Aseptic Technique and Culture Methods

Aseptic technique is a set of procedures used in a microbiology laboratory to prevent contamination of samples and cultures. It ensures that only the desired microorganisms are introduced into a culture medium, preventing the growth of unwanted organisms and maintaining the integrity of the experiment or analysis.

One common tool used in aseptic technique is the loop or inoculating needle. These are sterilized by heating them until they become red-hot and then allowed to cool before use. The loop or needle is used to transfer microorganisms from one location to another. To do this, the loop or needle is first sterilized by passing it through a flame, then it is used to pick up a small sample of the desired microorganism. The sample can be transferred to a culture medium or used for further analysis.

In addition to loops and needles, there are other methods for inoculating cultures aseptically. These include pipettes, swabs, and spreaders. Pipettes are used to transfer precise volumes of liquid samples, while swabs can be used to collect samples from surfaces or organisms. Spreaders are used to evenly distribute samples over the surface of a culture medium.

When transferring microorganisms from screw top test tubes or petri plates, aseptic technique involves holding the tube or plate upside-down. This minimizes the chance of airborne contaminants falling onto the sample during transfer. The cap of the tube or the lid of the petri plate is partially or completely removed, and the inoculating loop or needle is used to transfer the desired microorganism. The cap or lid is then replaced, and the tube or plate is returned to its upright position.

Quadrant streaking is a common aseptic transfer method used to isolate individual colonies of bacteria on an agar plate. The technique involves using an inoculating loop to streak the sample back and forth across the plate in a pattern that divides the plate into four quadrants. With each streak, the loop is sterilized to prevent contamination between quadrants. This method allows for the isolation of individual colonies for further analysis.

Lawn creation, or spread plating, is another aseptic technique used to evenly distribute a liquid sample over the entire surface of an agar plate. A small amount of the sample is spread across the plate using a sterile spreader or a bent glass rod. This technique produces a dense growth of microorganisms covering the entire plate.

Other common streaking techniques include T-streaking, zig-zag streaking, and double streaking. These methods are used to obtain isolated colonies or to dilute a sample for counting or analysis.

Overall, aseptic technique and procedures in a microbiology laboratory are crucial to maintain the purity of cultures, prevent cross-contamination, and ensure reliable results in experiments and analyses.

Disinfecting Work Spaces

1.       Ensure you have a sufficient amount of 70% ethanol solution ready for disinfection.

a.       If using a spray bottle, ensure it is clean and labeled appropriately for ethanol disinfection.

b.       If using disinfectant wipes, check that they are compatible with ethanol and are within their expiration date.

2.       Put on disposable gloves and, if necessary, a lab coat and safety goggles to protect yourself during the disinfection process.

3.       Before disinfection, remove visible dirt, debris, or spills from the surface by cleaning it with soap and water or an appropriate cleaning agent.

a.       Rinse the surface with water if using a cleaning agent, and ensure it is completely dry before proceeding to disinfection.

4.       Lay dry paper towels on the work surface

a.       Hold the spray bottle about 6-8 inches away from the paper towel and spray the ethanol solution evenly over the paper towel.

b.       Make sure to cover the entire paper towel thoroughly without over-saturating it.

c.        Use the paper towel to wipe off any excess ethanol after the contact time has passed.

5.       Properly dispose of contaminated materials according to laboratory guidelines and biohazard waste disposal procedures.

a.       Remove and discard disposable gloves and wash your hands thoroughly with soap and water after disinfection.

6.       Perform this protocol before and after using a work space

Flaming a Loop or Needle

1.       Ensure that the Bunsen burner is set up on a stable, heat-resistant surface and ignited according to laboratory safety protocols.

2.       Pick up the inoculating loop or needle with one hand, grasping it by the handle, and hold it in a comfortable position.

3.       Position yourself at a safe distance from the Bunsen burner to avoid accidental burns while flaming.

4.       With your other hand, turn on the gas supply to the Bunsen burner and ignite the flame using a striker or a lighter.

5.       Adjust the air vent of the Bunsen burner to create a blue flame with a light blue cone in the center.

6.       Hold the loop or needle with the wire portion facing downwards towards the flame as seen in Figure 1.

7.       Carefully insert the loop or needle into the hottest part of the flame, which is the tip of the blue cone.

8.       Ensure that the entire loop or needle, including the wire and handle, comes into contact with the flame.

9.       Keep the loop or needle in the flame for approximately 5-10 seconds, or until it becomes red-hot.

10.    During flaming, avoid waving the loop or needle around excessively, as this may cause splattering of contaminants.

