it is necessary for it to be attacked as well as attack.  Is there a possibility for a phage that is not recognized by the body as an invader, which can seek out and destroy these bacterial invaders?  This would be a huge advance in modern medicine, if this form of infection management could be achieved.
However, the conclusions drawn in this lab are not necessarily to be trusted, because the sample size here was atrociously small.  Because of technical difficulties during this lab, the number of plates where the results were uncontaminated was much smaller than expected.   The nature of this lab means that if one step in the series was disrupted or performed incorrectly, all of the results would need to be scrapped.  Also, the number of labs performed independently would need to be increased, so that all results were not dependent on the prior person’s accuracy.  Therefore, for the conclusions made here to be trusted, the sample size would need to increase significantly. 


Allele Shuffling of Single Gene Traits in Drosophila
Introduction
The purpose of the experiment conducted was to determine if the shuffling of alleles of single gene traits is indeed random.  The fruit fly, or Drosophila, is an ideal choice for the experiment because of the fast turn-over, or reproductive, rate, require little space, and are easy to feed and handle.  They also only have four pairs of chromosomes, making it easy to identify and observe genetic shuffles.  They have been used for many genetic studies, meaning that there is a wealth of information, as well as many genetically pure strains for additional research.  In the experiment conducted with the Drosophila, if the p-value is greater than 5%, then allele shuffling can be said to be random.
Materials


Sorting brushes, sorting cards, fly morgue, microscope, wild-type flies, mutant A- Se, mutant B- Vg, mutant C- W-, petri dishes, culture vials, potatoes, foam plug, fly nap kit


Methods
Warning: Don’t Inhale fly nap.  Also, the fruit flies may not be native to your area, so do not release them!
1.      Anesthetize all flies in separate vials. 
2.     Examine each type of fly; be sure to note eye color and wing shape for each type.
3.     Make sure you are able to differentiate between the males and females; practice on the flies you have out.
4.     Put the flies in the morgue.
5.     Examine the previously created homozygous crosses and score the F1 generation.
6.     Set up your F1 cross and the culture vial.
7.     Put excess F1 flies in the morgue.
8.     Wait for the results of the F1 cross to be born, and remove the F1 adults to the morgue.
9.     Once the F2 generation has hatched, score them.
10.  Put scored flies in morgue.
Results and Analysis
For cross 1(Sese X Sese), there were 871 red-eyed and 326 sepia-eyed flies counted, with a total of 1197.  In order to discover the number of each type of fly there would be expected from this number, multiply the total found by the decimal forms of the numbers expected.  Sample Equation: 1997*.75=897.75.  The expected numbers were 897.75 and 299.25, respectively.
Equation for finding Chi-squared:
In order to determine whether the numbers fall between reasonable limits, you perform the chi-square equation.  Sample Equation:X2=(871-897.75)2/897.75=0.7971.  This value is then compared to a chart of values, and depending on your degrees of freedom (=options-1) you determine the p-value.  If it is less than the 5% bracket, you can consider it to be significantly off.  The total Chi-square value was 3.19.  For cross 2 (VgvgSese X VgvgSese) there were 197 vestigial winged red eyed flies, 231 vestigial winged sepia eyed flies, 708 normal winged red eyed flies, and 240 normal winged sepia eyed flies.  Some of these numbers deviated significantly from the expected numbers; we expected 258, 86, 774, and 258 respectively.  The total chi-square value for this cross was 265.78.  For cross 3 (W+w- X W+w-) there were observed 228 white eyed males, 184 white eyed females, 240 wild eyed males, and 214 wild eyed females. The expected number for each category was 216.5.  The total chi-square value for this cross was 8.07.
The purpose of this experiment was to determine if the allele shuffling of single gene traits in Drosophila is indeed random.  The hypothesis was that the shuffling of the single gene traits is indeed random.  Had the hypothesis been confirmed, we would see that the chi-square values would all correlate with a p-value greater than 5%.  Cross 1 reinforces and supports the hypotheses.  However, not all other data correlated with the hypothesis.  There were several numbers that contradicted the hypothesis, specifically the values for crosses two and three (VgvgSese X VgvgSese and W+w- X W+w-).  The values for vestigial winged red-eyed flies had a chi value of 14.42, which is much higher than it should be, and this shows that something is amiss.  The values for vestigial winged sepia-eyed flies were also off, and the chi square value was 244.48.  This is very far off of what it should be, and this show that there was something severely amiss in this cross.  There are several options for what could have caused this.  It is possible that the room was not kept at an even temperature, and this could have affected the results of the cross.  The most plausible possibility, however, is that we had a mislabeled vial, or people who counted inaccurately, for whatever reason.  Both numbers that were off were ones that had vestigial wings.  This leads me to believe that the problem was in the misidentification of sepia and red eyed vestigial winged flies.  The fact that there were so many people doing crosses could be helpful in terms of more numbers making more accurate data, except for the fact that the numbers are not easily tracked back to the original counter.  This means that there are not repercussions for people doing a lazy job, or even genuinely being unable to correctly identify the flies.  This dilutes the accuracy of our experiment, and basically negates the results.  However, the huge number of mislabeled flies (approx. 119) suggests that there was something bigger going on.  In order to confirm the hypothesis for this dihybrid cross, I would suggest that the experiment be run again, and this time have a large number of flies being bred by one person, to see if the results are again off.  The other option is to run each cross through the ratios again, but using individual data instead of that from over forty people.  The anomalies can then be detected, and a more accurate picture can be formed.  The results gained from this experiment are not ones that are watertight; therefore to achieve a more accurate result, the experiment should be run again.  Conclusions about the accuracy of the hypothesis cannot be determined from this data, due to the uncertainty surrounding the results.

Ss X Ss
Phenotype Observed Expected Chi-square value p-Value Significant (Y/N)
Red-eyed 871 897.75 0.7971 >5% N
Sepia-eyed 326 299.25 2.3911 >5% N
Total 1197 1197 3.1882 >5% N
VvSs X VvSs
Phenotype observed expected Chi-square Value p-Value Significant(Y/N)
Vestigial red 197 258 14.4224 <5% Y
vestigial sepia 231 86 244.4767 <5% Y
Normal Red 708 774 5.6279 >5% N
Normal Sepia 240 258 1.2558 >5% N
Total 1376 1376 265.7828 <5% Y
Ww X Ww
Phenotype Observed Expected Chi-square Value p-Value Significant (Y/N)
White-Eyed Males 228 216.5 0.6109 >5% N
White-Eyed Females 184 216.5 4.8788 >5% N
Wild-Eyed Males 240 216.5 2.5508 >5% N
Wild-Eyed Females 214 216.5 0.0289 >5% N
Total 866 866 8.0694 <5% Y