11.    After the appropriate time, remove the loop or needle from the flame.

12.    Allow the loop or needle to cool for a few seconds by holding it in a non-contaminated area (e.g., sterile bench or a heat-resistant pad).

13.    Before using the loop or needle for any transfer or inoculation, ensure that it has cooled down sufficiently to avoid damaging the cultures or medium.

14.    If you need to flame the loop or needle again, repeat steps 6 to 13.

15.    When you have finished using the loop or needle, turn off the gas supply to the Bunsen burner

Flaming the glass Necks

1.       Ensure that the Bunsen burner is set up on a stable, heat-resistant surface and ignited according to laboratory safety protocols.

a.       Place the test tubes or bottles, along with their lids, in a clean and organized test tube or bottle rack.

2.       Position the test tubes or bottles in the rack, leaving enough space between each one to avoid accidental knocking or tipping during the flaming process.

3.       Pick up the first test tube or bottle you wish to flame and hold it securely by the base with one hand.

a.       With your other hand, hold the lid of the test tube or bottle, ensuring you don't touch the inside of the cap.

4.       Carefully bring the neck of the test tube or bottle close to the flame of the Bunsen burner.

a.       Rotate the test tube or bottle gently and continuously, exposing the entire neck to the flame.

b.       Ensure that the flame comes into contact with all parts of the neck, including the outer and inner surfaces.

5.       Keep the neck of the test tube or bottle in the flame for approximately 5-10 seconds. This duration is sufficient to sterilize the surface.

6.       After flaming the first test tube or bottle, place it back into the rack, ensuring it remains upright.

a.       Move on to the next test tube or bottle in the rack and repeat steps 3 to 5.

7.       After flaming all the test tubes or bottles, visually inspect the necks to ensure they appear clean and sterile.

8.       Let the test tubes or bottles cool down for a few seconds before further handling or capping.

9.       If you need to flame additional test tubes or bottles, repeat steps 3 to 7 as necessary.

10.    Always exercise caution while working with a Bunsen burner to avoid accidental burns or fires.

a.       Make sure to wear appropriate personal protective equipment (PPE), such as lab coats and safety goggles, during the procedure.

Pipette 

1.       Place the pipette pump on a stable and clean surface near your working area as in Figure 2.

a.       Ensure that the pipette pump is properly calibrated and adjusted to the desired volume setting before use.

2.       Select the appropriate pipette tip size for your desired volume. Make sure the tips are compatible with the pipette.

a.       Attach the pipette tip firmly to the end of the pipette. Ensure a secure fit to prevent any leakage during pipetting.

3.       Press the top button or lever on the pipette pump to the first stop to engage the suction.

a.       Immerse the pipette tip into the liquid you want to transfer.

b.       Slowly release the top button or lever to draw the liquid into the pipette tip. The volume should match the pre-set volume on the pipette pump.

4.       With the liquid drawn into the pipette, lift the pipette tip out of the liquid.

a.       Move the pipette tip to the destination container where you want to dispense the liquid.

b.       Position the pipette tip slightly above the liquid surface in the destination container.

c.        Press the top button or lever on the pipette pump to the first stop to begin dispensing the liquid.

d.       To fully dispense the liquid, press the top button or lever down to the second stop, and then release it completely.

5.       After each use, discard the pipette tip into a designated waste container.

a.       To prevent cross-contamination, replace the pipette tip with a new one before transferring different liquids.

6.       Regularly clean the exterior of the pipette and pipette pump with a mild detergent or disinfectant.

a.       If necessary, check the manufacturer's instructions for the specific model to learn about the recommended maintenance and calibration procedures.

7.       Store the pipette and pipette pump in a clean, dust-free area when not in use.

a.       Make sure to store the pipette in an upright position to prevent any liquid from entering the body of the pipette.

Inoculating Loop Techniques

Ensure that the Bunsen burner is set up on a stable, heat-resistant surface and ignited according to laboratory safety protocols.

1.       With your dominant hand to pick up the inoculating loop.

2.       Sterilize the inoculating loop by passing it through the flame of the Bunsen burner until it becomes red-hot. Ensure that the entire loop, including the wire and handle, is exposed to the flame.

3.       Allow the loop to cool while holding the loops’ handle.

4.       Collect a sample of culture from the prepared medium

a.       If collecting from a broth, with your off-dominant hand, pick up the test tube, holding it firmly but gently.

                                                               i.      Gently shake the broth culture to ensure the microorganisms are evenly distributed.

                                                             ii.      Grasp the lid of the test tube with your pinkie finger of the dominant hand.

                                                            iii.      Rotate the test tube between your fingers by rolling it away from you. This motion should be controlled and smooth.

                                                            iv.      As you rotate the test tube, keep your pinkie finger in place to hold the lid as it loosens.

                                                              v.      Once the lid is loosened, carefully remove it from the test tube using your pinkie finger.

                                                            vi.      With the test tube still in your hand flame the neck of the broth culture tube by carefully passing it through the Bunsen burner flame a few times. This helps prevent contaminants from entering the tube during the transfer.

                                                          vii.      Hold the loop at an angle and dip the loop into the broth, ensuring that the loop is completely submerged.

                                                         viii.      Carefully withdraw the loop from the broth, allowing any excess liquid to drain off.

                                                            ix.      Immediately replace the cap on the broth culture tube to prevent contamination.

b.       If collecting from a plate, gently place the plate upside down and pick up only the bottom.

                                                               i.      While the agar is exposed (still upside down), tilt the plate so it’s visible without turning it over. (Do not raise above your head)

                                                             ii.      Use the loop to gently remove one colony from the plate without digging into the agar.

                                                            iii.      Replace the bottom of the plate to the lid.

5.       Transfer the sample to the desired medium.

a.       If transferring to an agar plate

                                                               i.      Remove the lid partially or completely.

                                                             ii.      Gently streak the loop back and forth across the surface of the agar plate or spread the sample over the agar surface, depending on the desired technique (Figure 4).

                                                            iii.      Replace the lid on the agar plate and ensure it is securely closed.

b.       If transferring to a slant

                                                               i.      Put the culture test tube in your hand and pick up a sterile slant test tube.

                                                             ii.      Repeat the same procedure to remove the new test tubes lid.

                                                            iii.      Gently streak the loop back and forth across the surface of the agar slant.

c.        If transferring to a broth

                                                               i.      Put the culture test tube in your hand and pick up a sterile broth test tube.

                                                             ii.      Repeat the same procedure to remove the new test tubes lid.

                                                            iii.      Insert the loop into the new test tubes broth and gently stir a few times to disperse the bacteria.

6.       Sterilize the loop again by passing it through the flame until red-hot for a few seconds to ensure any remaining bacteria on the loop are killed. Then allow the loop to cool.

7.       Properly dispose of any used cultures or contaminated materials according to laboratory guidelines.

Inoculating Needle Techniques

Deep Tubes

1.       Ensure that the Bunsen burner is set up on a stable, heat-resistant surface and ignited according to laboratory safety protocols.

2.       With your dominant hand, pick up the inoculating needle.

3.       Sterilize the inoculating needle by passing it through the flame of the Bunsen burner until it becomes red-hot. Ensure that the entire needle, including the wire and handle, is exposed to the flame.

4.       Allow the needle to cool while holding its handle.

5.       With your off-dominant hand, pick up the stock culture broth tube, holding it firmly but gently.

6.       Gently shake the stock culture broth to ensure the microorganisms are evenly distributed.

7.       Grasp the lid of the stock culture broth tube with your pinkie finger of the dominant hand.

8.       Rotate the stock culture broth tube between your fingers by rolling it away from you. This motion should be controlled and smooth.

9.       As you rotate the stock culture broth tube, keep your pinkie finger in place to hold the lid as it loosens.

10.    Once the lid is loosened, carefully remove it from the stock culture broth tube using your pinkie finger.

11.    Hold the stock culture broth tube in your off-dominant hand while holding the inoculating needle in the other hand.

12.    Flame the neck of the stock culture broth tube by carefully passing it through the Bunsen burner flame a few times. This step helps prevent contaminants from entering the tube during the transfer.

13.    Insert the inoculating needle into the stock culture tube and mix it around for a couple of seconds.

14.    Replace the lid and put down the stock culture broth tube in a safe and designated area, ensuring it remains upright.

15.    Pick up the deep agar tube with your off-dominant hand, holding it firmly but gently.

16.    Repeat the procedure above to remove the cap.

17.    Flame the neck of the deep agar tube by carefully passing it through the Bunsen burner flame a few times.

18.    Carefully insert the inoculating needle into the deep agar tube, pushing the needle through the middle down to the bottom of the media.

19.    Replace the lid on the deep agar tube promptly to prevent contamination.

20.    Sterilize the inoculating needle again by passing it through the flame until it becomes red-hot and then allow it to cool.

21.    Properly dispose of any used cultures or contaminated materials according to laboratory guidelines.

Slant Tubes

1.       Ensure that the Bunsen burner is set up on a stable, heat-resistant surface and ignited according to laboratory safety protocols.

2.       With your dominant hand, pick up the inoculating loop.

3.       Sterilize the inoculating loop by passing it through the flame of the Bunsen burner until it becomes red-hot. Ensure that the entire loop, including the wire, is exposed to the flame.

4.       Allow the loop to cool while holding its handle.

5.       With your off-dominant hand, pick up the stock culture broth tube, holding it firmly but gently.

6.       Gently shake the stock culture broth to ensure the microorganisms are evenly distributed.

7.       Grasp the lid of the stock culture broth tube with your pinkie finger of the dominant hand.

8.       Rotate the stock culture broth tube between your fingers by rolling it away from you. This motion should be controlled and smooth.

9.       As you rotate the stock culture broth tube, keep your pinkie finger in place to hold the lid as it loosens.

10.    Once the lid is loosened, carefully remove it from the stock culture broth tube using your pinkie finger.

11.    Hold the stock culture broth tube in your off-dominant hand while holding the inoculating loop in the other hand.

12.    Flame the neck of the stock culture broth tube by carefully passing it through the Bunsen burner flame a few times. This step helps prevent contaminants from entering the tube during the transfer.

13.    Insert the inoculating loop into the stock culture tube and mix it around for a couple of seconds to ensure the inoculum is well dispersed.

14.    Replace the lid on the stock culture broth tube and put it down in a safe and designated area, ensuring it remains upright.

15.    Pick up the agar slant tube with your off-dominant hand, holding it firmly but gently.

16.    Repeat the procedure above to remove the cap from the deep agar slant tube.

17.    Flame the neck of the agar slant tube by carefully passing it through the Bunsen burner flame a few times.

18.    Gently streak the loop back and forth along the slanted surface of the agar, covering a portion of the slant, from bottom to top.

19.    Replace the lid on the deep agar slant tube promptly to prevent contamination.

20.    Sterilize the inoculating loop again by passing it through the flame until it becomes red-hot and then allow it to cool.

21.    Properly dispose of any used cultures or contaminated materials according to laboratory guidelines.

Swab Collection

1.       Label the agar plate and the broth tube appropriately to avoid confusion during the transfer process.

2.       Using a Swab on an Agar Plate

a.       Open the sterile cotton swab packaging, being cautious not to touch the cotton tip, see Figure 6.

b.       Hold the cotton swab by the handle and gently rub the cotton tip against the area you wish to sample (e.g., a surface with visible microbial growth).

c.        In the case of a liquid sample, dip the cotton swab into the liquid and let it absorb the sample.

d.       With the collected sample on the cotton tip, carefully streak it onto the surface of the sterile agar plate.

e.       To streak, start from one edge of the plate and drag the swab across the agar surface without lifting it. Then, streak the swab in a back-and-forth motion across the next section, overlapping with the previous streak. Repeat this process for the desired number of streaks.

f.         After streaking, close the agar plate securely and place the swab back into the wrapper it came in.

g.       Incubate it at the appropriate temperature for the specific microbial strain being tested.

3.       Using a Swab in a Broth Culture

a.       Open the sterile cotton swab packaging, being cautious not to touch the cotton tip.

b.       Hold the cotton swab by the handle and gently rub the cotton tip against the area you wish to sample (e.g., a surface with visible microbial growth).

c.        In the case of a liquid sample, dip the cotton swab into the liquid and let it absorb the sample.

d.       With the collected sample on the cotton tip, carefully insert it into the sterile agar broth.

e.       Gently rotate the cotton swab in the broth to disperse the sample and release the microorganisms into the liquid.

f.         Remove the cotton swab from the broth.

g.       Place the swab back into the wrapper it came in.

h.       Close the broth tube with its cap securely.

4.       Cleanup

a.       Properly dispose of used swabs and any other contaminated materials according to laboratory guidelines.

b.       Clean and sterilize all reusable equipment, such as the swab, in preparation for future experiments.

Streaking

Isolation Streaking or Quadrating

1.       Ensure the Bunsen burner is set up on a stable, heat-resistant surface and ignited according to laboratory safety protocols.

a.       Hold the inoculating loop using an appropriate grip and pass it through the flame until it becomes red-hot.

b.       Allow the loop to cool for a few seconds by holding it in a non-contaminated area (e.g., sterile bench or a heat-resistant pad).

2.       Lift the lid of the sterile nutrient agar plate just enough to access a portion of the agar surface.

a.       Use the cooled and sterilized inoculating loop to streak the first quadrant of the agar plate.

b.       Close the lid of the agar plate.

c.        Flame the loop.

d.       Rotate the agar plate 90 degrees clockwise or counterclockwise (whichever is comfortable for you) and lift the lid to access the next quadrant.

e.       Streak the second quadrant using the same inoculating loop, but this time streaking some of the cells from the first quadrant into the second.

f.         Close the lid of the agar plate.

g.       Repeat steps 2a to 2f for the third and fourth quadrants, ensuring to streak cells from the previous quadrants into the next one, follow Figure 7.

h.       Flame the inoculating loop or needle again to sterilize it.

3.       Incubate the streaked or quadrated agar plate at the appropriate temperature for the microorganisms you are working with.

a.       Allow the plate to incubate undisturbed for a suitable period, typically 24 to 48 hours, depending on the growth rate of the microorganisms.

4.       After incubation, observe the agar plate for the presence of isolated colonies or well-separated quadrants.

a.       Count and analyze the colonies or quadrants to determine the level of isolation achieved.

5.       Properly dispose of any used cultures or contaminated materials according to laboratory guidelines.

a.       Clean and sterilize the inoculating loop or needle for future use.

Lawn Creation

1.       Ensure that the Bunsen burner is set up on a stable, heat-resistant surface and ignited according to laboratory safety protocols.

a.       Wipe down the laboratory bench with alcohol or disinfectant wipes to create a clean and sterile workspace.

2.       Label the sterile nutrient agar plate with the necessary information, including the date, bacterial strain, and any other relevant identifiers.

a.       If using a liquid bacterial culture, gently mix it by vortexing or inverting the tube to ensure even distribution of the microorganisms.

b.       If using colonies from an agar plate, pick a well-isolated colony with an inoculating loop and suspend it in a suitable volume of sterile broth to create a homogeneous liquid culture.

3.       Set the pipette to the desired volume (100 μl) using the pipette pump.

a.       Attach a sterile pipette tip to the end of the pipette.

4.       Open the sterile nutrient agar plate and position it on the laboratory bench, ensuring the lid remains partially closed to minimize the risk of contamination.

a.       With the pipette or pipette pump, gently flood the surface of the agar plate with the bacterial culture.

b.       Be careful not to press the pipette tip into the agar, as this may damage the surface and affect the results.

c.        Dip a lawn tool into ethanol then flame off the excess, use the lawn tool to spread the culture around the entire plate.

d.       Ensure that the entire agar surface is covered, leaving no dry spots.

5.       An alternate method is, to use a sterile loop to spread the culture across the entire plate, then rotate the plate approximately a third around, then repeat the streak, turn again and streak again.  See Figure 8.

6.       Close the agar plate securely and incubate it at the appropriate temperature for the specific bacterial strain being used.

7.       Properly dispose of any used pipette tips and other contaminated materials according to laboratory guidelines.

a.       Clean and sterilize all reusable equipment, such as the pipette and pipette pump.

Lab Exercise

Objective

The purpose of this lab is to provide students with hands-on practice in various microbial transfer techniques commonly used in a microbiology laboratory. Students will learn how to transfer Escherichia coli (E. coli) from stock broth to agar plates, inoculate broth cultures, transfer colonies from plates to slant tubes, and perform a lawn technique using a pipette on an agar plate.

Materials

·         Escherichia coli (E. coli) stock broth culture

·         Sterile nutrient agar plates

·         Sterile nutrient agar slant tubes

·         Sterile broth tubes

·         Inoculating loops

·         Inoculating needles

·         Bunsen burner

·         Pipettes

·         Pipette pump

·         Sterile pipette tips

·         Test tube or bottle rack

·         Sterile cotton swabs

Procedure

Preparation

1.       Arrange all the required materials and equipment on the laboratory bench.

2.       Label each plate, slant tube, and broth tube appropriately to avoid confusion during the transfer process.

3.       Ensure that the Bunsen burner is set up safely on a heat-resistant surface.

Inoculating Broth Culture (Plate to Broth)

1.       With the sterile cooled inoculating loop, gently pick up a single colony from the E. coli stock agar plate.

2.       Open an E. coli stock broth tube and insert the inoculating loop into the broth.

3.       Gently rotate the loop in the broth to disperse the colony and release the microorganisms.

4.       Carefully remove the loop from the broth and close the broth tube with its cap.

5.       Incubate the broth tube at the appropriate temperature.

a.       Record results

Cloudiness of broth before incubation

________________________________________

Predicted appearance of broth after incubation

________________________________________

Actual appearance of broth after incubation

_________________________________ 

Transfer colonies from Stock Broth to Agar Plate (Isolation Quadrating)

1.       Flame the inoculating loop until it becomes red-hot and allow it to cool.

2.       Open the stock E. coli broth culture and a sterile agar plate.

3.       Use the inoculating loop to streak the E. coli culture onto the agar plate in a quadrant streaking pattern. Repeat this process for each quadrant of the plate.

4.       Flame the inoculating loop until it becomes red-hot and allow it to cool.

5.       Open the stock M. luteus broth and a sterile agar plate.

6.       Use the inoculating loop to streak the M. luteus culture onto the agar plate in a quadrant streaking pattern. Repeat this process for each quadrant of the plate.

7.       Incubate the agar plates upside-down at the appropriate temperature.

a.       Record results

Inoculate Deep (Broth to Deep)

1.       Flame the inoculating needle until it becomes red-hot and allow it to cool.

2.       Open a stock E. coli broth tube and insert the inoculating needle into the broth.

3.       Flame the neck of the sterile agar slant tube and insert the inoculating needle into the deep agar, pushing the needle to the bottom to create a deep inoculation.

4.       Close the slant tube with its cap and incubate it at the appropriate temperature.

a.       Record results

Transfer Colonies from Plate to Slant Tube

1.       Flame the inoculating loop until it becomes red-hot and allow it to cool.

2.       Open the stock agar plate and select a well-isolated colony of E. coli.

3.       Use the inoculating loop to pick up the colony and transfer it into the sterile agar slant tube.

4.       Gently streak the loop back and forth along the slant, from bottom of the slant to the top.

5.       Close the slant tube with its cap and incubate it at the appropriate temperature.

a.       Record results

Perform a Lawn Technique using a Pipette on an Agar Plate

1.       Set the pipette to the desired volume (100 μl) using the pipette pump.

2.       Flame the pipette tip briefly to sterilize it.

3.       Open a sterile nutrient agar plate and gently flood the surface with E. coli culture.

4.       Use the lawn tool to spread the culture evenly across the agar surface, creating a lawn.

5.       Incubate the agar plate at the appropriate temperature.

a.       Record results

Mixed Culture Separation

1.       Flame the inoculating loop until it becomes red-hot and allow it to cool.

2.       Open the stock mixed broth and the sterile agar plate.

3.       Use the inoculating loop to streak the mixed culture onto the agar plate in a quadrant streaking pattern. Repeat this process for each quadrant of the plate.

4.       Incubate the agar plate upside-down at the appropriate temperature.

a.       Record results

b.       Compare the colonies on the mixed isolation quadrant plate to the E. coli and M. luteus individual plates.

5.       Pick an individual isolated E. coli colony from the mixed plate and streak it on to half of a sterile plate.

6.       Flame the inoculating loop until it becomes red-hot and allow it to cool.

7.       Pick an individual isolated M. luteus colony from the mixed plate and streak it on to the other half of the sterile plate.

8.       Incubate the agar plate upside-down at the appropriate temperature.

a.       Record results

b.       Did you create pure cultures?

Observed E. coli Traits

Size

Texture

Transparency

Pigmentation

Whole Colony

 _________________________________________________

 Observed M. luteus Traits

Size

Texture

Transparency

Pigmentation

Whole Colony

 _________________________________________________

Cleanup

1.       Properly dispose of all used cultures and contaminated materials according to laboratory guidelines.

2.  Clean and sterilize all reusable equipment, such as inoculating loops, needles, and pipettes.